We conducted this comparative effectiveness review to support the U.S. Preventive Services Task Force in updating its recommendation on Preeclampsia Screening. The review aim was to compare different approaches to screening for hypertensive disorders of pregnancy including preeclampsia.
We performed comprehensive searches of MEDLINE, PubMed (publisher-supplied only), Embase, and the Cochrane Collaboration Registry of Controlled Trials for studies published between January 1, 2014, and January 4, 2022. A research librarian developed and executed the search strategy. Studies included in the prior review to support the 2015 recommendation and studies referenced in recently published reviews were also considered for inclusion.
We reviewed 6,316 abstracts and assessed 82 full-text articles against predefined inclusion and exclusion criteria. Studies considered for inclusion were randomized controlled trials and non-randomized studies of interventions (NRSI) comparing screening interventions conducted with pregnant and postpartum people, including those at increased risk for hypertensive disorders of pregnancy. Interventions and comparisons of interest included: blood pressure measurement setting (office or home), interval, frequency, or timing; proteinuria assessment setting, interval, or sequence of testing; and personalization of screening based on risk assessment.
We conducted dual independent critical appraisal of all included studies and extracted all important study details and outcomes from fair- and good-quality studies. We narratively synthesized results by key question and type of screening intervention. We graded the overall strength of evidence as high, moderate, low, or insufficient based on criteria adapted from the Evidence-based Practice Center program.
Five fair-quality randomized controlled trials and one fair-quality NRSI with a historical control were included. Three types of screening strategies were compared with usual screening programs: screening programs that incorporated self-measurement of blood pressure (2 studies, N= 2,521), a reduced prenatal visit schedule for people at low risk for complications of hypertensive disorders of pregnancy (3 studies, N= 5,203), and protein urine screening provided only when indicated rather than at every prenatal visit (1 study, N = 2,441). No studies were designed to test screening interventions focused on populations with the highest risks for hypertensive disorders of pregnancy and adverse pregnancy-related health outcomes. One trial (N = 2,441) incorporated home blood pressure measurement into prenatal care and reported health outcomes. Similar proportions of maternal complications related to hypertensive disorders of pregnancy were seen in the home measurement group (15/1209; 1.2%) as in the usual care group (19/1209; 1.6%). The confidence interval for the relative risk spanned null (RR 0.79 [95% CI, 0.40 to 1.55]). Similar proportions of intrauterine growth restriction occurred in the intervention group (104/1249, 8.3%) compared with the control group (87/1235, 7.0%), and the confidence interval again spanned null (adjusted RR 1.15 [95% CI, 0.87 to 1.53]). The trial also did not report a difference in the timing of detection of high blood pressure. Increased anxiety, a potential harm of home blood pressure measurement, was assessed in two trials and was not associated with the intervention. Three trials published in 1996 and 1997 compared reduced prenatal visit schedules, which result in fewer antenatal blood pressure assessments, to usual care in populations at low risk for complications. Although the power to detect differences was limited for most outcomes, overall having fewer prenatal visits was not associated with better or worse pregnancy outcomes based on two trials. A large US trial (N= 2,328) including mostly White participants (81%) and a similarly sized UK trial (N= 2,794) where approximately one-third of participants belonged to an “ethnic minority” reported no evidence of differences in preeclampsia diagnoses (RR 0.94 [95% CI, 0.78 to 1.14] and RR 0.85 [95% CI, 0.35 to 2.04], respectively) or in maternal or perinatal health outcomes associated with a reduced visit schedule, although many of the outcomes were uncommon, which limited precision and the ability to rule out differences in serious outcomes. A small US trial (N = 81) was very underpowered for assessing differences between groups for serious health outcomes; few harms outcomes were reported. The UK trial and the small US trial assessed rates of anxiety or depression during and after pregnancy but did not find differences associated with the visit schedule. A fair-quality non-randomized study with a historical control (N = 2,441) evaluated the effect of implementing indicated instead of routine urine screening in a setting predominantly serving Hispanic/Latino people with public health insurance reported. Indicated urine screening was associated with increased risk of preterm birth compared to routine screening (RR 0.64 [95% CI, 0.45 to 0.90]), and diagnoses of hypertensive disorders of pregnancy did not differ following implementation.
There is very little evidence available to assess potential changes to clinical screening practices that could improve clinical outcomes related to hypertensive disorders of pregnancy. Only one fair-quality randomized study provided evidence on the effects of incorporating home-based blood pressure measurement to screen for hypertensive disorders of pregnancy on patient health outcomes. The included studies of reduced visit schedules provide potentially confounded tests of the effects of fewer office-based blood pressure measurements over the course of pregnancy, as a change in frequency of other tests and counseling received during visits could also influence the results. The evidence on an indicated urine screening strategy is very limited given the risks of bias inherent to historically controlled studies; reported findings may be due to factors other than the screening program. Black and American Indian/Alaska Native people, who experience the highest risks for adverse pregnancy-related health outcomes, were very underrepresented in the included studies.
Screening for hypertensive disorders of pregnancy with standard of care office-based blood pressure measurement can identify individuals requiring further surveillance and evidence-based clinical management to decrease risks for related adverse pregnancy outcomes. Research is needed to develop and strengthen clinical screening and management, possibly incorporating telehealth, home-based blood pressure measurement, and postpartum screening. Addressing troubling and persistent health inequities related to hypertensive disorders of pregnancy among specific populations in the US – especially Black and American Indian/Alaska Native people – will require interventions at multiple levels, including policies, health systems, and clinical practices.
