Planned early birth for pregnant women with high blood pressure cuts maternal complications by nearly half and reduces the risk of stillbirth, without increasing the likelihood of caesarean section.
Hypertensive disorders of pregnancy, which include pre-eclampsia, gestational hypertension, and chronic hypertension, are the second leading cause of maternal death globally. For women with pre-eclampsia, early birth remains the only definitive treatment, as the condition is driven by the placenta and will only resolve once it is delivered.
The Cochrane review, led by King's College London, pooled data from six randomized controlled trials involving 3,491 women, comparing planned early delivery after 34 weeks to watchful waiting. The trials included women with one or more types of hypertensive disorder and took place across a range of settings, including the Netherlands, UK, US, India, and Zambia.
The findings show high-certainty evidence that serious maternal complications were nearly halved in women who had a planned early birth compared to those managed with watchful waiting.
Planned early birth also likely reduces the risk of stillbirth by approximately 75%, though this should be interpreted with caution. The finding is based on moderate-certainty evidence, and the reduction was driven by a single trial conducted in India and Zambia, where stillbirth rates are higher. There were no stillbirths recorded in the high-income country trials. Reassuringly, planned early birth also likely results in no difference in neonatal unit admission, though this finding is also based on moderate-certainty evidence.
Importantly, the maternal benefit held across both high- and low-income settings, suggesting that early birth reduces complications even when women are already receiving appropriate monitoring and care.
"These findings give clinicians and women clearer guidance about the timing of birth when high blood pressure develops in pregnancy," said Prof Catherine Cluver, senior author of the review and researcher at Stellenbosch University and Tygerberg Hospital. "For women with pre-eclampsia in particular, the evidence supports offering planned early birth from 34 weeks, and no later than 37 weeks."
"A common misconception is that by waiting longer, mum and baby are gaining more time, but often what you are doing is just delaying an inevitable emergency birth, when both may be in a worse condition"
Dr Alice Beardmore-Gray, lead author of the review and Obstetrician at King's College London
The authors added that in two of the trials included, over half the women allocated to watchful waiting ended up needing emergency birth before 37 weeks, typically just three to five days later than women allocated to planned early birth, and often more experiencing more complications.
"A common misconception is that by waiting longer, mum and baby are gaining more time, but often what you are doing is just delaying an inevitable emergency birth, when both may be in a worse condition," explained Dr Beardmore-Gray.
The review found high-certainty evidence of no increased risk of caesarean section associated with planned early birth. This is a finding the authors consider particularly important for clinical counselling and women's decision-making.
"That is the first question anyone asks when you offer them an early induction: won't it increase my risk of a C-section?" said Dr Beardmore-Gray. "Being able to clearly answer no is a really important piece of information to give women when counselling them about the timing of their birth."
The authors advise that the timing of birth should take into account the woman's preferences and the severity of her condition. These findings are consistent with and reinforce current international guidelines, which recommend that all women with pre-eclampsia should be offered planned early birth no later than 37 weeks. Women with gestational hypertension or chronic hypertension without severe features may choose to continue with careful monitoring, with planned early birth considered from 39 weeks onwards.
Further research is needed on longer-term outcomes for infants born late preterm and on the long-term cardiovascular health of mothers affected by hypertensive disorders of pregnancy.
