Abstract: We included five studies (involving 1819 women) in this review. There was a lower risk of composite maternal mortality and severe morbidity for women randomised to receive planned early delivery (risk ratio (RR) 0.69, 95% confidence interval (CI) 0.57 to 0.83, two studies, 1459 women (evidence graded high)). There were no clear differences between subgroups based on our subgroup analysis by gestational age, gestational week or condition. Planned early delivery was associated with lower risk of HELLP syndrome (RR 0.40, 95% CI 0.17 to 0.93, 1628 women; three studies) and severe renal impairment (RR 0.36, 95% CI 0.14 to 0.92, 100 women, one study). There was not enough information to draw any conclusions about the effects on composite infant mortality and severe morbidity. We observed a high level of heterogeneity between the two studies in this analysis (two studies, 1459 infants, I2 = 87%, Tau2 = 0.98), so we did not pool data in meta-analysis. There were no clear differences between subgroups based on our subgroup analysis by gestational age, gestational week or condition. Planned early delivery was associated with higher levels of respiratory distress syndrome (RR 2.24, 95% CI 1.20 to 4.18, three studies, 1511 infants), and NICU admission (RR 1.65, 95% CI 1.13 to 2.40, four studies, 1585 infants). There was no clear difference between groups for caesarean section (RR 0.91, 95% CI 0.78 to 1.07, 1728 women, four studies, evidence graded moderate), or in the duration of hospital stay for the mother after delivery of the baby (mean difference (MD) -0.16 days, 95% CI -0.46 to 0.15, two studies, 925 women, evidence graded moderate) or for the baby (MD -0.20 days, 95% CI -0.57 to 0.17, one study, 756 infants, evidence graded moderate). Two fairly large, well-designed trials with overall low risk of bias contributed the majority of the evidence. Other studies were at low or unclear risk of bias. No studies attempted to blind participants or clinicians to group allocation, potentially introducing bias as women and staff would have been aware of the intervention and this may have affected aspects of care and decision-making. The level of evidence was graded high (composite maternal mortality and morbidity), moderate (caesarean section, duration of hospital stay after delivery for mother, and duration of hospital stay after delivery for baby) or low (composite infant mortality and morbidity). Where the evidence was downgraded, it was mostly because the confidence intervals were wide, crossing both the line of no effect and appreciable benefit or harm. For women suffering from hypertensive disorders of pregnancy after 34 weeks, planned early delivery is associated with less composite maternal morbidity and mortality. There is no clear difference in the composite outcome of infant mortality and severe morbidity; however, this is based on limited data (from two trials) assessing all hypertensive disorders as one group. Further studies are needed to look at the different types of hypertensive diseases and the optimal timing of delivery for these conditions. These studies should also include infant and maternal morbidity and mortality outcomes, caesarean section, duration of hospital stay after delivery for mother and duration of hospital stay after delivery for baby. An individual patient meta-analysis on the data currently available would provide further information on the outcomes of the different types of hypertensive disease encountered in pregnancy.

Plain-language summary: We searched for evidence on 12 January 2016 and found five randomised studies, involving 1819 women. Two of the studies were large, high-quality studies, in women with gestational hypertension, mild pre-eclampsia or deteriorating existing hypertension at 34 to 37 weeks (704 women) or with gestational hypertension or mild pre-eclampsia at 36 to 41 weeks (756 women). Fewer women who received planned early delivery experienced severe adverse outcomes (1459 women, high-quality evidence). There was not enough information to draw any conclusions about the effects on the number of babies born with poor health, with a high level of variability between the two studies (1459 infants, low-quality evidence). There was no clear difference between planned early delivery and delayed delivery for the number of caesarean sections (four studies, 1728 women, moderate-quality evidence), or the duration of the mother’s hospital stay after the birth of the baby (two studies, 925 women, moderate-quality evidence) (or for the baby (one study, 756 infants, moderate-quality evidence)). More babies who were delivered early had breathing problems (respiratory distress syndrome, three studies, 1511 infants), or were admitted to the neonatal unit (four studies, 1585 infants). Fewer women who delivered early developed HELLP syndrome (three studies, 1628 women) or severe kidney problems (one study, 100 women). Two studies compared women who had labour induced at 34 to 36 weeks and at 34 to 37 weeks with a comparison group who were monitored until 37 weeks, when induction was begun if labour had not started spontaneously. Three studies compared induction of labour at term or closer to term, at 37 completed weeks and at 36 to 41 weeks, with women who were monitored until 41 weeks when induction was begun if labour had not started spontaneously. Other inclusion and exclusion criteria also differed between the five studies. No studies attempted to blind the women or their clinicians to which group they were in. Women and staff were aware of the intervention and this may have affected aspects of care and decision-making. Most of the evidence was of moderate quality, so we can be moderately certain about the findings. Overall, if a woman’s baby was delivered immediately after 34 weeks, there was less risk of a complication for the mother and no clear difference in the overall rate of complications for the baby, but information was limited. These findings are applicable to general obstetric practice when high blood pressure disorders during pregnancy are considered together. Further studies are needed to look at the different types of hypertensive disorders individually.