The 2017 American College of Cardiology and American Heart Association blood pressure categories in the second half of pregnancy—a systematic review of their association with adverse pregnancy outcomes

OBJECTIVE: A relationship between the 2017 American College of Cardiology and American Heart Association blood pressure thresholds and adverse pregnancy outcomes has been reported, but few studies have explored the diagnostic test properties of these cutoffs when used within pregnancy. DATA SOURCES: Electronic databases were searched (2017-2021) for measurements of blood pressure in pregnancy at >20 weeks, classified according to the 2017 American College of Cardiology and American Heart Association criteria, and their relationship with pregnancy outcomes. Blood pressure was categorized as "normal" (systolic blood pressure of <120 mm Hg and diastolic blood pressure of <80 mm Hg), "elevated blood pressure" (systolic blood pressure of 120-129 mm Hg and diastolic blood pressure of <80 mm Hg), "stage 1 hypertension" (systolic blood pressure of 130-139 mm Hg and/or diastolic blood pressure of 80-89 mm Hg), and "stage 2 hypertension" (systolic blood pressure of ≥140 mm Hg and/or diastolic blood pressure of ≥90 mm Hg). STUDY ELIGIBILITY CRITERIA: Studies recording blood pressure at or above 20 weeks gestation were included. METHODS: Meta-analyses were used to investigate the strength of the association between blood pressure cutoffs and adverse outcomes, and the diagnostic test properties were calculated accounting for gestation. RESULTS: There were 12 included studies. The American College of Cardiology or American Heart Association blood pressure categories were determined from peak blood pressures at any point from 20 weeks of gestation and at specific gestational ages (20-27, 28-32, or 33-36 weeks of gestation), as available. A higher (vs normal) blood pressure category was consistently associated with adverse outcomes. The strength of association between blood pressure categories and adverse outcomes was the greatest with "stage 2 hypertension" (blood pressure of ≥140/90 mm Hg). The results were similar when peak blood pressure was reported either at any time from 20 weeks of gestation or within gestational age groups (as above). No blood pressure category was useful as a diagnostic "rule-out test" for adverse outcomes, as all negative likelihood ratios were ≥0.2. Only "stage 2 hypertension" was useful as a "rule in-test," with positive likelihood ratios of ≥5.0, for maximum blood pressure at >20 weeks of gestation for preeclampsia and blood pressure within any gestational age groups for preeclampsia, eclampsia, stroke, maternal death, and stillbirth. CONCLUSION: From 20 weeks of gestation, blood pressure thresholds of 140 mm Hg (systolic) and 90 mm Hg (diastolic) were useful in identifying women at increased risk of adverse pregnancy outcomes, irrespective of the specific gestational age at blood pressure measurement. Lowering the blood pressure threshold for abnormal blood pressure at >20 weeks of gestation would not assist clinicians in identifying women at heightened maternal or perinatal risk. No American College of Cardiology or American Heart Association blood pressure threshold can provide reassurance that women are unlikely to develop adverse outcomes.

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