Abstract: We included six trials, with a total of 748 women in this review. All trials included women in whom there was no overriding indication for immediate delivery in the fetal or maternal interest. Half of the trials were at low risk of bias for methods of randomisation and allocation concealment; and four trials were at low risk for selective reporting. For most other domains, risk of bias was unclear. There were insufficient data for reliable conclusions about the comparative effects on most outcomes for the mother. Two studies reported on maternal deaths; neither study reported any deaths (two studies; 320 women; low-quality evidence). It was uncertain whether interventionist care reduced eclampsia (risk ratio (RR) 0.98, 95% confidence interval (CI) 0.06 to 15.58; two studies; 359 women) or pulmonary oedema (RR 0.45, 95% CI 0.07 to 3.00; two studies; 415 women), because the quality of the evidence for these outcomes was very low. Evidence from two studies suggested little or no clear difference between the interventionist and expectant care groups for HELLP (haemolysis, elevated liver enzymes, and low platelets) syndrome (RR 1.09, 95% CI 0.62 to 1.91; two studies; 359 women; low-quality evidence). No study reported on stroke. With the addition of data from two studies for this update, there was now evidence to suggest that interventionist care probably made little or no difference to the incidence of caesarean section (average RR 1.01, 95% CI 0.91 to 1.12; six studies; 745 women; Heterogeneity: Tau² = 0.01; I² = 63%). For the baby, there was insufficient evidence to draw reliable conclusions about the effects on perinatal deaths (RR 1.11, 95% CI 0.62 to 1.99; three studies; 343 women; low-quality evidence). Babies whose mothers had been allocated to the interventionist group had more intraventricular haemorrhage (RR 1.94, 95% CI 1.15 to 3.29; two studies; 537 women; moderate-quality evidence), more respiratory distress caused by hyaline membrane disease (RR 2.30, 95% CI 1.39 to 3.81; two studies; 133 women), required more ventilation (RR 1.50, 95% CI 1.11 to 2.02; two studies; 300 women), and were more likely to have a lower gestation at birth (mean difference (MD) -9.91 days, 95% CI -16.37 to -3.45 days; four studies; 425 women; Heterogeneity: Tau² = 31.74; I² = 76%). However, babies whose mothers had been allocated to the interventionist group were no more likely to be admitted to neonatal intensive care (average RR 1.19, 95% CI 0.89 to 1.60; three studies; 400 infants; Heterogeneity: Tau² = 0.05; I² = 84%). Babies born to mothers in the interventionist groups were more likely to have a longer stay in the neonatal intensive care unit (MD 7.38 days, 95% CI -0.45 to 15.20 days; three studies; 400 women; Heterogeneity: Tau² = 40.93, I² = 85%) and were less likely to be small-for-gestational age (RR 0.38, 95% CI 0.24 to 0.61; three studies; 400 women). There were no clear differences between the two strategies for any other outcomes. This review suggested that an expectant approach to the management of women with severe early onset pre-eclampsia may be associated with decreased morbidity for the baby. However, this evidence was based on data from only six trials. Further large, high-quality trials are needed to confirm or refute these findings, and establish if this approach is safe for the mother.

Plain-language summary: We searched for evidence in November 2017 and identified six randomised trials. This review included six trials that randomly assigned women to a policy of interventionist management or expectant management when presenting with severe pre-eclampsia before 34 weeks of pregnancy. A total of 748 women were included in these six trials. Babies born to women allocated to an interventionist approach were probably more likely to experience adverse effects such as bleeding in the brain (intraventricular haemorrhage). They may also have been more likely to require ventilation, have a longer stay in the neonatal unit, have a lower gestation at birth in days, and weigh less at birth than those babies born to women allocated to an expectant management approach. There was insufficient evidence for reliable conclusions about the effects on perinatal deaths. Babies whose mothers had been allocated to the interventionist group were no more likely to be admitted to neonatal intensive care. There were no maternal deaths in the two studies that reported this outcome. The evidence was very low-quality for the outcome of fits or convulsions (eclampsia), or of fluid in the lungs (pulmonary oedema), and so it was uncertain whether interventionist care made any clear difference to the mothers' health. Evidence from two studies suggested little or no clear difference between the interventionist and expectant care groups for a severe form of pre-eclampsia, which affects the liver and blood clotting, called HELLP syndrome, which stands for haemolysis (breakdown of red blood cells), elevated liver enzymes (a sign of liver damage), and low platelets (platelets help the blood to clot). None of the studies reported on the incidence of stroke in the mother. With the addition of data from two studies for this update, there was now evidence to suggest that interventionist care probably made little or no difference to the caesarean section rate. In the absence of an over-riding maternal or fetal indication for immediate delivery, delay may be more beneficial for the baby. However, there were insufficient data to enable us to draw reliable conclusions about the comparative effects on most outcomes for the mother, and hence the maternal safety of an expectant approach. This evidence was based on data from only six trials. Further large trials with long-term follow-up of the children are needed to confirm or refute whether expectant care is better than early delivery for women who suffer from severe pre-eclampsia before 34 weeks of pregnancy.