Pregnancy-induced hypertension and neonatal outcomes: a systematic review and meta-analysis

OBJECTIVE: Pregnancy-induced hypertension (PIH) is associated with preterm delivery but its independent impact on neonatal outcomes remains unclear. We sought to systematically review and meta-analyze clinical outcomes of preterm infants <37 weeks' gestation born to mothers with and without PIH. STUDY DESIGN: Medline, Embase, PsychINFO and CINAHL were searched from January 2000 to October 2016. Studies with low-moderate risk of bias reporting neonatal outcomes based on PIH as primary exposure variable were included. Data were extracted independently by two co-authors. RESULTS: PIH was associated with lower mortality (3 studies; adjusted odds ratio (aOR) 0.65; 95% confidence interval (CI) 0.54 to 0.79), lower severe retinopathy of prematurity (ROP) (2 studies; aOR 0.83; 0.72 to 0.96) and lower severe brain injury (2 studies; unadjusted OR (uOR) 0.57; 0.49 to 0.66). No association between PIH and short-term respiratory outcomes, bronchopulmonary dysplasia (BPD) or necrotizing enterocolitis (NEC) was identified. In subgroup analysis among infants <29 weeks' gestation, BPD odds were higher (3 studies; aOR 1.15; 1.06 to 1.26), whereas mortality lower (2 studies; aOR 0.73; 0.69 to 0.77). In subgroup analysis limited to severe PIH, odds of mortality (3 studies; uOR 2.36; 1.07 to 5.22) and invasive ventilation (3 studies; uOR 3.26; 1.11 to 9.61) were higher. In subgroup analysis limited to preeclampsia, odds of BPD (3 studies; uOR 1.21; 95% CI: 1.03 to 1.43) and NEC were higher (3 studies; uOR 2.79; 95% CI: 1.57 to 4.96). CONCLUSION: PIH was associated with reduced odds of mortality and ROP (all infants), but higher odds for BPD (o29 weeks' gestation). The paradoxical reduction in mortality may be due to survival bias and deserves further exploration in future studies.