Uterine fibroids (leiomyomas): Issues in pregnancy

INTRODUCTION — Uterine fibroids (leiomyomas) are benign smooth muscle tumors of the uterus. The potential effects of fibroids on pregnancy and the potential effects of pregnancy on fibroids are a frequent clinical concern since these tumors are common in females of reproductive age. Pain is the most common problem during pregnancy. Although most pregnant individuals with fibroids do not have any complications related to the fibroids during pregnancy, there may a slightly increased risk of obstetric complications, such as early pregnancy loss, preterm labor and birth, fetal malpresentation, and placental abruption, particularly in patients with multiple fibroids, retroplacental fibroids, and fibroids greater than 5 cm in diameter.

This topic will review issues specifically relating to uterine fibroids in pregnancy. Fibroids in nonpregnant females, including fertility issues, are discussed separately.

●(See "Uterine fibroids (leiomyomas): Epidemiology, clinical features, diagnosis, and natural history".)

●(See "Uterine fibroids (leiomyomas): Treatment overview".)

●(See "Female infertility: Treatments", section on 'Fibroids (leiomyoma)'.)

LIMITATIONS OF AVAILABLE EVIDENCE — Several factors make it difficult to assess the impact of fibroids on pregnancy outcome and to identify specific fibroid characteristics that are important [1]. For example, interpretation of available evidence is limited by the heterogeneity of the study populations, which differ in method of ascertainment (eg, prospective versus retrospective study design), gestational age at diagnosis, and fibroid characteristics (number, size, location [fundus, lower uterine segment], type [submucosal, intramural, subserosal; pedunculated or sessile]). Small numbers of adverse events, ascertainment bias in selecting study participants, and inadequate adjustment of confounders also play a role. In addition, small fibroids (<4 to 5 cm) may not be detected consistently because they can be difficult to distinguish from physiologically thickened myometrium. Lastly, the mechanisms whereby fibroids may cause adverse obstetric outcomes are not clearly understood.

EPIDEMIOLOGY — The prevalence of uterine fibroids in pregnancy varies between 1.6 and 10.7 percent, depending upon the trimester of assessment (first versus second), the size threshold for reporting presence of a fibroid (eg, range ≥0.5 to >3 cm), and demographic characteristics of the population [2-7]. (See "Uterine fibroids (leiomyomas): Epidemiology, clinical features, diagnosis, and natural history", section on 'Prevalence'.)

The prevalence increases with maternal age and varies by race. In a prospective cohort study including nearly 2800 patients at 12 clinical sites in the United States, the prevalence of fibroids at any time during pregnancy was 12 percent in patients 19 to 25 years of age, increasing to 32 percent in patients 35 to 42 years of age [7]. The prevalence by race was 9 percent of non-Hispanic White females, 14 percent of non-Hispanic Black females, 6 percent of Hispanic females, and 10 percent of Asian or Pacific Islander females.

Increasing parity and prolonged duration of breastfeeding are associated with a small, but statistically significant, reduction in prevalence [7,8].

CHANGE IN VOLUME DURING PREGNANCY AND POSTPARTUM — Change in fibroid volume during pregnancy may be related to changes in estrogen and progesterone levels, uterine blood flow, and, possibly, human chorionic gonadotropin levels.

●Antepartum – In the prospective cohort study including nearly 2800 patients at 12 clinical sites in the United States discussed above, six obstetric ultrasounds were performed at timed intervals between 10 and 41 weeks of gestation [7]. Change in total fibroid volume was affected by starting volume, showing a strong trend toward increasing among pregnant patients with small volumes (diameter ≤1 cm) at first visualization (mean increase 2.0 percent, 95% CI -0.3 to 4.5 percent per week), no or minimal change among pregnant patients with initially medium volumes (diameter 1 to <3 cm; mean decrease 0.5 percent, 95% CI -2.0 to 1.0 percent per week), and decreasing among pregnant patients with initially large volumes (diameter ≥3 cm; mean decrease -2.2 percent, 95% CI -3.4 to -1.0 percent per week). Change in volume across pregnancy was also affected by maternal characteristics such as age, racial or ethnic ancestry, parity, and miscarriage history.

●Postpartum – Almost 90 percent of patients with fibroids detected in the first trimester will have regression in total fibroid volume when re-evaluated three to six months postpartum, but 10 percent will have an increase in volume [9]. Regression may be less in patients using progestin-only contraception. The effect of breastfeeding on fibroid regression is uncertain [9,10].

SYMPTOMS — Uterine fibroids are usually asymptomatic during pregnancy. In symptomatic individuals, symptoms include pain, pelvic pressure, and/or vaginal bleeding.

Pain is the most common symptom: 11 percent of pregnant individuals with fibroids were admitted to the hospital because of pain in one study [11]. The frequency of pain increases with increasing size and is especially high with large fibroids [3,11,12]. In the same study, 23 percent of patients with fibroids 7 to 10 cm in diameter were admitted for pain [11]. Most patients have only localized pain at the site of the fibroid without other signs and symptoms, although mild leukocytosis, fever, and nausea and vomiting can occur [13,14].

Fibroid pain typically presents in the late first or early second trimester, which corresponds to the period of greatest fibroid growth and, in turn, propensity to degeneration. Pain also may result from partial obstruction of the vessels supplying the fibroid as the uterus grows and changes its orientation to the fibroid or from torsion [15]. (See 'Degeneration and torsion' below.)

Bleeding may occur in early pregnancy if the placenta implants close to the fibroid or later in pregnancy from abruption [16].

Symptoms resulting from ectopic hormone production (eg, erythropoietin [17], parathyroid-related protein [18,19], prolactin) are rare.

COMPLICATIONS THAT MAY BE INCREASED — Most patients do not have any pregnancy complications related to their fibroids [20]. When complications occur, degeneration is most common. Although there appears to be a slightly increased risk of early pregnancy loss, preterm labor and birth, fetal malpresentation, and placental abruption, studies have not consistently reported an increased risk of adverse outcomes [1].

The following list of pregnancy complications begins with those most strongly associated with fibroids and ends with those least associated with fibroids. However, high-quality data on the relationship between fibroids and pregnancy outcome are very limited. (See 'Limitations of available evidence' above.)

Degeneration and torsion — As discussed above (see 'Symptoms' above), pain is the most common symptom of fibroids in pregnant individuals and is typically due to fibroid degeneration or, rarely, torsion. Rapid growth of fibroids can result in a relative decrease in perfusion, leading to ischemia and necrosis (red degeneration) and release of prostaglandins [21]. Pedunculated fibroids are at risk of torsion and necrosis, but this is much less common than degeneration.

The diagnosis of degeneration and torsion is reviewed separately. (See "Uterine fibroids (leiomyomas): Epidemiology, clinical features, diagnosis, and natural history", section on 'Fibroid degeneration or torsion'.)

Early pregnancy loss — In some patients, submucosal fibroids appear to adversely affect implantation, placentation, and ongoing pregnancy. The effects of intramural fibroids are more controversial, while fibroids that are primarily subserosal or pedunculated are unlikely to cause early pregnancy loss. The risk of pregnancy loss may be higher when there are multiple fibroids [22].

The mechanisms by which fibroids may cause pregnancy loss are not known; the following hypotheses have been proposed:

●The fibroid may interfere with placentation and development of normal uteroplacental circulation [23,24]. As an example, a large submucosal fibroid projecting into the uterine cavity may compress the decidualized endometrium, leading to decidual atrophy or distortion of the vascular architecture and blood flow supplying and draining the decidua at that site.

●Rapid fibroid growth with or without degeneration may lead to increased uterine contractility or altered production of catalytic enzymes by the placenta [24,25], both of which may disrupt placentation, leading to pregnancy loss.

When fibroid location was not considered, a meta-analysis of nine cohort studies found no association between fibroid presence and pregnancy loss [26]. These issues are discussed in more detail separately. (See "Female infertility: Causes", section on 'Uterine fibroids (leiomyomata)'.)

Preterm labor and birth — There appears to be an increase in the baseline risk of preterm labor (unadjusted odds ratio [OR] 1.9, 95% CI 1.5-2.3 [27]) and preterm birth (unadjusted OR 1.5, 95% CI 1.3-1.7 [27]) in pregnancies with uterine fibroids [6,27-30]. Characteristics reported to increase this risk include multiple fibroids, placentation adjacent to or overlying the fibroid [11,31,32], and size greater than 5 cm [33]. As with other complications, this association is not consistent across studies [3,34-36]. We do not consider the presence of fibroids alone an indication to monitor cervical length with ultrasound to detect shortening during pregnancy.

Various theories have been proposed to explain the biologic basis of preterm labor in the setting of uterine fibroids. It is possible that fibroid uteri are less distensible than nonfibroid uteri so that contractions occur when the uterus distends beyond a certain point [12,23]. Decreased oxytocinase activity in the pregnant fibroid uterus has been noted, which may result in a localized increase in oxytocin levels, thereby predisposing to preterm contractions [25]. (See "Spontaneous preterm birth: Pathogenesis", section on '#4 Pathologic uterine distention' and "Physiology of parturition at term".)

Placental abruption — In a meta-analysis of three studies with a total of over 170,000 patients, uterine fibroids were associated with more than doubling of the risk of abruption after adjustment of known risk factors (OR 2.29, 95% CI 1.62-2.96) [37].

The location of the fibroid in relation to the placenta appears to be an important determinant. Submucosal and retroplacental fibroids and fibroids with volumes >200 mL (corresponding to 7 to 8 cm diameter) are associated with the highest risk of abruption [3,12,32,38]. As an example, in a retrospective analysis of over 6700 consecutive pregnant patients, 8 out of 14 patients (57 percent) with retroplacental fibroids developed an abruption and four of the eight fetuses died, while only two abruptions occurred among the 79 patients (2.5 percent) whose fibroids were not retroplacental, and neither resulted in fetal death [12].

A hypothesis for the increased risk of abruption in patients with fibroids is that the fibroid adversely affects perfusion of the placental site [12]. When Xenon-133 was used to measure regional blood flow in the uteri of 11 nonpregnant patients undergoing laparotomy, blood flow was significantly reduced in the myometrium adjacent to fibroids [39]. This suggests that the decidua overlying a fibroid may have reduced blood flow, leading to placental ischemia and decidual necrosis, making the area more susceptible to antepartum bleeding and abruption. (See "Acute placental abruption: Pathophysiology, clinical features, diagnosis, and consequences" and "Acute placental abruption: Management and long-term prognosis".)

Malpresentation — Müllerian anomalies are associated with an increased risk of malpresentation, presumably because they distort the shape of the uterine cavity [40,41]. Fibroids that distort the uterine cavity may have a similar effect. In a population-based cohort of over 72,000 consecutive patients with singleton pregnancies in Washington state who underwent a routine second-trimester fetal anatomic survey at a single university hospital, patients with a fibroid uterus were more likely to have a breech presentation at the time of birth compared with those without fibroids (5.3 versus 3.1 percent; adjusted OR 1.5, 95% CI 1.3-1.9) [6].

Large submucosal fibroids that distort the uterine cavity have been consistently associated with an increased risk of fetal malpresentation (unadjusted OR 2.9, 95% CI 2.6-3.2) [27]. Other characteristics associated with a particularly high risk of malpresentation include multiple fibroids, a fibroid located behind the placenta or in the lower uterine segment, or a large fibroid (eg, over 10 cm) [2,12,31,42].

Placenta previa — In a meta-analysis of three studies including a total of over 170,000 patients, uterine fibroids were associated with a more than two-fold increase in risk of placenta previa after adjusting for known risk factors (adjusted OR 2.21, 95% CI 1.48-2.94); the risk was higher with fibroids ≥5 cm (OR 3.53, 95% CI 1.02-6.05) [43].

Dysfunctional labor — Theoretically, fibroids in the myometrium may decrease the force of uterine contractions or disrupt the coordinated spread of the contractile wave, thereby leading to dysfunctional labor and cesarean birth [36,44]. Several studies have reported an increased incidence of dysfunctional labor in pregnancies complicated by fibroids [36,45,46], but not all investigators have been able to confirm this association [2,34].

Higher rates of tachysystole (defined as >5 contractions in 10 minutes) have also been reported [47].

Cesarean birth — Studies have consistently reported that uterine fibroids are associated with an increased risk of cesarean birth (unadjusted OR 3.7, 95% CI 3.5-3.9 [27]), especially when the fibroids are located in the lower uterine segment [2,12,13,31,36,45,46,48-50]. The increase in cesarean birth rate is likely due to multiple factors, such as increased risks of malpresentation (see 'Malpresentation' above), dysfunctional labor (see 'Dysfunctional labor' above), obstruction of the birth canal, and fetal heart rate abnormalities related to abruption (see 'Placental abruption' above). However, most of these studies were biased in their selection of cases, so a causal association is unproven.

Postpartum hemorrhage — Several studies have reported an increased risk of postpartum hemorrhage in pregnancies complicated by fibroids [2,27,38,46], especially if the fibroids are at least 3 cm in the largest dimension, located behind the placenta or in the lower uterine segment [21,42,51,52], or the birth is by cesarean [46]. As an example, in a retrospective study including 4421 patients with fibroids and singleton pregnancies, those with medium (5 to 10 cm) and large (>10 cm) fibroids were at increased risk for postpartum hemorrhage requiring red blood cell transfusion compared with those with small fibroids (adjusted OR 1.65, 95% CI 1.19-2.29 and 2.44, 95% CI 1.41-4.23, respectively) [52]. Lower uterine segment fibroid location was another risk factor for postpartum hemorrhage requiring transfusion (OR 1.49, 95% CI 1.05-2.13). However, numerous other studies have found no association between fibroids and postpartum hemorrhage [31,34,36].

Pathophysiologically, fibroids could predispose to postpartum hemorrhage by decreasing both the force and coordination of uterine contractions, thereby leading to uterine atony [44]. This hypothesis is supported by a large retrospective study in which the rate of postpartum hemorrhage was higher in patients with intramural fibroids (8.6 percent) than in those with submucosal and subserosal fibroids (4.7 and 5.6 percent, respectively) [53]. By comparison, the baseline incidence of postpartum hemorrhage in the general obstetric population is 1 to 3 percent of births.

Genome-wide association studies including more than 300,000 females from six Northern European cohorts identified five sequence variants in the progesterone signaling pathway that were associated independently with both postpartum hemorrhage and fibroids, suggesting that these two clinical conditions may share some common genetic traits [54].

Fetal deformities — Spatial restrictions from uterine fibroids can cause fetal deformations, but this is extremely rare. Case reports have described limb reduction defects, congenital torticollis, and head deformities in pregnancies with large submucosal fibroids [55-57].

False-positive noninvasive prenatal screening (NIPS) — Uterine fibroids are known to release cell-free DNA (cfDNA) into the maternal circulation. Although data are limited, there are early signals suggesting that individuals with fibroids may have higher circulating cfDNA levels that dilute the fetal fraction, thereby increasing the likelihood of an indeterminate cfDNA-based NIPS result for fetal aneuploidy [58]. Fibroids may also increase the risk of a false-positive NIPS for subchromosomal aberration and rare autosomal trisomy [59]. Further research is needed to better understand whether this is related to the number and/or size of the fibroids and how this interacts with other variables that are known to effect cfDNA concentration and fetal fraction, such as maternal obesity.  

Other complications — A number of other pregnancy complications have been reported in patients with fibroids, including disseminated intravascular coagulation, spontaneous hemoperitoneum, uterine incarceration, urinary tract obstruction with urinary retention or acute kidney injury, deep vein thrombosis, and puerperal uterine inversion [42,60-63]. (See "Incarcerated gravid uterus" and "Puerperal uterine inversion".)

Pyomyoma (suppurative leiomyoma) is rare [64-68]. Clinical findings may include fever, leukocytosis, tachycardia, pelvic pain, and characteristic features on imaging studies (heterogeneous mass that may contain gas).

Ultrasound surveillance may be required if large or multiple fibroids increase the distance between the upper border of the pubic symphysis and the top of the uterus, which is a crude screening test to detect abnormalities of fetal growth and amniotic fluid volume.

COMPLICATIONS THAT ARE PROBABLY NOT INCREASED

Preterm prelabor rupture of membranes — Pooled cumulative data suggest that fibroids do not increase the risk of preterm prelabor rupture of membranes and may even slightly decrease the risk [27]. However, individual studies have reported conflicting findings [2,3,6,34-36,45,51,69]. The location of the fibroid in relation to the placenta may be an important determinant: the greatest risk of preterm prelabor rupture of membranes appears to be when the fibroid is in direct contact with the placenta [51].

Fetal growth restriction — Fibroids have minimal, if any, effect on fetal growth (unadjusted OR 1.4, 95% CI 1.1-1.7 [27]) [3,12,31,34-36,48,70]. It is possible, however, that large fibroids (greater than 200 mL) may be associated with the birth of a small-for-gestational age infant (<10^th percentile for gestational age) [71]. Routine prenatal physical examination may not detect fetal growth restriction because of uterine enlargement, thus screening for growth abnormalities would require ultrasound examination.

Fetal demise — Rates of fetal demise are not increased in pregnancies complicated by uterine fibroids [45,48].

Preeclampsia — The majority of studies do not support an association between fibroids and preeclampsia [34,35,45], although one study noted that patients with multiple fibroids were significantly more likely to develop preeclampsia than those with a single fibroid (45 versus 13 percent) [34]. The authors suggested that the increased risk was due to disruption of trophoblast invasion by the multiple fibroids leading to inadequate uteroplacental vascular remodeling leading to the development of preeclampsia.

TREATMENT OF PATIENTS WITH PAINFUL FIBROIDS — Painful fibroids are treated with analgesics.

●Mild to moderate pain – We suggest administration of acetaminophen as the initial intervention.

●More severe pain and pain refractory to acetaminophen – These patients can be treated with short-term use of opioids in standard doses or a short course (ideally <48 hours) of nonsteroidal anti-inflammatory drugs (NSAIDs). Hospitalization may be required for pain management [3,34,42,46].

•First-trimester opioid use has been associated with an increased risk of congenital anomalies in some studies, but the data are weak and do not justify withholding these medications when needed to control pain.

•NSAID options include ibuprofen in standard doses [13] or indomethacin 25 mg orally every 6 hours for up to 48 hours [14]. NSAIDs should be limited to pregnancies less than 32 weeks of gestation because of the possibility of inducing premature closure of the ductus arteriosus, neonatal pulmonary hypertension, oligohydramnios, and fetal/neonatal platelet dysfunction [14,72-74]. If the NSAID is continued for >48 hours, weekly sonographic assessment for oligohydramnios and narrowing of the fetal ductus arteriosus should be performed. If either of these findings is noted, the NSAID should either be discontinued or the dose reduced (eg, reduce indomethacin dose to 25 mg every 12 hours). Repeat courses can be given as needed for recurrent episodes of pain. Although first-trimester use of NSAIDs has been associated with pregnancy loss in some studies, the best data do not support an association [75]. (See "Inhibition of acute preterm labor", section on 'Cyclooxygenase inhibitors (eg, indomethacin)' and "Safety of rheumatic disease medication use during pregnancy and lactation", section on 'NSAIDs'.)

●Refractory persistent severe pain – Case reports have described successful use of epidural analgesia for treatment of severe pain refractory to other therapies [76-78].

Fibroid-related pain is not an indication for emergency surgery; however, surgery can be considered if the pain cannot be adequately controlled by other means.

ROLE OF MYOMECTOMY

Indications for preconception myomectomy — Decisions regarding preconception myomectomy are made on a case-by-case basis and depend on several factors, including the age of the patient, past reproductive history, severity of symptoms, and size and location of the fibroids. These issues are reviewed elsewhere:

●(See "Uterine fibroids (leiomyomas): Treatment overview", section on 'Patients desiring fertility'.)

●(See "Recurrent pregnancy loss: Definition and etiology", section on 'Leiomyoma'.)

●(See "Recurrent pregnancy loss: Management", section on 'Uterine abnormalities'.)

Indications for antepartum transvaginal myomectomy — We generally advise against removal of prolapsed fibroids in pregnancy as the risks likely outweigh the benefits, unless there is an easily accessible pedunculated fibroid on a thin stalk. Removal may lead to hemorrhage, membrane rupture, and/or pregnancy loss [79].

The need for resection should be assessed on a case-by-case basis. Clinically significant bleeding, unmanageable pain, urinary retention, and (rarely) infection during pregnancy due to a prolapsed fibroid are reasonable indications for resection.

Case reports have described generally successful transvaginal removal of symptomatic fibroids in pregnancy; heavy and/or persistent vaginal bleeding was the most common symptom prompting removal [79]. The procedure for transvaginal myomectomy depends on the origin of the fibroid (cervix versus submucosa) and thickness of the stalk/base, which can be determined clinically or by transvaginal ultrasound or magnetic resonance imaging, if necessary. (See "Uterine fibroids (leiomyomas): Prolapsed fibroids".)

An asymptomatic lower uterine segment submucosal prolapsed fibroid may become intrauterine with advancing gestation.

Indications for antepartum abdominal myomectomy — There is consensus to avoid myomectomy during pregnancy, especially if an intramyometrial incision is required, unless the procedure cannot be safely delayed, which is extremely rare [3,13,21,36,80-86]. The reason is that inability to control bleeding during intramyometrial myomectomy is a real possibility and may necessitate hysterectomy. These extremely rare scenarios may include an acute abdomen, obstruction, and suspicion of malignancy [87,88].

●Technique – The approach is typically dictated by size, location, and gestational age. In a literature review of 97 antepartum myomectomies, approximately 80 percent were performed by laparotomy and 15 percent by laparoscopy [88]. Almost all of the procedures were performed in the second trimester.

In contrast to intramyometrial myomectomy in nonpregnant patients, in an ongoing pregnancy we would not exteriorize the uterus or place a tourniquet around the cervix or use vasoconstrictive medications for hemostasis (eg, vasopressin injection, vaginal misoprostol) because these procedures could disrupt placental blood flow. We would not enter the uterine cavity because of the risk of rupturing membranes. We would not avoid using electrosurgery in this setting, preferable monopolar (bipolar if laparoscopic approach). We would perform a multilayer closure with a delayed absorption suture to reapproximate the myometrium.

Removal of a pedunculated fibroid, such as for torsion, is less risky. It would involve ligating/electrocoagulating the stalk and removing the fibroid, leaving a long stalk. Intramyometrial dissection and sutures would be unnecessary.

●Outcome — A systematic review that included 97 patients who underwent myomectomy during pregnancy noted the following findings, although data were incomplete in several cases [88]:

•Abdominal pain was by far the most common preoperative symptom, reported by 80 percent of patients, and the most common indication for surgery. The second most common preoperative symptom was fever, which was observed in 12 percent of patients.

•The median gestational age at myomectomy was 16 weeks (range 6 to 26 weeks).

•Three-quarters of patients had removal of a single fibroid; the remainder had multiple fibroids removed.

•The majority of myomectomies (48 out of 66 [73 percent]) were for pedunculated fibroids, but 26 out of 66 (39 percent) cases were intramural.

•The median estimated blood loss was 350 mL (range 30 to 4500 mL). Five patients received transfusions.

•Postoperative outcomes:

-Five pregnancy losses.

-Ninety-two ongoing pregnancies: The mean gestational ages at birth for patients undergoing single versus multiple myomectomy were 37.2 and 36.8 weeks, respectively, and the cesarean birth rates were 51 and 83 percent, respectively.

Most ongoing pregnancies were uneventful. However, one patient developed full thickness myometrial necrosis with abscess formation and exposure of a 7 by 2 cm portion of the amniotic sac after resection of a degenerating pedunculated leiomyoma by monopolar diathermy at 17 weeks. Antibiotic therapy, abscess drainage, and repair of the defect were successful, allowing the patient to give birth at 37 weeks by planned cesarean.

Indications for cesarean myomectomy — Myomectomy may be required at cesarean birth in order to close the hysterotomy. Although we believe that cesarean myomectomy in other cases generally should be avoided, observational data suggest that it is possible without a high risk of life-threatening events as long as the surgeon has appropriate expertise, appropriate patients are selected (eg, symptomatic pedunculated fibroids), and blood products are available. This decision should be made with caution given the biases inherent to observational studies. We avoid intramyometrial myomectomy because of the risk of severe hemorrhage [3,80,89], which is more likely in pregnancy since the term uterus receives almost one-fifth of cardiac output. The technique for cesarean myomectomy is reviewed separately. (See "Uterine fibroids (leiomyomas): Open abdominal myomectomy procedure", section on 'Cesarean myomectomy'.)

In meta-analyses of mostly retrospective studies of patients with fibroids undergoing cesarean, those undergoing concomitant myomectomy had greater drops in hemoglobin (mean difference 0.25 to 0.27 mg/dL), an approximately 40 percent increase in use of blood transfusion, and longer hospital stay [90,91]. A limitation of the analyses is that results were not stratified according to the location and type of the myomas (eg, pedunculated, subserosal, intramural, submucosal), and these characteristics affect the risk of hemorrhage. For example, favorable results have been reported for removal of pedunculated fibroids at the time of cesarean birth. In a series of five myomectomies performed during cesarean, the four pedunculated fibroids were removed without difficulty, while removal of the single nonpedunculated fibroid was associated with severe hemorrhage [46].

DELIVERY

Choosing the route of delivery

Patients without prior myometrial surgery — Most patients with fibroids will have a successful vaginal birth and thus should be offered a trial of labor. Cesarean birth is reserved for standard obstetric indications (eg, malpresentation, failure to progress).

Planned cesarean birth may be considered because of concerns that fetal descent will be obstructed by a fibroid, but should be limited to patients most likely to fail a trial of labor: those with large cervical fibroids or with lower uterine segment fibroids that distort the uterine cavity and are located between the fetal vertex and cervix in the third trimester [92].

Patients with prior myomectomy — Timing and route of delivery must be individualized in these cases based on the degree and location of the prior uterine surgery, as described in the operative report.

●Prior extensive myometrial surgery – Merely entering the uterine cavity does not constitute an extensive myomectomy, which may be considered a myomectomy in which extensive intramyometrial or complete transmyometrial dissection is required for removal of one or several intramural or submucosal fibroids of appreciable size, followed by extensive uterine reconstruction [93,94]; however, there is no standard definition.

In the absence of strong evidence of the absolute risk of rupture in this setting [95], we take a conservative approach and suggest cesarean birth prior to the onset of labor in patients who underwent an extensive or complicated myometrial myomectomy, similar to patients who have had a previous classical cesarean birth. Such patients are delivered at 36+0 to 37+0 weeks of gestation since they appear to be at risk for preterm labor [30]. Patients who underwent substantial but less extensive myometrial surgery may be delivered by cesarean as late as 38+6 weeks [96].

●Prior nonextensive myometrial surgery – For patients who have had minimal myometrial surgery that was unlikely to have significantly compromised the myometrium, we suggest a trial of labor with continuous intrapartum fetal monitoring, early access to obstetric anesthesia, and the ability to perform an emergency cesarean birth, if it becomes necessary.

Patients who have had a pedunculated fibroid removed would not be expected to have compromised the integrity of the myometrium and do not require additional monitoring during labor.

Evidence — The magnitude of the risk of uterine rupture in pregnancies after myomectomy and specific criteria associated with increased risk are difficult to ascertain because of the small number of cases reported and lack of detail about the operative procedures performed. Available data, although limited, suggest that the risk of uterine rupture after myomectomy is not significantly greater than that for a patient attempting trial of labor after cesarean. In a systematic review of studies with at least five cases of pregnancy after myomectomy [97]:

●The overall incidence of uterine rupture after myomectomy was 7 out of 756 or 0.93 percent (95% CI 0.45-1.92 percent)

●The incidence was 0.47 percent (2 out of 426, 95% CI 0.13-1.70 percent) in patients undergoing trial of labor after myomectomy versus 1.52 percent (5 out of 330, 95% CI 0.65-3.51 percent) in those with planned cesarean before the onset of labor; this difference was not statistically significant.

●Six of the seven ruptures occurred in patients who had a prior laparoscopic myomectomy, probably related to the technical challenge and possible inferiority of laparoscopic suturing [98,99].

●All ruptures occurred following myomectomy of an intramural fibroid, although this was not noted to be a significant risk factor for uterine rupture. The uterine cavity was not entered during myomectomy in three cases; this information was not available in the other four cases.

●The ruptures occurred at 24 (twin pregnancy), 25, 30, 32, 36, 37, and 40 weeks of gestation; however, this finding may be biased by scheduled cesarean births at term.

Additional issues in patients with prior myomectomy — Prior hysteroscopic removal of a submucosal fibroid may increase the risk of abnormal placentation, especially placenta accreta spectrum. The risk appears to be low, but data are sparse [100,101].

We suggest that these patients undergo ultrasound evaluation for possible placenta accreta spectrum in the late second or early third trimester. (See "Placenta accreta spectrum: Clinical features, diagnosis, and potential consequences".)

Technical issues at cesarean birth — Patients with large, retroplacental or anterior lower uterine segment fibroids are at increased risk of intrapartum or postpartum hemorrhage at the time of cesarean birth, so appropriate preparations should be taken. (See "Overview of postpartum hemorrhage", section on 'Institutional planning and preparation'.).

●Preoperative placement of two large bore IVs, use of a cell saver, and ready availability of blood products should be considered on a case-by-case basis.

●A vertical (midline) skin incision may be necessary to obtain adequate exposure.

●Ultrasound imaging can be used (either antepartum or intrapartum) to map out the optimal location for the hysterotomy incision at the time of cesarean in patients with large uterine fibroids. Intraoperatively, a sterile probe cover is placed on the ultrasound transducer and sterile gel is applied to the uterine serosa; the best incision site can then be mapped sonographically.

●A posterior or classical hysterotomy are sometimes necessary to avoid large fibroids located in the lower uterine segment. Every effort should be made to avoid transecting a fibroid during hysterotomy as the incision may be impossible to close without first removing the fibroid. Even with myomectomy, it may be impossible to close the incision in such cases, necessitating hysterectomy.

The general procedure for open myomectomy is described separately. (See "Uterine fibroids (leiomyomas): Open abdominal myomectomy procedure", section on 'Procedure'.)

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: Uterine fibroids (leiomyomas)".)

SUMMARY AND RECOMMENDATIONS

●Course of pregnancy – In pregnant patients with small fibroid volume (diameter ≤1 cm) at first gestational visualization, fibroid volume tends to increase during pregnancy. In those with initially medium volumes (diameter 1 to <3 cm), fibroid volume tends to remain stable, and those with initially large volumes (diameter ≥3 cm) tend to have a decrease in volume. Change in volume across pregnancy can also be affected by maternal characteristics such as age, race or ethnicity, parity, and miscarriage history. (See 'Change in volume during pregnancy and postpartum' above.)

Most patients with fibroids do not have any complications during pregnancy related to the fibroids. When complications occur, pain is the most common complication. The frequency of pain correlates with increasing fibroid size. (See 'Complications that may be increased' above and 'Degeneration and torsion' above.)

Size and location appear to be risk factors for pregnancy complications: large size (>3 cm), retroplacental and lower uterine segment location, and/or distortion of the uterine cavity are characteristics that have been associated with an increased risk of miscarriage, placental abruption, fetal growth restriction, hemorrhage, and preterm labor and birth. The presence of multiple fibroids is another risk factor for preterm labor and birth. (See 'Complications that may be increased' above.)

●Treatment of pain – We administer acetaminophen as the initial intervention for mild to moderate pain. Short-term use of opioids in standard doses or a short course of nonsteroidal anti-inflammatory drugs (NSAIDs) can be given when pain is severe or refractory to initial treatment. (See 'Treatment of patients with painful fibroids' above.)

●Role of myomectomy – Every effort should be made to avoid surgical removal of fibroids in pregnancy because of the risk of significant morbidity (hemorrhage). Abdominal myomectomy is performed if the procedure cannot be safely delayed. (See 'Indications for antepartum abdominal myomectomy' above and 'Indications for cesarean myomectomy' above.)

In patients with a prolapsed fibroid, transvaginal resection is reasonable in patients with clinically significant bleeding, unmanageable pain, urinary retention, or infection. (See 'Indications for antepartum transvaginal myomectomy' above.)

●Route of birth – Most patients give birth vaginally. Cesarean birth is performed for standard obstetric indications (eg, malpresentation, failure to progress), including obstruction of the birth canal by a fibroid. (See 'Choosing the route of delivery' above.)

●Cesarean birth – If the uterine cavity was entered during a prior myomectomy or a large number of myomas were removed, we suggest scheduled cesarean birth rather than a trial of labor (Grade 2C). In the absence of these criteria, we manage patients with a prior myomectomy similar to patients who have had a prior cesarean birth. (See 'Patients with prior myomectomy' above.)

•Timing – Scheduled cesarean birth is performed between 37+0 and 38+6 weeks of gestation, although consideration of birth as early as 36 weeks is reasonable for patients with prior extensive myomectomy (analogous to a patient with prior classical hysterotomy).

•Procedure – Every effort should be made to avoid cutting through fibroids at cesarean birth as it can be impossible to close the hysterotomy site if the fibroids are in it. Intraoperatively, a sterile probe cover can be placed on the ultrasound transducer and sterile gel applied to the uterine serosa; the best incision site can then be mapped sonographically. (See 'Choosing the route of delivery' above.)

●Risk for abnormal placentation – Fibroids have been associated with increased risks of placenta previa and abruption. Prior hysteroscopic removal of a submucosal fibroid may increase the risk of placenta accreta spectrum. Although the risk of placenta accreta spectrum after prior myomectomy appears to be low, we suggest ultrasound examination for possible placenta accreta spectrum in the late second or early third trimester. (See 'Placenta previa' above and 'Placental abruption' above and 'Additional issues in patients with prior myomectomy' above.)