The association between first trimester blood pressure, blood pressure trajectory, mid-pregnancy blood pressure drop and maternal and fetal outcomes: A systematic review and meta-analysis

Background: Hypertensive disorders of pregnancy occur in 5–10 % of pregnancies and are associated with an increased risk of adverse perinatal outcomes. Objectives: This review investigates the association between first trimester blood pressure (BP), mid-pregnancy BP drop, and BP-trajectories during pregnancy and adverse perinatal outcomes, exploring the fit of prediction and prevention. Search strategy: Observational studies published before September 2023, reporting on desired determinants of BP and outcomes (preeclampsia (PE), severe hypertension, small for gestational age (SGA), fetal growth restriction (FGR)) were identified in MEDLINE, Embase and Cochrane. Data collection and analysis: Data were collected in Excel. Results were analysed per BP-determinant. Meta analysis was performed for first trimester BP. Main results: Ten studies met selection criteria. A great variety of cut-off values were used for BP categorization. Pooled analysis of 6 studies showed that women with borderline or hypertensive first trimester BP had a higher risk of PE compared to normotensive BP, OR 3.23 (95 % CI 1.99–5.26) and 7.86 (95 % CI 1.28–48.31), respectively. Additionally, first trimester hypertension correlated with a higher risk of SGA neonate (pooled OR of 1.87 (95 % CI 1.17–2.99)) compared to normotension or borderline hypertension. Throughout pregnancy, prehypertension, hypertension, elevated and high stable trajectories increased PE risk. High-stable trajectory increased SGA neonate risk. Conclusions: The findings suggest that women with borderline and hypertensive BP in the first trimester are at increased risk for PE and SGA. However, standardization of cut-off values and BP measurement is necessary to estimate outcome risks more accurately.