To assist the CF community with better data to guide use of CFTR modulators during pregnancy and lactation, beginning in late 2021, Drs. Jain and Taylor-Cousar will lead a multi-site prospective U.S. study, funded by the CF Foundation, to evaluate Maternal and FetaL Outcomes in the ERa of ModulatorS (MAYFLOWERS, NCT04828382). This evidence concerns the gene CFTR and cystic fibrosis.