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

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). 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. 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,  < .00001) and lowered BW (WMD -13.71, 95% CI -83.28 to 55.87,  = .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). 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.