Prehypertension during pregnancy and risk of small for gestational age: a systematic review and meta-analysis

Objective: Emerging evidence shows that high blood pressure (BP) level even below 140/90 mmHg during pregnancy is associated with increased risk for maternal and infant complications. The meta-analysis evaluated the associations between prehypertension (BP 120-139/80-89 mmHg) during pregnancy and the risk of small for gestational age (SGA), as well as the impact of prehypertension on birth weight (BW). Methods: Databases (PubMed, Embase, and Cochrane Library) were searched for cohort studies with data on prehypertension in pregnancy and adverse obstetrical outcomes, including SGA and/or BW. The relative risks (RRs) of SGA and weighted mean differences (WMD) in BW were calculated and reported with 95% confidence intervals (95% CIs). We calculated pooled RRs using fixed- and random-effects models. Results: A total of 143,835 participants from five cohort studies were included. Prehypertension in pregnancy increased the risk of SGA (RR 1.59, 95%CI 1.44 to 1.76, p < .00001) and lowered BW (WMD -13.71, 95% CI -83.28 to 55.87, p = .70) compared with optimal BP (<120/80 mmHg). In subgroup analyses, for prehypertension in late pregnancy, the risk of SGA was significantly higher than for optimal BP (RR 1.60, 95% CI 1.44 to 1.78). Conclusion: BP within the range of 120-139/80-89 mmHg during pregnancy, as previously defined as prehypertension, particularly in late pregnancy, was associated with a 59% increase in the risk of having an SGA birth.