Hypertensive disorders of pregnancy and stillbirth in North Carolina, 1988 to 1991.

BACKGROUND: The objectives of this study were (i) to assess the effect of hypertensive disorders of pregnancy on the risk of stillbirth, and (ii) to characterize the relationship between hypertension and stillbirth separately by gravidity, race, 'explained' versus 'unexplained' causes of stillbirth, and antepartum versus intrapartum stillbirths.
METHODS: The study was based on a retrospective cohort of approximately 400,000 pregnancies identified through the birth and fetal death certificates in North Carolina, USA, between 1988 and 1991. Multivariable polytomous logistic regression was used to generate odds ratios comparing stillbirth risk in hypertensive compared to non-hypertensive mothers, adjusted for potential confounders.
RESULTS: The risk of chronic hypertension was 7.6 per 1000 pregnancies, while pregnancy-induced hypertension (PIH) and eclampsia were reported in 36.6 and 6.0 per 1000 pregnancies, respectively. Pregnancies among chronic hypertensives were more likely to result in losses after 28 weeks gestation (RR = 3.29, 95% CI: 2.43-4.43), while the risk ratio was 2.16 (95% CI: 1.45-3.22) for losses prior to 28 weeks' gestation. Pregnancies to patients with PIH were at 1.42 (95% CI: 1.15-1.79) times greater risk of terminating in late stillbirth, while the risk ratio for eclampsia was 2.23 (95% CI: 1.51-3.30). The risk ratio for 'explained' antepartum stillbirth was higher than intrapartum stillbirth for all of the hypertensive diseases.
CONCLUSIONS: Hypertensive disorders were found to have a strong adverse impact on stillbirth suggesting that early diagnosis of hypertension during pregnancy and adequate medical intervention may help reduce the risk of stillbirth.