High Incidence of Gestational Diabetes Mellitus in Females With Cystic Fibrosis Persists in the Triple Cystic Fibrosis Transmembrane Conductance Regulator Modulator Era: Implications for Screening.

OBJECTIVE

Historically, pregnancies in females with cystic fibrosis (FwCF) were considered high risk, with a high prevalence of gestational diabetes mellitus (GDM). Widespread availability of cystic fibrosis (CF) transmembrane conductance regulator modulator has led to significantly increased pregnancy rates. This study reviewed preconception characteristics of FwCF who develop GDM to better inform FwCF and clinicians about individualized risk of GDM and contribute to the evidence base for personalized preconception counseling.

METHODS

Retrospective review of clinically collected data from FwCF who completed pregnancies between September 2020 and November 2025 as part of a quality improvement evaluation for a CF Reproductive and Maternal Health Service. Females with CF-related diabetes (CFRD) or prepregnancy dysglycemia were excluded. CF characteristics were compared according to incidence and timing of GDM diagnosis.

RESULTS

A total of 77 pregnancies were completed by 60 FwCF. A total of 19/77 (25%) FwCF with CFRD were excluded from analysis, and 1 removed due to insufficient data. A total of 27/57 (47%) pregnancies (45 FwCF) were complicated by GDM. Approximately 48% of GDM diagnoses were made at an early oral glucose tolerance test. FwCF developing GDM had a higher body mass index (GDM: 23.7 ± 0.8 kg/m2 (mean ± SEM); no GDM: 21.4 ± 0.5 kg/m2, P < .05) but no significant differences in age, spirometry, or preconception A1C. FwCF with pancreatic exocrine insufficiency were significantly more likely to develop GDM.

CONCLUSION

Despite improved CF health status, elevated GDM risk persists in FwCF relative to the general population. Recognition of value and indication for 2 oral glucose tolerance tests for GDM screening is evident as almost 50% cases were detected early. Further research into how CFRD and GDM impacts maternal/fetal outcomes in FwCF is warranted.