Impact of pregnancy on the natural history of women with hypertrophic cardiomyopathy

Aims: Whether pregnancy is a modifier of the long-term course and outcome of women with hypertrophic cardiomyopathy (HCM) is unknown. We assessed the association of pregnancy with long-term outcomes in HCM women. Methods and results: Retrospective evaluation of women with HCM from 1970 to 2021. Only women with pregnancy-related information (pregnancy present or absent) and a follow-up period lasting ≥1 year were included. The peri-partum period was defined as -1 to 6 months after delivery. The primary endpoint was a composite for major adverse cardiovascular events [MACE: cardiovascular death, sudden cardiac death, appropriate defibrillator shock and heart failure (HF) progression]. Overall, 379 (58%) women were included. There were 432 pregnancies in 242 (63%) patients. In 29 (7.6%) cases, pregnancies (n = 39) occurred after HCM diagnosis. Among these, three carrying likely pathogenic sarcomeric variants suffered MACEs in the peri-partum period. At 10 ± 9 years of follow-up, age at diagnosis [hazard ratio (HR) 1.034, 95% confidence interval (CI) 1.018-1.050, P < 0.001] and New York Heart Association (NYHA) class (II vs. I: HR 1.944, 95% CI 0.896-4.218; III vs. I: HR 5.291, 95% CI 2.392-11.705, P < 0.001) were associated with MACE. Conversely, pregnancy was associated with reduced risk (HR 0.605; 95% CI 0.380-0.963, P = 0.034). Among women with pregnancy, multiple occurrences did not modify risk. Conclusions: Pregnancy is not a modifier of long-term outcome in women with HCM and mostly occurs before a cardiac diagnosis. Most patients tolerate pregnancy well and do not show a survival disadvantage compared to women without. Pregnancy should not be discouraged, except in the presence of severe HF symptoms or high-risk features.