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


METHODS
Population-based cohort study.


METHODS
USA.


METHODS
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.


METHODS
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.
Department of Obstetrics and Gynaecology, University of British Columbia, Vancouver, BC, Canada. jhutcheon@cfri.ca
J A
JA
Hutcheon
S
S
Lisonkova
L A
LA
Magee
P
P
Von Dadelszen
H L
HL
Woo
S
S
Liu
K S
KS
Joseph
D002908:Chronic Disease; D005260:Female; D005865:Gestational Age; D006801:Humans; D006973:Hypertension / Q000401:mortality*; D007226:Infant Mortality; D007231:Infant, Newborn; D007751:Labor, Induced / Q000401:mortality*; D011247:Pregnancy; D011249:Pregnancy Complications, Cardiovascular / Q000401:mortality*; D012307:Risk Factors; D050497:Stillbirth / Q000453:epidemiology*; D013997:Time Factors; D014481:United States / Q000453:epidemiology