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INTRODUCTION: Survival and healthcare for patients with congenital heart disease have improved, and the number of pregnancies among women of childbearing age with congenital heart disease has increased. Our aim was to investigate obstetric outcomes in a large retrospective, national registry study of women with congenital heart disease compared to controls.

MATERIAL AND METHODS: The study included women over 18 years of age from the Swedish Registry of Congenital Heart Disease. Each case was matched with 10 controls from Statistics Sweden, based on the mother's birth year and birth county and all were subsequently linked to the Swedish Medical Birth Register. We included 7998 pregnancies in women with congenital heart disease and 84 799 in controls during 1973-2020.

RESULTS: The mean age at delivery for women with congenital heart disease and controls was 28.7 (±5.0) and 28.7 (±5.1) years, respectively. Women with congenital heart disease smoked less, had a shorter gestation and a higher incidence of delivery by Cesarean section compared to controls. The likelihood of Cesarean section was increased in women with congenital heart disease compared to controls: odds ratio 1.45 (95% confidence interval (CI) 1.37-1.54). Compared to controls, women with congenital heart disease had an increased likelihood of giving birth to small-for-gestational-age neonates: odds ratio 1.40 (95% CI 1.23-1.58). The association regarding small-for-gestational-age remained after adjusting for body mass index, age, smoking, comorbid diseases and preeclampsia. Women with congenital heart disease had an increased likelihood of prematurity compared to controls: odds ratio 1.47 (95% CI 1.35-1.59). The likelihood of Cesarean section, small-for-gestational-age neonates and prematurity was higher in women with severe congenital heart disease than mild/moderate congenital heart disease, both compared to controls.

CONCLUSIONS: In this large national case-control study in women with congenital heart disease, we showed an increased likelihood of giving birth prematurely by Cesarean section, and having a small-for-gestational-age neonate compared to matched controls. The likelihood seems even higher in women with severe congenital heart disease. Further research is needed to explore the underlying reasons for the high rates of Cesarean section in women with congenital heart disease.