Background: Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiomyopathy, affecting approximately 1:500 individuals in the general population. Due to improved survival and broader recognition of milder phenotypes, an increasing number of women with HCM reach reproductive age. Although the estimated prevalence of HCM in pregnancy is <1:1000, contemporary registries report preterm delivery rates ranging from 17% to 26%, suggesting that prematurity remains a frequent complication. However, determinants of preterm labor in HCM are not fully elucidated.

Methods: We conducted a single-center ambispective cohort study including 114 pregnancies in women with confirmed HCM managed between 2011 and 2025. Obstructive (n=76) and non-obstructive (n=38) phenotypes were analyzed. Preterm labor was defined as delivery <37 weeks. Clinical status (NYHA class), arrhythmias, beta-blocker therapy, and echocardiographic parameters (LV ejection fraction, left atrial size, LV outflow tract [LVOT] gradient) were evaluated during the second and third trimesters and at follow-up. Between-group comparisons were performed using χ²/Fisher’s exact test or Mann–Whitney U test as appropriate.

Results: Preterm delivery occurred in 26 of 114 pregnancies (22.8%). The incidence was significantly higher in women with obstructive HCM compared with non-obstructive phenotype (36.8% vs 15.8%, p=0.036). Patients with preterm labor more frequently had NYHA class ≥II in the third trimester (42% vs 18%, p=0.021) and demonstrated greater transient increases in LVOT gradient and left atrial size during late pregnancy (p<0.05 for within-group comparison). Ventricular arrhythmias were more prevalent in the preterm group (23% vs 9%, p=0.048).

Beta-blocker therapy was more common among women delivering preterm (69% vs 41%, p=0.018) and was associated with lower median neonatal birth weight (2660 g vs 3040 g, p=0.0069), without differences in neonatal mortality. At follow-up, LV ejection fraction and LVOT gradient returned to baseline values in the majority of patients, and no significant increase in long-term major adverse cardiovascular events was observed in women with prior preterm delivery.

Conclusions: Preterm labor in HCM occurs in approximately one in five pregnancies and is independently associated with obstructive physiology, third-trimester symptom burden, and arrhythmic events. Despite higher prematurity rates in obstructive HCM, gestation was not linked to adverse long-term cardiac remodeling or progression. Careful trimester-based risk stratification may help identify women at risk for preterm delivery.

To be Updated