CFTR modulators and pregnancy outcomes: Early findings from a nationwide cohort study.

Objectives: Recent therapeutic advances, mainly with the advent of CFTR modulators, have been associated with an increasing number of pregnancies in females with cystic fibrosis (fwCF). This study aimed to evaluate the safety of the use of CFTR modulators, specifically elexacaftor/tezacaftor/ivacaftor (ELX/TEZ/IVA) during pregnancy.

Methods: A nationwide cohort study was conducted using the French health insurance data warehouse (SNDS), covering nearly all singleton pregnancies ending between January 2018 and December 2023. Exposure to CFTR modulators was defined as using prescriptions through pregnancy, including one month in the preconception period. The study compared pregnancy outcomes amongst fwCF between pregnancies exposed and unexposed to CFTR modulators.

Results: Among 590 pregnancies in fwCF, 148 (24.7 %) were exposed to CFTR modulators, including 136 during first trimester. Of these, 147 (99.3 %) resulted in livebirths. The most common CFTR modulator used was ELX/TEZ/IVA, in 121 (81.8 %) pregnancies. The prevalence of major birth defects was similar between exposed and unexposed fwCF (3.38 % vs. 4.66 %; p = 0.72). The rate of small for gestational age (SGA, <10th percentile) was significantly lower in pregnancies exposed compared to unexposed (6.8 % vs. 16.1 %; p < 0.01).

Discussion: The study provides early reassurance about the safety of CFTR modulators during pregnancy, particularly in terms of teratogenicity and adverse pregnancy outcomes. While findings suggest potential benefits, such as halved rate of SGA, further research is required to confirm these outcomes and investigate long-term effects on the development of children prenatally exposed to CFTR modulators.