Impact of β-Blockers on the Risk of Low-Birth-Weight Infants in Women with Long QT Syndrome or Marfan Syndrome: A Single-Center Retrospective Study from 2008 to 2022 in a Tertiary Care Center.

introductionβ-Blockers are an essential treatment for cardiovascular disease, the incidence of which is rising among women of childbearing age. Several large cohort and registry studies have reported an association between β-blocker exposure in pregnancy and reduced birth weight, but most have included women with hypertension or structural heart disease. Our study's primary objective was to evaluate the impact of these medications on the birth weight of infants born to mothers with morphologically normal hearts, including women with long QT syndrome (LQTS) or Marfan syndrome (MFS). Secondary objectives were to evaluate the influence of β-blocker type on birth weight, diagnoses that fetuses were small for gestational age (SGA) or growth-restricted (FGR) during pregnancy and at birth, uterine Doppler abnormalities, and neonatal adverse effects (bradycardia and hypoglycemia), which are expected effects of in utero β-blocker exposure. MATERIALS AND

methodsThis retrospective observational single-center study compared pregnancies in patients with LQTS or MFS treated with β-blockers with those of untreated matched control patients. Pregnancies were matched for maternal age, body mass index, parity, gestational age at birth, presence of gestational or pre-existing diabetes, and smoking status.

resultsFifty-seven pregnancies of 40 mothers exposed to β-blockers were matched with 165 control pregnancies. This study's main finding was that the mean birth weight of infants whose mothers used β-blockers during pregnancy was a significant 442 grams lower (unadjusted 2890 g vs 3285 g; p < 0.001) than that of the control group. SGA/FGR during pregnancy and at birth were diagnosed significantly more often in the treated patients, and their incidence of neonatal bradycardia was higher in the exposed group. Among the uterine Doppler examinations available, no clear differences were observed between groups. Data on neonatal hypoglycemia were inconclusive because of differential screening strategies and a high proportion of missing values, particularly in the control group. DISCUSSION: To our knowledge, this is the first study specifically focusing on β-blocker use in pregnant women with LQTS or MFS and structurally normal hearts, using matched controls to minimize confounding by underlying cardiac disease. β-Blocker use-mainly nadolol and bisoprolol-was associated with significantly lower birth weight and higher rates of FGR/SGA and neonatal bradycardia. Our findings support the continuation of β-blocker therapy when clinically indicated, combined with careful fetal growth monitoring and targeted neonatal surveillance.