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Oral Concurrent Session 2 - Diabetes

Oral Concurrent Sessions

Oral Concurrent Session 2 - Diabetes

(27) Timing of Metformin Initiation for Type 2 Diabetes in Pregnancy and Perinatal Outcomes

Wednesday, February 11, 2026

3:00 PM - 3:15 PM

Location: Summit 211 - 214

Submitting Author and Presenting Author(s)

Claire E. Jensen, MD, MSCR (she/her/hers)

Maternal Fetal Medicine Fellow
University of North Carolina at Chapel Hill
Durham, North Carolina, United States

Coauthor(s)

Kim Boggess, MD

Professor
University of North Carolina at Chapel Hill
Chapel Hill, North Carolina, United States
Kjersti M. Aagaard, MD, MSCI, PhD

Medical Director, HCA Healthcare and HCA Research Institute
HCA
Houston, Texas, United States

Objective:
Metformin is a first-line therapy for T2DM outside of pregnancy, which is often continued post-conception. In pregnancy, it is an acceptable alternative to insulin, though it is unclear how timing of initiation affects fetal safety and maternal efficacy. While metformin use reduces LGA risk, we have demonstrated this occurs via loss of neonatal fat-free mass (FFM, i.e., muscle accretion) rather than reduced adiposity. We aimed to evaluate the association between timing of metformin initiation and neonatal FFM.

Study Design:
Secondary analysis of MOMPOD RCT of metformin 1000mg BID vs. placebo in singleton pregnancies at 11-23 weeks with insulin-treated early diabetes or pre-existing T2DM. Metformin exposure was categorized as: (1) never, (2) early (preconception through randomization only), (3) continuous (preconception through delivery), and (4) late (randomization through delivery). The primary outcome was neonatal FFM, estimated from skinfold anthropometry. Secondary outcomes included composite neonatal morbidity, birthweight, SGA, LGA, maternal gestational weight gain, intrapartum IV insulin, and gestational age at delivery.

Results:
776 participants (never: 216, early: 175, continuous: 162, late: 223) were included. Mean gestational age for late exposure was 17.2 ± 3.7 wks. (Table 1). Adjusted analyses showed late exposure was associated with lower FFM compared to never exposure (-93.1g, p=0.045). In a planned pairwise comparison, late and continuous exposure were each associated with lower FFM compared to early exposure (late: -130g, p =0.01; continuous: -114g, p=0.03). Secondary outcomes did not differ by timing of metformin exposure, except for birthweight differences attributable to FFM in sensitivity analyses (Table 2).

Conclusion:
Late metformin exposure was associated with lower neonatal FFM, and restricting exposure windows shows no evidence of improved maternal or neonatal outcomes. Timing of metformin initiation appears to influence fetal lean mass development, with critical exposure windows during key periods of rapid muscle accretion in latter gestation.