Version July 2025
INTRODUCTION —
Preeclampsia is a progressive multi-system disorder that manifests after 20 weeks of gestation or soon after giving birth; the diagnostic criteria are listed in the table (table 1). The disorder is mediated by the placenta. In some patients, a mismatch between maternal blood supply and fetal demand occurs because cytotrophoblast cells fail to adequately remodel the uterine spiral arteries into highly dilated vessels at 8 to 18 weeks of gestation (the blueprint for early-onset preeclampsia). In other patients, preexisting maternal vascular disease results in placental dysfunctional changes (the blueprint for late-onset preeclampsia). The resultant relative placental ischemia and oxidative stress lead to an imbalance of trophoblast-derived angiogenic modulators in the maternal circulation, with increased concentrations of anti-angiogenic factors (soluble fms-like tyrosine kinase 1 [sFlt-1] and soluble endoglin [sEng]) and reduced concentrations of pro-angiogenic factors (vascular endothelial growth factor [VEGF] and placental growth factor [PlGF]). Increased placental mass (eg, multiple gestation, gestational trophoblastic disease) can also lead to similar changes in concentrations of anti-angiogenic and pro-angiogenic factors. These changes in circulating angiogenic modulators lead to widespread vascular inflammation and diffuse endothelial dysfunction, resulting in the maternal end-organ injuries and the clinical findings characteristic of the disorder. Preeclampsia always eventually resolves after the patient gives birth, although complications (eg, stroke) can still occur in the postpartum period. The pathogenesis of preeclampsia is reviewed in more detail separately. (See "Preeclampsia: Pathogenesis".)
A key challenge in prenatal care is the ability to accurately identify patients at high risk for developing preeclampsia, ideally early in pregnancy so that interventions to prevent or mitigate the disease process and prepare the patient can be implemented. This topic will discuss approaches to the prediction of preeclampsia in asymptomatic patients. These approaches are based on the pathophysiology described in the above paragraph. Issues related to the prevention, diagnosis, and management of preeclampsia (including a detailed discussion of the use of agents such as low-dose aspirin [LDA]) are reviewed separately.
●(See "Preeclampsia: Clinical features and diagnosis".)
●(See "Preeclampsia: Antepartum management and timing of delivery".)
●(See "Preeclampsia: Intrapartum and postpartum management and long-term prognosis".)
●(See "Preeclampsia: Prevention".)
RATIONALE FOR IDENTIFYING HIGH-RISK PATIENTS
In early pregnancy — Accurate early pregnancy identification of patients at high risk of developing preeclampsia has two main benefits:
●Selecting appropriate patients for initiation of low-dose aspirin (LDA) prophylaxis – Administration of LDA can significantly reduce the frequency of preeclampsia and its associated maternal and perinatal morbidity and mortality in patients at high risk of developing the disorder, but this benefit has not been proven in the general (average-risk) obstetric population [1-9]. Thus, it is important to accurately identify high-risk patients. Early identification is also important because LDA prophylaxis appears to be most effective if initiated early in gestation (ideally at 11 to 14 weeks [10]); administration after 16 weeks confers little, if any, protection [1,11-17].
Of note, LDA is most effective for reducing the risk of preterm preeclampsia, with no or minimal effects on term preeclampsia [18]. Preterm preeclampsia is associated with higher rates of adverse maternal and perinatal outcomes than term preeclampsia; however, in absolute terms, most complications occur in term preeclampsia since it is more common [19]. (See "Preeclampsia: Prevention", section on 'Low-dose aspirin'.)
●Patient preparation – Preparing the patient for a pregnancy potentially complicated by preeclampsia may involve referral to a physician with expertise in the management of the disease, more than routine counseling about its signs and symptoms, home blood pressure monitoring, and/or more frequent prenatal visits [17,20]. In addition, patients who know that they are at high risk of developing preeclampsia have an opportunity to think about their choice of settings for prenatal care and giving birth. Those initially planning to receive pregnancy care and give birth in a low-risk setting (eg, midwifery practice, birthing center, home birth) may choose to switch their care to a higher level of care setting or plan in advance for a transition to a higher level of care setting if preeclampsia develops. Lastly, patients who know they are high risk are more likely to adhere to LDA prophylaxis [21].
In mid- to late pregnancy — Accurate identification of patients at high risk of developing preeclampsia in mid- to late pregnancy has a different focus since it is too late for any intervention (other than delivery) to prevent the development of preeclampsia or mitigate its severity. The potential benefit at this stage of pregnancy is to increase the chance of early diagnosis since preeclampsia can quickly progress to a severe condition with serious adverse outcomes. Early diagnosis improves maternal and perinatal outcomes if it leads to timely and appropriate management, which may involve increased maternal and fetal surveillance, antenatal corticosteroids to promote fetal lung maturation, treatment of severe hypertension (if present) to prevent maternal stroke, magnesium sulfate prophylaxis (when indicated) to prevent seizures, and/or early delivery [22].
The same biochemical marker tests used to predict preeclampsia in asymptomatic patients can also be used in symptomatic patients to support the diagnosis of preeclampsia and predict its progression and outcome. This information can be helpful in symptomatic patients since the management and prognosis of preeclampsia is not the same as that for chronic or gestational hypertension. In addition, identifying preeclamptic patients at risk for progression to preeclampsia with severe features can be helpful in decision-making regarding hospitalization versus outpatient care and timing of delivery. These clinical scenarios are discussed in detail separately. (See "Preeclampsia: Clinical features and diagnosis", section on 'Role of measurement of angiogenic markers' and "Preeclampsia: Antepartum management and timing of delivery", section on 'Role of sFlt-1:PlGF'.)
STRATEGIES FOR IDENTIFYING HIGH-RISK PATIENTS
Assessment of historic and demographic risk factors alone — This strategy evaluates a patient's risk status based only on assessment of demographic and historic risk factors for preeclampsia; these risk factors vary somewhat among guidelines (table 2). The goals are to identify patients who will benefit from low-dose aspirin (LDA) prophylaxis and stratify the intensity of prenatal care based on preeclampsia risk. However, use of historic risk factors alone predicts less than 50 percent of patients who will develop preeclampsia and has a high (>60 percent) screen-positive rate [23,24].
The rationale for limiting preeclampsia prediction to only historic and demographic risk factors is that, although more complex risk-prediction models have higher detection rates, the positive predictive values of such models are still low and the models require that all pregnant patients undergo laboratory and Doppler imaging tests. This extra testing potentially exposes a large number of patients to tests that will not benefit them and will worry them about a disorder they will not develop for a small absolute reduction in preeclampsia [25,26]. Furthermore, the laboratory and imaging tests can be complicated and costly to implement in the overall obstetric population. Although some cost-effectiveness analyses demonstrated reduced prevalence of preterm preeclampsia and cost savings associated with first-trimester prediction of preeclampsia coupled with early use of LDA in individuals at high risk [27-29], others have not established this as the most cost-effective option [30]. (See 'Multi-test and computational risk prediction modeling' below and 'Tests used in risk prediction' below.)
Recommendations of selected medical societies are summarized below and in the table (table 3):
●The American College of Obstetricians and Gynecologists (ACOG), the Society for Maternal-Fetal Medicine (SMFM), the National Institute for Health and Care Excellence (NICE), and the International Society for the Study of Hypertension in Pregnancy (ISSHP) recommend using the historic- and demographic-risk-factor-only approach in singleton pregnancies to identify high-risk patients [25,31,32]. Reaffirmed in 2023, ACOG specifically states that "…biomarkers and ultrasonography cannot accurately predict preeclampsia and should remain investigational" [25].
●The International Federation of Gynaecology and Obstetrics (FIGO) recommends this approach only in low-resource settings where it is not possible to measure biochemical markers (eg, placental growth factor [PlGF]) and/or perform uterine artery Doppler velocimetry [10]. FIGO also recommends that baseline risk assessment should be a combination of maternal risk factors plus mean arterial pressure (MAP), rather than maternal risk factors alone.
Multi-test and computational risk prediction modeling — Multiple investigators have evaluated combinations of historic, demographic, laboratory, and/or imaging variables in logistic regression analysis to create tools to predict an individual patient's risk of developing preeclampsia. In general, the sensitivity and specificity are better for predicting early-onset (<34 weeks) than late-onset preeclampsia [25]. This is expected given the difference in pathophysiology between the two disease entities. (See 'Introduction' above.)
Fetal Medicine Foundation calculator (11+0 to 14+1 weeks) — The Fetal Medicine Foundation (FMF) risk for preeclampsia online calculator is probably the most commonly used complex tool for first-trimester assessment of preeclampsia risk. It uses a combination of [33-36]:
●Maternal characteristics – Obtained from the medical and obstetric histories and physical examination. An advantage of the FMF calculator is that it also includes protective factors, such as whether a previous pregnancy was not complicated by preeclampsia.
●Biophysical measurements – Mean uterine artery pulsatility index [UTPI]) and/or MAP (See 'Tests used in risk prediction' below.)
●Biochemical markers – PlGF or, if unavailable, pregnancy-associated plasma protein A [PAPP-A] can be used, but detection of preterm preeclampsia is reduced. Both PlGF and PAPP-A require population-based normalization, although a nonlinear machine-learning-based approach has been developed that uses raw biomarker data without the need to convert into multiples of the median (MoM) [37]. (See 'Tests used in risk prediction' below.)
It is estimated that 250 individuals need to be assessed in the first trimester to prevent one case of preterm preeclampsia, assuming that those identified as high risk (≥1 in 100) begin and adhere to LDA prophylaxis [38].
In a systematic review of validation studies, the detection rate for prediction of preeclampsia ranged from 75 to 92 percent at a screen-positive (fasle-positive) rate of 10 percent [39]. The largest study assessing the performance of the FMF calculator included over 61,000 pregnant patients and 1770 cases of preeclampsia [23]. Detection rates for early (<32 weeks), preterm (<37 weeks), and term (≥37 weeks) preeclampsia were approximately 90, 75, and 41 percent, respectively, at a screen-positive rate of 10 percent. By comparison, detection rates by maternal factors alone were 53, 45, and 34 percent, respectively. The FMF model for predicting preterm preeclampsia performed better than other models in a meta-analysis of externally validated prediction models, with a pooled area under the receiver-operating-characteristics curve (AUC) of 0.90 [40]. The other models generally had poor-to-good discrimination performance, median AUC 0.66.
In addition, a meta-analysis evaluating the use of first-trimester screening algorithms for predicting preeclampsia (primarily the FMF calculator) combined with use of preventive therapy (LDA) in high-risk patients found that this approach was associated with a 39 percent reduction in the prevalence of preeclampsia <37 weeks compared with routine prenatal care (0.45 versus 0.70 percent; odds ratio [OR] 0.61, 95% CI 0.52-0.70) and with a 62 percent reduction in the prevalence of preeclampsia before 32 to 34 weeks (0.14 versus 0.41 percent; OR 0.38, 95% CI 0.22-0.64) [41]. The results were consistent across the six observational studies and one large randomized trial. A retrospective cohort study comparing use of the FMF calculator (136 patients) with maternal risk factors alone (278 patients) found that the tool was associated with a higher sensitivity (55.6 versus 36.9 percent) and higher specificity (92.0 versus 84.1 percent) for identifying patients who developed preterm preeclampsia, had fewer screen positives (8.2 versus 16.1 percent), increased targeted aspirin use among patients classified as high risk (99.0 versus 28.9 percent), and was associated with a reduction in the overall rate of preeclampsia (2.8 versus 3.6 percent), with the largest relative reduction for early preeclampsia [21].
Recommendations of selected medical societies are summarized below and in the (table 3):
●The FMF, FIGO, and the International Society of Ultrasound in Obstetrics and Gynecology (ISUOG) guidelines recommend using the FMF calculator for first-trimester preeclampsia risk prediction [10,42]. The main basis for their endorsement is the evidence described above showing a reduction in preeclampsia with use of a first-trimester screening algorithms for predicting preeclampsia (eg, FMF calculator) combined with use of preventive therapy (LDA) in high-risk patients.
Fetal Medicine Foundation calculator (19+0 to 24+6 weeks or 30+0 to 37+6 weeks) — Online FMF calculators are also available for use at 19+0 to 24+6 weeks and 30+0 to 37+6 weeks. In contrast to the early pregnancy calculator, these calculators include soluble fms-like tyrosine kinase 1 (sFlt-1) and do not have the option of substituting PAPP-A for PlGF. Compared with first-trimester assessment, these calculators may have superior predictive value for identifying patients at high risk of developing preterm and term preeclampsia since predictive tests typically perform better when used closer to the time of disease manifestation [43,44]. However, whether improved prediction at this stage of pregnancy leads to a reduction in adverse pregnancy outcome has not been determined.
In one study from a research group in England, combined screening (maternal factors, MAP, UTPI, and PlGF) between 19 and 24 weeks of gestation predicted 99 percent of early preeclampsia (<32 weeks), 85 percent of preterm preeclampsia (<37 weeks), and 46 percent of term preeclampsia, with a 10 percent screen-positive (false-positive) rate, which was superior to the detection rates achieved by maternal demographic characteristics and medical history alone (52, 47 and 37 percent, respectively) [45]. In another study from this group, combined screening (maternal factors, MAP, UTPI, PlGF, and sFlt-1) between 30 and 34 weeks predicted 98 percent of preterm preeclampsia (<37 weeks) and 49 percent of term preeclampsia [46]. In a third study from this group, the highest detection rate for term preeclampsia was 70 percent, achieved at 35 to 37 weeks [47]. Use of UTPI was not useful at 35 to 37 weeks as it did not improve detection of patients who would develop term preeclampsia. None of these studies reported other pregnancy outcomes so it is not known if the information resulted in less maternal and fetal/newborn morbidity.
Recommendations of selected medical societies:
●There are no specific recommendations from national consensus bodies regarding screening for preeclampsia risk in the late-second and/or third trimesters of pregnancy. Screening asymptomatic patients should not be confused with testing patients with "suspected preeclampsia," who have signs and/or symptoms of the disease. In patients presenting with signs and/or symptoms suggestive of preeclampsia, use of circulating angiogenic factors (sFlt-1/PlGF ratio, PlGF alone) with or without clinical characteristics can facilitate accurate second- or third-trimester diagnosis of both early- and late-onset preeclampsia [48,49]. (See "Preeclampsia: Clinical features and diagnosis", section on 'Role of measurement of angiogenic markers'.)
TESTS USED IN RISK PREDICTION —
Multiple laboratory and imaging tests have been used singly or in combination to help identify patients at high risk for developing preeclampsia. Some tests have been used in the general obstetric population and others have been used to better define risk in patients identified as high risk based on historic and demographic information. Each of these tests and their utility in predicting preeclampsia are discussed separately below.
●Uterine artery Doppler velocimetry – Impedance to flow in the uterine arteries normally decreases as pregnancy progresses. Increased impedance for gestational age is an early radiographic feature of preeclampsia and likely reflects high downstream resistance due to suboptimal remodeling of the maternal spiral arteries, with failure of these arteries to transform into low-resistance vessels. Based on these observations, two types of uterine artery Doppler waveform analysis findings have emerged for prediction of preeclampsia, as well as other disorders associated with impaired placentation (eg, fetal growth restriction, pregnancy loss): (1) diastolic notching (unilateral, bilateral) of the uterine arcuate vessels and (2) abnormal waveform indices and ratios (eg, resistance or pulsatility index greater than the 90th centile for gestational age [10,50]).
The value of uterine artery Doppler velocimetry depends on the population being tested and whether the goal is identification of any preeclampsia or preeclampsia with severe features. In a meta-analysis of uterine artery Doppler ultrasonography to predict development of preeclampsia [51]:
•In the overall obstetric population, preeclampsia was best predicted by an increased uterine artery pulsatility index (UTPI) with diastolic notching in the second trimester (>16 weeks; positive likelihood ratio 7.5, 95% CI 5.4-10.2; negative likelihood ratio 0.59, 95% CI 0.47-0.71). Preeclampsia with severe features was best predicted by an increased UTPI (positive likelihood ratio 15.6, 95% CI 13.3-17.3; negative likelihood ratio 0.23, 95% CI 0.15-0.35) and bilateral notching (positive likelihood ratio 13.4, 95% CI 8.5-17.4); negative likelihood ratio 0.4 (95% CI 0.2-0.6). Doppler testing was less accurate in the first trimester.
•In patients at high risk of developing preeclampsia based on historic and demographic factors, preeclampsia was best predicted by unilateral notching (positive likelihood ratio 20.2, 95% CI 7.5-29.5; negative likelihood ratio 0.17, 95% CI 0.03-0.56) and an increased pulsatility index with notching (positive likelihood ratio 21.0, 95% CI 5.5-80.5; negative likelihood ratio 0.82, 95% CI 0.72-0.93). Prediction of preeclampsia with severe features showed low diagnostic characteristics (positive likelihood ratio 3.7). Doppler testing was less accurate in the first trimester.
Although meta-analyses show that uterine artery Doppler analysis can predict patients at increased risk of preeclampsia [51-53], typically, uterine artery Doppler findings are not interpreted alone, but rather in combination with other clinical/demographic risk factors, serum biomarkers, and other ultrasound measurements. (See 'Multi-test and computational risk prediction modeling' above.)
●PlGF (pro-angiogenic factor) – In normal pregnancy, circulating levels of the pro-angiogenic factor placental growth factor (PlGF) increase from week 11 to 12, peak at 30 weeks, and then decrease to term [54]. Individuals who develop preterm preeclampsia have significantly lower first-trimester PlGF levels than those with normal pregnancies, and a significant association exists between lower serum PlGF levels in early pregnancy and the severity of preeclampsia (defined by gestational age at the time of iatrogenic delivery and neonatal birth weight percentile) [43,55]. The threshold for high versus average risk for developing preeclampsia depends on the specific commercial PlGF test used [56].
When PlGF is used alone, the detection rates for early- and late-onset preeclampsia are 55 and 33 percent, respectively, at a fixed false-positive rate of 10 percent [55]. These rates are less than those with the FMF calculator described above, which incorporates multiple demographic, biochemical, and biophysical parameters. (See 'Fetal Medicine Foundation calculator (11+0 to 14+1 weeks)' above.)
●sFlt-1 (anti-angiogenic factor) – Circulating levels of the anti-angiogenic factor soluble fms-like tyrosine kinase 1 (sFlt-1) only increase disproportionally after 22 weeks of gestation in patients at high risk of developing preeclampsia but can predate the clinical syndrome by several weeks [54,57]. sFlt-1 is not measured as a stand-alone test, instead the sFlt-1:PlGF ratio is calculated. Since sFlt-1 increases and PlGF decreases in patients with preeclampsia, a high sFlt-1:PlGF ratio is predictive of the disorder. The threshold for a high versus average risk for developing preeclampsia depends on the specific commercial sFlt-1:PlGF test used [56].
●Pregnancy-associated plasma protein-A (PAPP-A) – In the first trimester, a low PAPP-A (<5th percentile and not associated with aneuploidy) has been associated with an increased risk of developing preeclampsia (OR 1.94, 95% CI 1.63-2.30), with a detection rate of 16 percent (range, 9 to 28 percent) at 8 percent false-positive rate in a systematic review [58]. As such, it has limited utility as an isolated marker for preeclampsia prediction but may be used an adjunct biomarker in a multi-marker algorithms. (See 'Fetal Medicine Foundation calculator (11+0 to 14+1 weeks)' above.)
●Other
•Cell-free DNA (cfDNA) and RNA – Increasing evidence suggests that early pregnancy-circulating cfDNA and cfRNA may be useful biomarkers for predicting adverse pregnancy outcomes, including preeclampsia [59-69]. Further research is needed.
•Uric acid – Circulating levels of uric acid are elevated in patients with preeclampsia. The mechanism is not well understood but is likely related to the effect of preeclampsia on maternal kidney function. Not only might uric acid be an important biomarker for preeclampsia prediction and diagnosis, but it may also play a role in the pathogenesis of maternal and fetal complications. It is a potent inhibitor of endothelial function, induces systemic hypertension in animals, and is capable of both blocking trophoblast invasion in vitro as well as VEGF-mediated endothelial proliferation.
Although elevated levels of uric acid in patients presenting with elevated blood pressure after 20 weeks confers an eight- to ninefold risk for preeclampsia [70], the clinical utility of this biomarker has been challenged as a number of studies have suggested that the predictive value of serum uric acid is relatively poor both for diagnosis and prognosis, especially for distinguishing preeclampsia from gestational hypertension. One setting in which it may be useful is in assessing disease severity and predicting the latency period (time from diagnosis to delivery) [48,71]. More research is needed.
•Maternal hemodynamic parameters – In a prospective study, patients who developed preterm or any-onset preeclampsia often exhibited increased systemic vascular resistance and decreased cardiac output before 16 weeks of gestation compared with those who did not [72]. Although these changes may reflect early cardiovascular maladaptation associated with preeclampsia, the information did not enhance the screening performance of the FMF calculator (maternal factors, mean arterial pressure, uterine artery pulsatility index, and placental growth factor).
LIMITATIONS OF AVAILABLE DATA —
Accurate identification of patients at high versus average risk of developing preeclampsia is difficult because the prevalence of preeclampsia in the general obstetric population is relatively low (1 to 7 percent), with the majority of those developing term rather than preterm preeclampsia. Given the low prevalence of preeclampsia, most screening tests will have low positive predictive values, even with excellent sensitivity and specificity [7,25]. Systematic reviews and expert opinions have generally concluded that available tests are not sufficiently accurate for use in the general obstetric population [10,38,73-80]. The utility of available data on prediction of preeclampsia has been limited by several factors, including (1) variation in the definition of preeclampsia, which introduces heterogeneity in the classification of the syndrome; (2) variation in inclusion/exclusion criteria, which also increases heterogeneity; (3) variation in the criteria defining level of risk (high versus average) of a given population (some studies of average-risk populations have had preeclampsia incidence rates higher than high-risk populations in other studies); (4) multiplicity of potential tests, test combinations, and timing of screening during pregnancy; (5) lack of inclusion of specific important information; and (6) flawed study design and/or conduct [81,82].
Also, data on preeclampsia risk stratification in multifetal pregnancies are limited. While the same first-trimester tests used to screen singleton pregnancies have been adapted for use in twin pregnancies, comparable detection rates can only be achieved at the cost of high screen-positive rates [10].
OUR APPROACH
●We suggest using the early pregnancy FMF online calculator or a similar calculator that involves a combination of historic/demographic risk factors, mean arterial pressure (MAP), uterine artery pulsatility index (UTPI), and biomarkers (placental growth factor [PlGF] and/or pregnancy-associated plasma protein A [PAPP-A]) to identify patients in early pregnancy (ideally at 11 to 13 weeks of gestation) at high risk of developing preeclampsia (≥1 in 100 [10]). This approach has the best performance for identifying such patients with an acceptable screen-positive rate (around 10 percent).
●Patients who screen positive (high-risk) through the use of the early pregnancy FMF calculator or a similar calculator are started on low-dose aspirin (LDA) as soon as possible and before 16 weeks [18]. We use 100 to 150 mg daily through 36 weeks of gestation. (See "Preeclampsia: Prevention", section on 'Low-dose aspirin'.)
●Counseling all patients about the signs and symptoms of preeclampsia and monitoring all patients for development of the disease is a routine component of prenatal care, but we provide more intense counseling and more frequent monitoring for high-risk patients than for average-risk patients. After 20 weeks of gestation, this may include more frequent maternal blood pressure measurements and review of symptoms, and fetal growth scans every three to four weeks.
●We screen each patient only once during the pregnancy, given absence of evidence that repeat testing later in pregnancy improves any outcome.
●If preeclampsia develops, we discontinue LDA and begin standard management. (See "Preeclampsia: Antepartum management and timing of delivery" and "Preeclampsia: Intrapartum and postpartum management and long-term prognosis".)
In settings where it is not feasible to obtain UTPI or biomarker testing, an acceptable alternative approach would be to use the American College of Obstetricians and Gynecologists (ACOG)-recommended "historic and demographic" screening method (which uses the factors in the table (table 2)) with or without MAP in early pregnancy to identify patients at high risk for developing preeclampsia and starting them on LDA prophylaxis. Patients who screen positive (high-risk) should also receive personalized counseling about the disorder and more frequent prenatal care (eg, blood pressure measurement, symptom review, ultrasound to assess fetal growth).
We do not screen patients who present for prenatal care too far along in pregnancy to benefit from LDA prophylaxis (ie, beyond 16 weeks).
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: Hypertensive disorders of pregnancy".)
SUMMARY AND RECOMMENDATIONS
●Rationale for screening to predict future preeclampsia – Accurate early pregnancy identification of patients at high risk of developing preeclampsia enables selection of appropriate patients for initiation of low-dose aspirin (LDA) prophylaxis to reduce the risk of development of preterm preeclampsia. It also enables patient preparation for a pregnancy potentially complicated by preeclampsia, which may involve referral for consultation with a physician with expertise in the management of the disease, more than routine counseling about its signs and symptoms, home blood pressure monitoring, more frequent prenatal visits, and the opportunity to think about their choice of setting for prenatal care and giving birth. (See 'In early pregnancy' above.)
Screening in late pregnancy may increase the chance of early diagnosis of preeclampsia. (See 'In mid- to late pregnancy' above.)
●Identification of patients at high risk of developing preeclampsia – For all pregnant patients, we suggest routine screening with a comprehensive risk assessment to identify patients <16 weeks of gestation at high risk for developing preeclampsia (Grade 2C). Risk assessment is made ideally at 11 to 13 weeks of gestation and incorporates all of the following:
•Maternal medical and obstetric history and demographic risk factors (table 2)
•Biophysical measurements (eg, mean arterial blood pressure [MAP], uterine artery pulsatility index [UTPI])
•Biochemical markers (eg, PlGF, pregnancy-associated plasma protein A [PAPP-A])
The Fetal Medicine Foundation (FMF) online calculator or a similar calculator can be used to estimate the risk. We consider patients with a ≥1 in 100 chance for developing preterm preeclampsia high risk. (See 'Our approach' above and 'Fetal Medicine Foundation calculator (11+0 to 14+1 weeks)' above and 'Assessment of historic and demographic risk factors alone' above.)
We screen each patient only once in early pregnancy, given absence of evidence that repeat testing later in pregnancy improves any outcome. (See 'Our approach' above.)
●Low-dose aspirin (LDA) prophylaxis – Patients who screen positive (high-risk) are started on LDA as soon as possible and before 16 weeks. We use 100 to 150 mg daily through 36 weeks of gestation. The evidence for use of LDA to reduce the risk of preeclampsia is discussed separately. (See "Preeclampsia: Prevention", section on 'Low-dose aspirin'.)
If preeclampsia develops, we discontinue LDA and begin standard management. (See "Preeclampsia: Antepartum management and timing of delivery".)
