Temperature-dependent variation in gestational diabetes diagnosis and its impact on macrosomia and LGA infant

Although the influence of temperature on gestational diabetes mellitus (GDM) has been extensively researched, it remains debatable whether this influence stems from a temporary alteration in blood glucose levels due to temperature adaptation or represents a genuine effect on the intrauterine environment. This study aimed to explore the impact of ambient temperature on the diagnosis accuracy of GDM by analyzing pregnancy outcomes among GDM pregnancies diagnosed at different temperatures. This cohort study included 65,908 singleton pregnant women who delivered at the Guangdong Women and Children Hospital between January 2015 and June 2022. Participants were categorized based on the 24-hour and morning (8:00–11:00 AM) average ambient temperatures recorded on their oral glucose tolerance test (OGTT) day, using the 5th and 95th percentiles as cut-offs, defining low, moderate, and high temperature groups, respectively. We compared the prevalence of GDM and the subsequent risk of macrosomia or large-for-gestational-age (LGA) infants across these groups. Risk ratios (RRs) for macrosomia and LGA infants in GDM pregnancies diagnosed at low or moderate temperatures, relative to high temperatures were quantified using modified Poisson regression. Among the 65,908 pregnant women, the prevalence of GDM varied by ambient temperature. When stratified by the 24-hour average temperature, the prevalence was highest in the high-temperature group (20.0%), followed by the moderate- (18.2%) and low-temperature (16.4%) groups. A similar gradient was observed for the morning average temperature, with prevalence rates of 20.2%, 18.3%, and 15.8% in the high-, moderate-, and low-temperature groups, respectively. Compared with GDM pregnancies diagnosed at high 24-hour average temperatures, those diagnosed at low temperatures were more likely to develop an LGA infant (10.2% vs. 6.3%; adjusted RR: 1.48, 95% CI: 1.01, 2.18) and macrosomia (4.6% vs. 2.2%; adjusted RR: 1.90, 95% CI: 1.01, 3.59). A consistent pattern was observed when using the morning average temperature for stratification. While GDM prevalence rose with increasing ambient temperature on the OGTT day, the rates of subsequent LGA infants and macrosomia among GDM pregnancies fell. The divergent patterns between diagnosis rates and neonatal outcomes suggest that temperature may influence glycemic measurements and diagnostic classification.