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BJOG. 2011 Jan;118(1):49-54. doi: 10.1111/j.1471-0528.2010.02754.x. Epub 2010 Nov 4.

Optimal timing of delivery in pregnancies with pre-existing hypertension.

Author information

1
Department of Obstetrics and Gynaecology, University of British Columbia, Vancouver, BC, Canada. jhutcheon@cfri.ca

Abstract

OBJECTIVE:

To determine the optimal timing of delivery in pregnancies with pre-existing (chronic) hypertension by quantifying the gestational age-specific risks of stillbirth associated with ongoing pregnancy and the gestational age-specific risks of neonatal mortality or serious neonatal morbidity following the induction of labour.

DESIGN:

Population-based cohort study.

SETTING:

USA.

POPULATION:

A total of 171 669 singleton births to women with pre-existing hypertension between 1995 and 2005. Pregnancies additionally complicated by diabetes mellitus, cardiac, pulmonary or renal disease were excluded.

METHODS:

The week-specific risks of stillbirth between 36 and 41 completed weeks of gestation were contrasted with the week-specific risks of neonatal mortality or serious neonatal morbidity among births following induction of labour in women with pre-existing hypertension.

MAIN OUTCOME MEASURES:

Stillbirth, neonatal mortality or serious neonatal morbidity (defined as a composite outcome which included any of the following: neonatal seizures, severe respiratory morbidity or 5-minute Apgar score ≤3).

RESULTS:

The risk of stillbirth in women with pre-existing hypertension remained stable at 1.0-1.1 per 1000 ongoing pregnancies until 38 weeks, before rising steadily to 3.5 per 1000 [95% confidence interval (CI): 2.4, 5.0] at 41 weeks. The risk of serious neonatal morbidity/neonatal mortality decreased sharply between 36 and 38 weeks from 137 [95% CI: 127, 146] to 26 [95% CI: 24, 29] per 1000 induced births, before stabilising beyond 39 weeks.

CONCLUSIONS:

Among women with otherwise uncomplicated pre-existing hypertension, delivery at 38 or 39 weeks appears to provide the optimal trade-off between the risk of adverse fetal and adverse neonatal outcomes.

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