Optimal timing of delivery for pregnancies with pre-existing hypertension

Chronic high blood pressure in pregnant women is associated with serious maternal and fetal complications such as poor growth, early separation of the placenta, and stillbirth. Consequently, the recommendation has been made that all women with chronic high blood pressure be considered candidates for induced delivery to reduce the risk of complications that may occur with allowing pregnancies to continue to later gestational ages. However, the optimal gestational age at which the infants should be delivered is currently unknown: delivering too early may increase the risk of respiratory complications for the infant at birth, while delaying the induction of delivery increases the risk of stillbirth. Dr. Hutcheon’s research centres on the development of a methodology to help determine the optimal gestational week for delivery. Data on maternal characteristics and pregnancy outcomes obtained from the US population birth registry as well as Canadian Birth Registries will be reviewed with a focus on the occurrence of either a serious birth complication for the newborn (such as seizures or need for prolonged assisted ventilation), or stillbirth. Among women with pre-existing high blood pressure, the risks of a poor pregnancy outcome will be calculated for each week of gestation between 36 and 42 weeks of pregnancy. Statistical models will be used to determine the gestational age range for birth during which risks to the infants are lowest. These analyses will then be repeated to determine the timing of delivery that minimizes risks of serious complications for the mother. With childbearing at older maternal ages increasing in Canada, the number of pregnancies complicated by high blood pressure is expected to increase. The results of Dr. Hutcheon’s project will help provide guidance to physicians as to the best time to deliver pregnancies complicated by pre-existing high blood pressure and, as a result, help minimise the number of adverse pregnancy outcomes in the Canadian population.