Preeclampsia and neonatal outcomes in pregnancies with maternal congenital heart disease: A nationwide cohort study from Norway

Abstract Introduction The prevalence of congenital heart disease (CHD) among women of reproductive age is rising. We aimed to investigate the risk of preeclampsia and adverse neonatal outcomes in pregnancies of mothers with CHD compared to pregnancies of mothers without heart disease. Material and Methods In a nationwide cohort of pregnancies in Norway 1994–2014, we retrieved information on maternal heart disease, the course of pregnancy, and neonatal outcomes from national registries. Comparing pregnancies with maternal CHD to pregnancies without maternal heart disease, we used Cox regression to estimate the adjusted hazard ratio (aHR) for preeclampsia and log‐binomial regression to estimate the adjusted risk ratio (aRR) for adverse neonatal outcomes. The estimates were adjusted for maternal age and year of childbirth and presented with 95% confidence intervals (CIs). Results Among 1 218 452 pregnancies, 2425 had mild maternal CHD, and 603 had moderate/severe CHD. Compared to pregnancies without maternal heart disease, the risk of preeclampsia was increased in pregnancies with mild and moderate/severe maternal CHD (aHR1.37, 95% CI 1.14–1.65 and aHR 1.62, 95% CI 1.13–2.32). The risk of preterm birth was increased in pregnancies with mild maternal CHD (aRR 1.33, 95% CI 1.15–1.54) and further increased with moderate/severe CHD (aRR 2.49, 95% CI 2.03–3.07). Maternal CHD was associated with elevated risks of both spontaneous and iatrogenic preterm birth. The risk of infants small‐for‐gestational‐age was slightly increased with mild maternal CHD (aRR 1.12, 95% CI 1.00–1.26) and increased with moderate/severe CHD (aRR 1.63, 95% CI 1.36–1.95). The prevalence of stillbirth was 3.9 per 1000 pregnancies without maternal heart disease, 5.6 per 1000 with mild maternal CHD, and 6.8 per 1000 with moderate/severe maternal CHD. Still, there were too few cases to report a significant difference. There were no maternal deaths in women with CHD. Conclusions Moderate/severe maternal CHD in pregnancy was associated with increased risks of preeclampsia, preterm birth, and infants small‐for‐gestational‐age. Mild maternal CHD was associated with less increased risks. For women with moderate/severe CHD, their risk of preeclampsia and adverse neonatal outcomes should be evaluated together with their cardiac risk in pregnancy, and follow‐up in pregnancy should be ascertained.