Fertility and pregnancy after bariatric surgery

INTRODUCTION — Bariatric surgery has become an increasingly utilized and effective approach for achieving sustainable weight loss, as well as reducing morbidities associated with severe obesity. More than 80 percent of bariatric procedures are performed in women, and approximately half of these are performed in reproductive aged women [1]. Thus, it has become increasingly common for women who have undergone bariatric surgery to present for preconceptional counseling or prenatal care.

The data presented in this topic review have been derived from retrospective studies, case reports, and personal experience. There are no available data from randomized trials or prospective cohort studies. Other issues related to obesity and bariatric surgery are discussed separately.

●(See "Obesity in adults: Overview of management".)

●(See "Bariatric surgery for management of obesity: Indications and preoperative preparation".)

●(See "Bariatric procedures for the management of severe obesity: Descriptions".)

In this topic, when discussing study results, we will use the terms "woman/en" or "patient(s)" as they are used in the studies presented. However, we encourage the reader to consider the specific counseling and treatment needs of transmasculine and gender expansive individuals.

BARIATRIC SURGERY

Types of procedures — Bariatric surgical procedures can be divided into malabsorptive, restrictive, and combined types (table 1). This difference is based upon the anatomic configuration of the procedure, which in turn contributes to the mechanisms by which they induce weight loss. Roux-en-Y (combined mechanism) and sleeve gastrectomy (restrictive) are commonly performed. (See "Bariatric procedures for the management of severe obesity: Descriptions".)

Clinical implications — It is important for the clinician to know which procedure a patient has undergone to facilitate accurate counseling about potential complications and reproductive issues, as well as possible interventions. The type of surgery also appears to impact subsequent pregnancy outcomes. (See 'Pregnancy outcomes' below.)

Multiple anatomic and physiologic changes that occur after bariatric surgery can affect absorption of medications [2]. As examples:

●Gastric-band procedures – If the patient has undergone placement of a laparoscopic adjustable gastric band procedure, the volume of fluid within the band can be adjusted during pregnancy to help manage pregnancy-related nausea and vomiting and prevent excessive or inadequate gestational weight gain [3,4]. The band is tightened by adding more fluid to a reservoir attached to the band, which creates increased pressure and tightens the band. The band is loosened by removing fluid from the reservoir, which reduces pressure in the band and loosens it. The best management of the gastric band during pregnancy has not been determined and there is variation in care [5].

●Malabsorptive procedures – Procedures that create malabsorption, such as biliopancreatic diversion, jejunoileal bypass, or Roux-en-Y bypass, may interfere with the absorption of oral contraceptives, thereby reducing their effectiveness. (See 'Contraception' below.)

●Restrictive procedures – Restrictive procedures result in a small gastric pouch that may increase the risk of gastric ulceration from drugs such as nonsteroidal anti-inflammatory agents, which are commonly used for treatment of dysmenorrhea and postpartum pain [6]. Use of drugs associated with gastric irritation should be avoided or minimized.

●Combined procedures – Reduction in functional intestinal length leads to faster transit time and less time for slow absorption [6]. Therefore, combination restrictive-malabsorptive procedures reduce absorption of extended release formulations. These formulations should be avoided, if possible; an immediate release formulation is preferable.

●Implications for therapeutic drug levels – When using oral medications in which a therapeutic level is critical, drug levels should be monitored [2,7]. Dosing of common medications (eg, antibiotics, anticoagulants) after bariatric surgery is described in detail separately. Discussions on medication management and management of medical disorders are discussed separately. (See "Bariatric surgery: Postoperative nutritional management" and "Intensive care unit management of patients with obesity".)

FERTILITY BEFORE AND AFTER SURGERY — Obesity can be associated with oligoovulation/anovulation, as well as a reduced response to fertility treatment. In addition, even in eumenorrheic women, obesity is associated with a longer time to pregnancy despite the same coital frequency [8-10]. Obesity also reduces male fertility parameters [11]. (See "Obesity in pregnancy: Complications and maternal management".)

Both nonsurgical [12] and surgical weight loss can improve fertility [3,13-19]. This was illustrated in a series in which 15 of 32 women who were unsuccessful in their attempts to conceive prior to bariatric surgery became pregnant following surgery [14].

In different reports, women who conceived following bariatric surgery had infertility rates of 15 to 44 percent prior to surgery [3,15,16]. Return to fertility can be rapid, as all 24 oligomenorrheic women in one series resumed normal menstrual cycles after a mean of 3.4±2.1 months postoperatively [17]. Postsurgical weight loss improves multiple hormonal changes related to polycystic ovary syndrome (PCOS) (eg, insulin resistance, androgen levels), thereby reducing anovulation and enhancing the potential for conception [17,20-22]. In one study, 70 of 98 anovulatory women regained normal menstrual cycles after surgery [18]. The patients who resumed ovulation lost significantly more weight than those who remained anovulatory.

In spite of these encouraging data, most experts agree that bariatric surgery is not indicated as a primary treatment of infertility in severely obese women [23,24]. In women who remain infertile after surgery, in vitro fertilization could be considered. If indicated, it can be safe and successful, but experience is limited to case reports [25].

TIMING OF CONCEPTION FOLLOWING SURGERY — Several clinical practice guidelines, including by the American Association of Clinical Endocrinologists, the Obesity Society, the American Society for Metabolic & Bariatric Surgery, and others, recommended that patients avoid conception for 12 to18 months after bariatric surgery [26,27]. We generally advise women to delay pregnancy for 12 to 24 months following bariatric surgery because this time frame is when they are actively losing the most weight [11,28-31]. This delay is done in an effort to optimize weight loss and reduce the potentially adverse effect of post-bariatric surgical nutritional deficiencies [14,32]. Since evidence supporting this approach is limited, counseling should be individualized [31,33]. As an example, patients who undergo gastric banding procedures typically lose weight more gradually than gastric bypass patients. The band can be adjusted if weight loss is deemed too rapid or excessive [3]. These factors might reduce the concern about conception during the rapid weight loss phase.

While the optimal interval from bariatric surgery to conception is not known, it is reasonable to advise delaying pregnancy for 24 months after a bariatric procedure based upon the following data:

●Effect on neonatal outcome – In the largest cohort study comparing neonatal outcomes from over 1850 women grouped by the elapsed time from bariatric surgery to birth, higher rates of prematurity (17 versus 12 percent), neonatal intensive care unit admission (18 versus 12 percent), and small for gestational age status (13 versus 9 percent) were reported for infants born less than two years from bariatric surgery compared with infants born more than four years after surgery [34]. These data were adjusted for maternal body mass index (BMI), hypertension, and diabetes and the model addressed known confounders such as maternal age, race/ethnicity, educational level, parity, and annual household income. The women in the study had multiple types of bariatric procedures, including banded gastroplasty, adjustable gastric banding, sleeve gastrectomy, or Roux-en-Y gastric bypass.

Of note, these findings contrast with data from much smaller observational studies (range of 34 to 489 pregnancies after bariatric surgery) that suggested that time from bariatric surgery to birth did not impact neonatal complications [35-39]. The difference in the study sizes is a likely contributor to the outcomes differences. Type of bypass procedure may play a role as well. More data are needed to understand the surgical and postoperative variables that impact pregnancy outcome and whether or not the data are the same for all types of bariatric procedures.

●Effect on gestational weight gain and short-term postpartum weight loss – Time to conception after surgery may affect gestational weight gain and postpartum weight loss, but studies have reported discordant results [3,35,36]. In one such study, women who conceived within 12 months of surgery had less weight gain during pregnancy and less weight loss postpartum than those who waited longer before conceiving (mean gestational weight gain (1.8 versus 15.5 kg [4 versus 34 pounds]); mean postpartum weight loss (6.4 versus 9.5 kg [14 versus 21 pounds]) [36].

●Long-term effect on total weight loss – Only limited data are available on the long-term effects of time to conception after surgery on total weight loss. In one study of timing of pregnancy and weight loss, pregnancy during the phase of rapid weight loss did not negatively affect total weight loss: total weight loss in women who conceived before and after 12 months averaged 45 and 51 kg (99 and 113 pounds), respectively, and the final BMI was also similar for both groups (33 and 31 kg/m², respectively) [36]. In another study of the effect of pregnancy on weight loss at a median 30 months post-bariatric surgery, women who became pregnant during this interval lost the same percentage of excess weight as women who did not become pregnant (70 percent); the interval between bariatric surgery and first pregnancy was a median 11 months [40].

CONTRACEPTION — Contraceptive counseling is an important consideration for all reproductive-aged females undergoing bariatric procedures. This is especially important for adolescents in whom pregnancy rates following surgery are twofold higher than in the general adolescent population [41]. While this increase is probably due in large part to enhanced fertility associated with weight loss, Roux-en-Y gastric bypass also appears to reduce absorption of oral contraceptives.

However, despite recommendations for contraception use during the first 12 to 18 months following surgery, many patients do not use contraception. In a prospective cohort study of 710 women of reproductive age who underwent bariatric surgery, 4 percent actively tried to conceive, and 41 percent had unprotected intercourse while not trying to conceive during the first postsurgical year [42]. Risk factors for not using contraception included advancing age, being married or cohabitating, and preoperatively rating future pregnancy as important. This study highlights the need for careful preoperative contraception counseling and continued postoperative counseling to avoid rapid conception during the first postoperative year.

The American College of Obstetricians and Gynecologists recommends using non-oral forms of hormonal contraception in females who have undergone malabsorptive bariatric surgery and desire hormonal contraception [28]. The Centers for Disease Control and Prevention (CDC) Medical Eligibility Criteria for Contraceptive Use give recommendations for use of all contraceptive methods [43,44]. We support continued use of non-hormonal and progestin-only contraceptives in otherwise healthy patients with obesity following bariatric surgery. Individuals with additional risk factors for venous thromboembolism (eg, smoking) or who desire estrogen-containing contraceptives should be individually counseled regarding risks, benefits, and alternatives. Contraceptive options for patients with obesity are discussed in detail separately. (See "Contraception: Counseling for females with obesity", section on 'Contraception pre- and post-bariatric surgery'.)

PREGNANCY OUTCOMES

Summary — The impact of bariatric surgery on pregnancy must be weighed against the risks of untreated obesity in pregnancy.

●Impact of untreated obesity – Obesity is associated with numerous adverse pregnancy outcomes, including miscarriage, preeclampsia, gestational diabetes, macrosomia, cesarean delivery, stillbirth, and possibly congenital anomalies. Obesity also increases the risk of maternal complications of pregnancy, including venous thromboembolism and infections such as chorioamnionitis, endometritis, and wound disruption. (See "Obesity in pregnancy: Complications and maternal management".)

●Obstetric outcomes

•Improved outcomes – Studies have reported reduced risks of gestational diabetes, large for gestational age (LGA) or macrosomic infant, gestational hypertension, chorioamnionitis, and surgical site infection for patients undergoing prepregnancy bariatric surgery [45-49]. Cesarean delivery rates are similar or reduced after bariatric surgery.

•Worsened outcomes – Prepregnancy bariatric surgery is associated with increased risk of small for gestational age (SGA) infant, but the increase in SGA risk appears to be of smaller magnitude compared with the much lowered risk of having an LGA infant [45-52]. (See 'Fetal growth restriction' below.)

•Unclear impact – Conflicting data have been reported on the risk of neonatal intensive care unit admission for babies born to individuals who have undergone prepregnancy bariatric surgery [45,46]. While prepregnancy bariatric surgery is associated with a reduction in all hypertensive disorders of pregnancy, data on the risk of preeclampsia are mixed, although the largest study reported a benefit with surgery [46,50]. (See 'Preeclampsia and other hypertensive disorders of pregnancy' below.)

●Impact of procedure type – The type of bariatric surgery appears to impact pregnancy outcomes. A network meta-analysis specifically comparing Roux-en-Y with sleeve gastrectomy procedures reported Roux-en-Y was associated with greater reductions in LGA infants, gestational hypertension/preeclampsia, and gestational diabetes but greater increases in small for gestational age (SGA) infants [53]. This finding was similar to an earlier meta-analysis that reported malabsorptive procedures were less likely to give birth to LGA infants and but more likely to have an SGA infant compared with patients undergoing restrictive procedures [50].

●Impact of comparator group – After bariatric surgery, the frequencies of many adverse outcomes are reduced below those in obese women who have not undergone bariatric surgery [50,54-56]. Sometimes they are reduced to the frequency of adverse events that occur in patients without obesity. The magnitude of the effect of surgery on pregnancy outcomes varies based on the control group selected (general obstetric population, obese women who have not undergone surgery, or pre- versus post-bariatric surgery pregnancy outcomes in the same group of patients).

Miscarriage — Although nonsurgical weight loss may reduce the risk of miscarriage [12], available data on the impact of bariatric procedures on miscarriage rate have not consistently shown a benefit. Data are limited by small sample size and/or design deficiencies [14,57].

Gestational diabetes — Observational and case-control studies consistently report a lower prevalence of gestational diabetes mellitus (GDM) among women who have had bariatric surgery than among obese women who have not undergone this surgery [46,48,54,58], although the prevalence of GDM after bariatric surgery remains higher than that of the general obstetric population [3,55,59-63].

●General risk reduction – A meta-analysis of over 2.8 million pregnant women, including over 8300 women who had undergone bariatric surgery, reported an 80 percent reduced risk of gestational diabetes following bariatric surgery compared with control women who were matched for preoperative body mass index (BMI; odds ratio [OR] 0.20, 95% CI 0.11-0.37, number needed to benefit = 5) [50].

●Same-patient risk reduction – A study of 3686 patients who experienced pregnancy before and after bariatric surgery reported a 60 percent reduction in the risk of gestational diabetes (odds ratio 0.39, 95% CI 0.35-0.45) [48]. The study design in which each patient functioned as their own control reduced potential confounders that may exist in studies with different populations.

Women with a history of type 2 diabetes prior to bariatric surgery may become euglycemic following surgery since weight loss improves peripheral insulin sensitivity [64].These women may remain euglycemic during pregnancy, despite pregnancy-related insulin resistance [65].

Women with a history of bariatric surgery who develop GDM appear to have similar perinatal outcomes and glycemic control as other women with GDM [7]. It is unclear whether the type of bariatric procedure impacts the course and outcome of GDM.

Preeclampsia and other hypertensive disorders of pregnancy — While bariatric surgery is associated with a reduction in all hypertensive disorders of pregnancy, data on its impact for the risk of preeclampsia are mixed and limited to observational data [46,50,55,59,66]. However, the larger studies reported a benefit and an earlier meta-analysis reported a trend toward reduced risk, although statistical significance was not achieved [46,49,50].

●In a retrospective study of over 20,000 deliveries in a California health system comparing individuals who had undergone bariatric surgery with those who were eligible but declined, bariatric surgery reduced the risk of preeclampsia by nearly half (adjusted odds ratio 0.53, 95% CI 0.46-0.61) [46]. Nearly 10 percent of patients (1886/20,213) had undergone bariatric surgery of various types. Adjusted confounders included age, race/ethnicity, education, median household income, prenatal care, parity, smoking during pregnancy, gestational weight gain, maternal medical comorbidities, and prior history of the outcome.

●In a meta-analysis comparing pregnant women who underwent bariatric surgery with pregnant individuals matched for preoperative BMI, the rates of preeclampsia were statistically similar between the surgery and non-surgery groups (pooled odds ratio 0.59, 0.32-1.09, 179 surgical patients versus 283 control patients, 3 studies) [50]. However, the trend favored risk reduction, all but one included study reported a beneficial effect with prepregnancy bariatric surgery, and the risk of all hypertensive disorders was lower in the bariatric surgery group (odds ratio 0.38, 95% CI 0.27-0.53, 686 surgical patients versus 584 control patients, 4 studies, number needed to benefit 8).

Preterm delivery — Obese women are at higher risk for medically indicated preterm delivery than nonobese women, and bariatric surgery may lower the frequency of preterm births that result from medical complications associated with obesity (eg, hypertensive diseases) [55]. However, bariatric surgery also appears to be an independent risk factor for preterm delivery, although the available evidence is mixed [34,45,55,67-70]. Potential sources of discrepant data include study design and size, type of bariatric surgery (malabsorptive or restrictive), comparator group (preoperative versus prepregnancy BMI), and type of preterm birth (medically indicated versus spontaneous). One study noted that among 326 women who had primary bariatric surgery between a first and second pregnancy, there was a 63 percent reduction in spontaneous preterm delivery (OR 0.37, 95% CI 0.16-0.86) [71].

The above meta-analysis including over 8300 pregnant women who underwent bariatric surgery reported a 35 percent increase in risk of preterm birth (OR 1.35, 95% CI 1.02-1.79, number needed to harm = 35), defined as gestational age <37 weeks, compared with control women who were matched for preoperative BMI, but it did not distinguish between medically indicated and spontaneous preterm deliveries [50]. Three large cohort studies that were not included in the previous meta-analysis also reported an increased risk of delivery <37 weeks for women who underwent bariatric surgery compared with women without surgery who were matched for both preoperative and prepregnancy BMI [34,68,69]. However, in one of the cohort studies, the increased risk of preterm delivery applied only to moderately preterm deliveries (between 32 and 36 weeks 6 days of gestation) and to spontaneous preterm births (ie, not medically indicated preterm births) [69]. These studies contrast with the results of a prior a systematic review and two smaller cohort studies that reported no increased risk of preterm delivery after bariatric surgery [55,67,70].

Until further data are available, we counsel women that bariatric surgery may be an independent risk factor for spontaneous preterm delivery; however, the degree of this risk would not warrant avoidance of surgery nor the preemptive administration of antenatal corticosteroids. (See "Obesity in pregnancy: Complications and maternal management".)

Birth weight — Observational studies have generally reported a reduction in mean birth weight resulting in a larger proportion of appropriate for gestational age (AGA) infants among post-bariatric surgery pregnancies compared with obese women who have not undergone a bariatric procedure [14,37,62,72].

Large for gestational age or macrosomia — Maternal obesity is an established risk factor for delivering an LGA infant [73]. Most observational studies have reported that post-bariatric surgery reduction in BMI reduces the risk of delivering LGA or macrosomic infants [14,45,46,48,49,55,58,60,62,70,74]. However, the benefit of prepregnancy weight loss to reduce the risk of LGA infant may be reversed with excessive pregnancy-related weight gain [75].

●In a retrospective study of over 20,000 deliveries in a California health system comparing individuals who had undergone bariatric surgery (n = 1883) with those eligible for surgery but who declined (n = 18,327), prepregnancy bariatric surgery reduced the risk of LGA neonate by nearly 80 percent (adjusted odds ratio [aOR] 0.23, 95% CI 0.19-0.29) and the risk of macrosomia by 75 percent (aOR 0.23, 95% CI 0.19-0.29) [46].

●A meta-analysis of three studies reported a 30 percent reduction in risk of LGA and macrosomic infants compared with control women matched for preoperative BMI [50].

•For LGA, pooled odds ratio 0.31, 95% CI 0.17-0.59, 830 treated versus 3094 control patients, number needed to benefit = 6.

•For macrosomia, pooled odds ratio 0.32, 95% CI 0.11-0.89, 1123 cases versus 2965 control patients, number needed to benefit = 13.

Fetal growth restriction — Initial observational studies reported increased rates of fetal growth restriction (FGR) and small for gestational age (SGA) infants in post-bariatric surgery patients, particularly if conception occurred within two years of surgery, but data from individual studies have been inconsistent [3,14,48,49,58,63,70,74,76,77]. The discrepant results may have reflected small sample sizes, heterogeneous study designs, and lack of matching for preoperative BMI given that systematic reviews have generally demonstrated increased risk of SGA [50-52].

●Increased risk – A meta-analysis including over 8300 pregnant women who underwent bariatric surgery reported more than double the risk of FGR (OR 2.16, 95% CI 1.34-3.48, number needed to harm = 66) and SGA infants (OR 2.16, 95% CI 1.34-3.48, number needed to harm = 21) compared with control patients matched for preoperative BMI [50].

●Impact of procedure type – Malabsorptive procedures appear to increase the risk of SGA infants while restrictive surgeries do not [50]. In a study of 139 pregnant persons who had undergone bariatric surgery, SGA occurred in 29 percent of malabsorptive procedures, 9 percent of restrictive procedures, and 6 percent of control patients [77].

●Impact of maternal gestational weight gain – Maternal weight gain during pregnancy appears to confound the risk of having an SGA infant. In a study of 127 post-bariatric pregnancies, the risk of SGA was 15 percent for patients with adequate weight gain compared with 74 percent for those with inadequate gain [75].

Cesarean delivery — Observational studies of cesarean delivery rates in post-bariatric surgery pregnancies have reported higher cesarean rates than in the general obstetric population [37,59]. This is not unexpected since both age and obesity are risk factors for cesarean delivery. Women who undergo bariatric procedures are typically older and more likely to be obese than women in the general obstetric population [7,78]. Cesarean delivery rates tend to be either similar to or lower than rates in obese women who have not undergone bariatric surgery [37,46,50,58,60,70].

Perinatal morbidity and mortality — Although there are conflicting data, bariatric surgery does not appear to greatly increase the risks of perinatal morbidity and mortality and appears to lower the risk of neonatal skeletal injuries, likely through reducing the risk of LGA infants [48].

●Gestational age at delivery – In the largest retrospective study that compared 670 women who had undergone bariatric surgery prior to pregnancy with up to five control pregnancies matched for the mother's preoperative BMI, there was no difference in the rates of preterm delivery among the women, although the bariatric surgery group had a four-day-shorter mean gestational age [67].

●Stillbirth or perinatal death – The risk of the combined outcome of stillbirth or neonatal death was higher after bariatric surgery than for the control group (1.7 versus 0.7 percent) in the retrospective study of 670 patients, but this difference was not statistically significant. A smaller retrospective chart review reported a nearly eightfold increased risk of perinatal death after bariatric surgery compared with no surgery, but the study included only 70 women who had undergone bariatric surgery, which makes the validity of this finding questionable [63].

●Other

•Increased risk – One observational study that used patients as their own controls by comparing birth outcomes before and after bariatric surgery reported more than double the risk of bronchiolitis-associated respiratory failure following bariatric surgery (adjusted analysis, odds ratio 2.42, 95% CI 1.76-3.36) [48]. This finding warrants further study as obesity, and not weight loss, has been associated with increased bronchiolitis incidence and severity [79].

•No change in risk – Earlier observational studies did not demonstrate any correlation between prior bariatric surgery and low Apgar scores, meconium-stained amniotic fluid, or perinatal mortality rate [23,55,59,70,80].

•Reduced risk – Prepregnancy bariatric surgery was associated with an approximately 70 percent reduction in skeletal birth injury (odds ratio [OR] 0.27, 95% CI 0.11-0.60), febrile convulsions (OR 0.39, 95% CI 0.21-0.67), viral intestinal infections (OR 0.56, 95% CI 0.43-0.72), and carbohydrate metabolism disorders in the newborn (OR 0.54, 95% CI 0.46-0.63).

Congenital anomalies — The risk of congenital anomalies does not appear to be increased for women who have undergone bariatric surgery [19,50,81-84]. Challenges in interpreting the data include the limitations of observational studies, inclusion of multiple surgeries with different mechanisms of weight loss (restrictive, malabsorptive, or combined procedures), and use of different comparator groups (untreated obese women or normal-weight women). Examples of representative studies include the following:

●A nationwide Swedish matched cohort study that compared pregnancy outcomes of nearly 3000 women who underwent Roux-en-Y bariatric surgery with obese women who did not undergo bariatric surgery reported a reduced risk of congenital anomalies following bariatric surgery (incidence 3.4 versus 4.9 percent, respectively, risk ratio 0.67, 95% CI 0.52-0.87, risk difference -1.6 percent, 95% CI -2.7 to -0.6) [81]. Control women were propensity matched for congenital anomalies in prior pregnancies, preoperative BMI, diabetes, maternal age, medical comorbidities, and medication and/or substance use. While this finding is reassuring, the generalizability of this study to women who have undergone other bariatric procedures is not known.

●A Canadian cohort study that compared over 1800 women with any type of bariatric surgery with both obese and nonobese control women initially reported an increased risk of congenital anomalies for women who underwent prepregnancy bariatric surgery compared with having no surgery or obesity (relative risk [RR] 1.20, 95% CI 1.01-1.43) [84]. However, this association went away after controlling for folic acid supplementation (risk ratio 1.05, 95% CI 0.86-1.28). By contrast, obese women continued to have an increased risk of congenital anomalies, even after folic acid fortification was mandated (RR 1.13, 95% CI 1.09-1.17). There was also no association between different surgery subtypes and risk of anomalies. Limitations of the study include the wide time range (1989 to 2016), during which many changes were implemented in the care of pregnant women following bariatric surgery, and the inclusion of multiple procedure types. The study controlled for maternal age, medical comorbidities, socioeconomic status, and folic acid exposure.

Specific concerns had been raised by several case reports regarding a possible association between bariatric surgery and neural tube defects [82,83]. There is a biologic plausibility of folate deficiency and hyperhomocysteinemia following bariatric procedures [3,82,85]. However, in the above Swedish cohort study, all neural tube defects occurred in the matched obese control group, and none occurred in the infants born following bypass surgery [81]. Any potential increased risk of neural tube defects in post-bariatric surgery patients must be balanced with the increased risk of congenital anomalies seen in overweight and obese women [86]. Adequate folic acid supplementation (800 mcg daily) during pregnancy in gastric bypass patients may reduce the risk of neural tube defects and is strongly encouraged. (See 'Micronutrient supplementation' below.)

The various types of bariatric surgery and mechanisms of action are presented in detail separately. (See "Bariatric procedures for the management of severe obesity: Descriptions".)

PRENATAL CARE — General aspects of prenatal care are discussed in detail separately. (See "Prenatal care: Initial assessment".)

The following discussion applies to issues specific to pregnant women who have undergone bariatric surgery. Ideally, women planning pregnancy post-bariatric surgery should be co-managed by a bariatric surgeon, dietitian, and obstetrician.

Micronutrient supplementation — Metabolic and nutritional derangements can occur after bariatric surgery, particularly after malabsorptive procedures. Reduced oral intake and alterations in digestive anatomy result in malabsorption of various micronutrients and minerals, particularly iron, folate, vitamin B12, calcium, and vitamin D. Absorption of iron and folate are reduced due to lower acid content in the gastric pouch and bypass of the duodenum, the main site of absorption. Calcium deficiency can also result from bypass of the duodenum, as well as reduced intake of both calcium and vitamin D. A reduction in the availability of both gastric acid and intrinsic factor may lead to B12 deficiency.

While women with prior malabsorptive procedures are at greatest risk for micronutrient deficiencies, women who undergo restrictive procedures may also develop iron, folate, and fat soluble vitamin deficiencies [87]. Further review of these nutritional deficiencies and their management is detailed separately. (See "Bariatric surgery: Postoperative nutritional management".)

A number of adverse pregnancy outcomes have been attributed to inadequate supplementation and resultant micronutrient deficiencies. Iron and B12 deficiencies have resulted in maternal anemia. Case reports have described neural tube defects possibly related to folate deficiency [85], fetomaternal electrolyte imbalances [88], microphthalmia attributed to vitamin A deficiency [89], and fetal cerebral hemorrhage attributed to vitamin K deficiency [90,91]. Wernicke's encephalopathy due to thiamine deficiency is a particular concern in women with hyperemesis gravidarum and gastric bypass.

To reduce the risk of complications from micronutrient deficiency, specific supplementation regimens need to be tailored to the individual patient and the type of bariatric procedure performed [92]. Guidelines for optimum micronutrient supplementation during pregnancy have been extrapolated from data from the bariatric and obstetric literature [27]. In general, during pregnancy, it is reasonable to continue the regimen recommended by the bariatric surgeon, but the multivitamin is replaced with a prenatal vitamin. Total vitamin A intake from all supplements should be limited to 5000 international units per day to avoid retinoid embryopathy [28].

Micronutrient supplementation after Roux-en-Y gastric bypass (RYGB), one of the most common bariatric procedures, should include:

●Vitamin B1 (thiamine) 1.4 mg

●Vitamin D 400 IU

●Vitamin K 120 mcg

●Zinc 11 mg

●Biotin 30 mcg

●Iron 65 mg

●Folate 800 mcg

●Calcium citrate 1200 mg

●Vitamin B12: oral or sublingual 350 to 500 mcg/day; intramuscular 1000 mcg/week; intranasal 500 mcg/week

These daily requirements can typically be met with a prenatal vitamin in addition to calcium and vitamin B12 supplementation. Additional iron and folate may also be required with certain prenatal vitamins. Chewable and liquid prenatal vitamins are an option for women who cannot take a large prenatal vitamin, and may be better absorbed [6]. Other adjustments may also avoid deficiencies due to impaired absorption. Calcium citrate is preferred to calcium carbonate because it is less dependent on gastric acidity for absorption [93]. Oral absorption of vitamin B12 depends on the presence of intrinsic factor; use of non-oral supplements is preferable in women with low intrinsic factor due to partial gastrectomy. Supplementing iron therapy with vitamin C after gastric bypass is more effective in restoring ferritin and hemoglobin than iron alone [94].

We suggest screening for micronutrient deficiencies to individualize therapy and adjust doses as needed. The importance of monitoring was illustrated by a study that observed various micronutrient deficiencies during pregnancy in spite of prophylactic supplementation [95]. We obtain the following laboratory tests preconceptionally or at the first prenatal visit [96]:

●Complete blood count

●Ferritin

●Iron

●Vitamin B12

●Thiamine

●Folate

●Calcium

●Vitamin D

Identified deficiencies should be corrected and monitored with monthly assessments. Further surveillance of blood count, iron, ferritin, vitamin B12, calcium, and vitamin D is performed every trimester [28,96]. Persistent deficiencies should be corrected with increased oral doses or parenteral forms of iron, vitamin B12, and vitamin D. Intravenous (IV) iron is generally preferred over oral iron replacement as it ensures adequate delivery and avoids gastrointestinal toxicities, which may be especially challenging for women who have undergone bariatric surgery and are pregnant. For women who do not have access to IV iron or who have tolerated oral iron supplementation in the past, we add an oral iron supplement to the prenatal vitamin. Oral iron can be dosed daily or every other day based on three small trials of nonpregnant women who had not undergone bariatric surgery that reported once-daily or every-other-day dosing of oral iron may result in equal or better absorption [97,98].

Supplementation and screening should continue following delivery in women who breastfeed. (See 'Postpartum' below.)

Fetal growth assessment — Given the possible increased risk of intrauterine growth restriction and small for gestational age infants in post-bariatric surgery pregnancies, we suggest performing serial ultrasound examinations every four weeks to evaluate fetal growth in the third trimester, especially in women with poor weight gain and those who conceive within two years of surgery. (See 'Fetal growth restriction' above and "Fetal growth restriction: Pregnancy management and outcome", section on 'Prenatal care'.)

Gestational diabetes

Screening — Screening for gestational diabetes is optimally performed at 24 to 28 weeks of gestation. However, it should be done as early as the first prenatal visit if there is a high degree of suspicion that the pregnant woman has undiagnosed type 2 diabetes (eg, marked obesity, personal history of gestational diabetes, glycosuria, or strong family history of diabetes). (See "Gestational diabetes mellitus: Screening, diagnosis, and prevention".)

The glucose challenge test used to screen for gestational diabetes is typically not well tolerated in women with prior RYGB due to dumping syndrome, which occurs in approximately 50 percent of these patients [99]. This phenomenon follows ingestion of food or drinks containing high amounts of refined sugars. As a result of the hyperosmolar environment, fluid shifts rapidly from the intravascular compartment to the small bowel lumen causing distension, cramping, nausea, vomiting, and diarrhea. Tachycardia, palpitations and diaphoresis are also common, and may be related to intravascular depletion or a hyperinsulinemic response and reactive hypoglycemia.

To avoid the possible occurrence of dumping syndrome, we generally recommend that women with RYGB avoid the standard 50 g glucose challenge test used to screen for gestational diabetes. We, along with others, suggest following fasting and postbreakfast blood sugars for one week as an alternative [28,100]. Patients who regularly drink and tolerate sugared soft drinks are an exception; these women probably can tolerate a standard glucose challenge test. A third option is to measure glycated hemoglobin (A1C) and assume overt diabetes is present if it is elevated (≥6.5 percent); women with a normal A1C should undergo screening as described. (See "Gestational diabetes mellitus: Screening, diagnosis, and prevention".)

Dumping syndrome typically does not occur in women who have undergone restrictive-type bariatric procedures such as gastric banding. These women can undergo standard testing for GDM.

Treatment — Although conventional treatment of GDM involves nutritional therapy and insulin, some clinicians use oral anti-hyperglycemic agents, such as glyburide or metformin. If these agents are used, it should be noted that oral agents may not be absorbed completely after RYGB due to bypass of the duodenum [6]. (See "Gestational diabetes mellitus: Glucose management and maternal prognosis" and "Outcomes of bariatric surgery".)

Monitoring for complications of bariatric surgery — The most common late sequelae of bariatric surgery are mild nutritional deficiencies, which are readily treated with replacement therapy. (See 'Micronutrient supplementation' above.)

Small bowel obstruction after RYGB is an uncommon but life-threatening complication that requires a high index of suspicion and early evaluation for the disorder when patients present with often nonspecific abdominal symptoms. (See 'Bowel obstruction' below.)

Bowel obstruction — Numerous case reports have described bowel obstruction during pregnancy in women who had previously undergone bariatric surgery, some resulting in fetal and maternal death [101-110]. A systematic review of 120 patients who required emergency surgery during pregnancy after having had a bariatric procedure included patients with prior RYGB (99), laparoscopic adjustable gastric banding (17), Scopinaro procedure (2), vertical banded gastroplasty (1), and one anastomosis gastric bypass (1) [111]. Complications were described in 50 cases, including internal herniation (26), bowel intussusception (10), intestinal obstruction (2), slippage of laparoscopic adjustable gastric band (3), bowel volvulus (3), gastric or jejunal perforation (2), and other complications (4). There were three maternal deaths and nine fetal deaths. The majority of cases occurred within two years of bariatric surgery, although herniations as far as nine years from the time of RYGB were reported. In a cohort study of pregnant women with obstruction, patients with a previous RYGB bypass were more likely to have an obstruction than those who had not undergone RYGB surgery, which is consistent with the surgical risk from RYGB procedures [112]. These studies highlight the need to evaluate pregnant women who have a history of bypass surgery, particularly RYGB, and who develop new symptoms that could represent bowel obstruction.

●(See "Etiologies, clinical manifestations, and diagnosis of mechanical small bowel obstruction in adults".)

●(See "Large bowel obstruction".)

●(See "Bariatric procedures for the management of severe obesity: Descriptions".)

RYGB procedures create potential internal spaces through which herniation of the small bowel can occur (figure 1). Internal herniation is seen more frequently in patients who have laparoscopic versus open procedures, with rates as high as 5 percent described [113]. While the rate of internal herniation during pregnancy in post-bariatric surgery patients is unknown, increased abdominal pressure and cephalad intestinal displacement associated with the enlarging gravid uterus may contribute to its formation [101]. In a systematic review of 52 cases of internal herniation in pregnant women with prior RYGB procedures, the mean gestational age at diagnosis was in the 28^th week of gestation with a range of ±7.3 weeks [103].

We recommend a low threshold for obtaining abdominal computed tomography in women post-RYGB with abdominal pain because the nonspecific symptoms seen with early bowel obstruction often overlap with common obstetric complaints such as hyperemesis, esophageal reflux, and contractions. In the above systematic review, although all women presented with abdominal pain, 65 percent had nausea and vomiting, and 75 percent had the diagnosis confirmed by imaging [103]. Thus, radiologic studies may not reveal obvious bowel obstruction in patients with internal herniation; therefore, maintaining a high index of suspicion, early placement of nasogastric tube, and consultation with a bariatric surgeon are warranted in patients with gastrointestinal complaints and possibly fever and/or leukocytosis [114]. Exploratory surgery may be necessary. Two reported maternal deaths were associated, in part, with a delay in diagnosis and surgical intervention [101,102]. (See "Bariatric operations: Late complications with subacute presentations".)

Other — Other surgical complications associated with bariatric surgery include gastric band erosion and slippage, anastomotic leaks and bleeding, stomal stenosis, and marginal ulceration. Some of these complications have been reported during pregnancy [115-117]. (See "Bariatric operations: Late complications with subacute presentations".)

The prevalence of cholelithiasis is increased in pregnancy, as well as after RYGB, especially during the period of rapid weight loss [118].

Gestational weight gain — At present, weight gain recommendations for individuals who have undergone bariatric surgery are based on Institute of Medicine (IOM) guidelines, which are based on prepregnancy body mass index (see "Gestational weight gain"). Caloric restriction during pregnancy is not recommended, even if patients continue to be overweight after bariatric surgery, due to concerns that caloric restriction might impair fetal growth [28].

While poor antepartum weight gain has been associated with fetal growth restriction, preterm delivery, and small for gestational age infants in some reports, causality has not been proven [75,119]. We suggest that women who are not achieving the minimum weight gain standards suggested by the IOM (0.5 pound [0.23 kg]/week for obese women in the second and third trimester) undergo ultrasound evaluation of fetal growth and dietary consultation. If adequate caloric intake is confirmed, we do not recommend encouraging the woman to consume significantly more calories. In patients with adjustable gastric bands, the gastric band can be loosened so there is less gastric constriction and oral intake can be increased [3,15,59,120]. If weight gain is excessive, the gastric band can be tightened.

Mode of delivery — Cesarean delivery is performed for standard obstetric indications. Consultation with a bariatric surgeon is advisable if the patient had a complicated bariatric surgery [28]. Patients who have undergone uncomplicated bariatric surgery generally do not require alteration in cesarean delivery technique. Some obstetricians favor blunt entry into the peritoneum to minimize risk of inadvertent injury to bowel that may be adherent to the underlying surface.

Specific recommendations regarding surgical considerations in the obese patient are described elsewhere. (See "Cesarean birth: Overview of issues for patients with obesity".)

Anesthesia for cesarean — In patients who have undergone abdominoplasty, standard methods of assessment of the sensory level of subarachnoid block can be misleading because of dermatomal changes [121,122]. Testing the posterolateral abdomen is more reliable than the anterior abdomen for determining the anesthesia level in these patients, as there is a downward shift in sensory dermatomal level anteriorly. Patients may retain sensation in the anterior abdominal skin despite an adequate posterolateral dermatomal level. Supplemental local anesthesia by the surgeon or a lower surgical incision should then be considered.

POSTPARTUM — Lactation is usually not adversely affected by bariatric surgery and should be encouraged. (See "Maternal and economic benefits of breastfeeding" and "Infant benefits of breastfeeding".)

As discussed above, micronutrient supplementation and screening should continue following delivery in women who breastfeed. Breastfed infants of women who have had gastric bypass procedures may develop nutritional deficiencies, especially those that are exclusively breastfed [123,124].

PATIENT RESOURCE — The American College of Obstetricians and Gynecologists has a free online FAQ sheet for patients that discusses Obesity and Pregnancy.

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Bariatric surgery" and "Society guideline links: Obesity in adults" and "Society guideline links: Pregnancy in women with obesity".)

SUMMARY AND RECOMMENDATIONS

●Clinical implications for females – More than 80 percent of bariatric procedures are performed in females and approximately half of these are performed in reproductive aged individuals. It is important for the clinician to know which specific bariatric procedure a patient has undergone (table 1) in order to counsel about the prevention and management of potential complications and reproductive issues. (See 'Bariatric surgery' above.)

•Pregnancy planning or contraceptive options – Pregnancy planning and contraception options should be discussed with women who undergo bariatric surgery. Fertility improves soon after bariatric surgery, particularly in women who had been anovulatory. (See 'Fertility before and after surgery' above.)

•Efficacy of oral contraceptives - Oral contraceptives may be less effective in women who have undergone malabsorptive bariatric surgery. For women who have undergone these procedures and who desire hormonal contraception, we advise non-oral forms of hormonal contraception. (See 'Contraception' above.)

●Timing of pregnancy – We suggest delaying pregnancy for 12 months following bariatric surgery (Grade 2C). This provides time to optimize weight loss and reduce potential adverse effects of nutritional deficiencies. However, women who conceive proximate to their bariatric surgery can be reassured of a likely favorable pregnancy outcome with optimization of nutrition and careful monitoring and follow-up. (See 'Timing of conception following surgery' above.)

●Impact of bariatric surgery on pregnancy and outcomes – After bariatric surgery, many women have uncomplicated pregnancies and healthy babies, especially if they achieve a normal body mass index.

•Improved or unchanged outcomes – Bariatric surgery likely reduces risk of preeclampsia, gestational diabetes, and macrosomia when compared with obese women who have not undergone a bariatric procedure. The risks of spontaneous preterm delivery, cesarean delivery, and congenital anomalies appear to be the same or lower than in obese women who have not undergone a bariatric procedure, but data are less consistent than for other outcomes. (See 'Pregnancy outcomes' above.)

•Increased risk of fetal growth restriction – Bariatric surgery may increase the risk of intrauterine growth restriction/small for gestational age infant, particularly in women who have undergone gastric bypass procedures. For this reason, we perform serial ultrasound examinations in the third trimester to evaluate fetal growth. (See 'Fetal growth restriction' above and 'Fetal growth assessment' above.)

●Alterations to prenatal care – We refer patients who have undergone a bariatric surgery procedure for preconception or antepartum consultation with a maternal-fetal medicine clinician to discuss potential issues for pregnancy and their management.

•Micronutrient supplementation and testing – We advise micronutrient supplementation and laboratory monitoring for micronutrient deficiencies in pregnancies after any bariatric surgical procedure. This is facilitated by co-management by an obstetrician, bariatric surgeon, and dietitian. (See 'Micronutrient supplementation' above and "Bariatric surgery: Postoperative nutritional management", section on 'Micronutrient management'.)

•Gestational diabetes testing and weight gain – Patients with prior Roux-en-Y gastric bypass (RYGB) should not undergo the 50 g glucose challenge test used to screen for gestational diabetes (GDM), as it is likely to cause dumping syndrome. An exception can be made if the patient regularly drinks sugared soft drinks. We suggest following fasting and postprandial blood sugars for one week as an alternative screening test. (See 'Gestational diabetes' above.)

In patients with adjustable gastric bands, the gastric band can be loosened to facilitate adequate gestational weight gain. (See 'Gestational weight gain' above.)

●Concerns for complications – In women with abdominal pain or other gastrointestinal symptoms, the possibility of a complication of bariatric surgery, such as bowel obstruction, volvulus, or intussusception, must be excluded. We recommend a low threshold for abdominal computed tomography (CT) for evaluation of these women and early consultation with a bariatric surgeon. Exploratory surgery may be necessary, even after a negative CT. (See 'Monitoring for complications of bariatric surgery' above.)

●Mode of delivery – Cesarean delivery is performed for standard obstetric indications. (See 'Mode of delivery' above.)