Effect of chronic hypertension on assisted pregnancy outcomes: a population-based study in Ontario, Canada

Abstract

Objective: To evaluate maternal and neonatal outcomes in women with chronic hypertension who conceive using assisted reproductive technologies (ART).

Design: Population-based retrospective cohort study.

Setting: Obstetric hospitals.

Patient(s): Singleton pregnancies of at least 20 weeks' gestational age to women 18 years and older who delivered a live or stillborn infant between April 1, 2006, and March 31, 2012, categorized as exposed based on a diagnosis of chronic hypertension in the mother predating the index pregnancy.

Intervention(s): Medically assisted pregnancy including in vitro fertilization/intracytoplasmic sperm injection (IVF-ICSI), intrauterine insemination, and ovulation induction.

Primary outcome: placental-mediated complications of pregnancy (preeclampsia/eclampsia, stillbirth, fetal growth restriction/low birthweight [<10th percentile], or clinically significant placental abruption); secondary outcomes: cesarean delivery (planned/unplanned), prematurity (<37 or <32 weeks), and neonatal death.

Result(s): Our cohort included 807,765 singleton pregnancies. We used log binomial regression to compute the adjusted relative risks of the various outcomes in women with hypertension as compared with healthy women in ART and unassisted pregnancies. When we tested an interaction term between hypertension and ART in multivariate models, women with ART pregnancies were at higher risk of placental-mediated complications than were those with unassisted pregnancies (adjusted risk ratio 1.48; 95% confidence interval, 1.35, 1.56). The risk was even greater in hypertensive women who used ART (adjusted risk ratio 6.77; 95% confidence interval, 4.72, 9.72). Our findings persisted when assessing IVF only and when evaluating nulliparas.

Conclusion(s): Hypertension is more frequent in ART-treated women. Hypertension increases the risk of placental complications, which appear to be compounded in ART versus unassisted pregnancies.

Keywords: ART; hypertension; placental complications of pregnancy.