Association of diagnostic oral glucose tolerance test values with neonatal hypoglycemia in diet-controlled gestational diabetes mellitus: a retrospective cohort study

BACKGROUND: Whether diagnostic oral glucose tolerance test (OGTT) values are associated with neonatal hypoglycemia (NH) in women with diet-controlled gestational diabetes mellitus (GDM) remains uncertain. We aimed to evaluate the associations of diagnostic OGTT values with neonatal glycemic outcomes and to identify other determinants of NH in this population. METHODS: In this retrospective cohort study, 2,051 singleton pregnancies with diet-controlled GDM were included from a maternal and child health center in Liaocheng, China, between January 2019 and August 2023. Diagnostic fasting blood glucose (FBG), 1-hour post-glucose (1hPG), and 2-hour post-glucose (2hPG) values from the 75-g OGTT were analyzed. Restricted cubic spline (RCS)-based linear and logistic regression models were used to assess possible non-linear associations with neonatal 1-h postnatal blood glucose and NH after adjustments. RESULTS: NH occurred in 12.0% of neonates (247/2,051). After multivariable adjustment, neither standard regression nor RCS analyses showed significant overall or non-linear associations between diagnostic OGTT values and NH or neonatal 1-h postnatal blood glucose (all P > 0.05). Gestational age at delivery was independently protective, with each additional week associated with a lower risk of NH (aOR = 0.62, 95% CI 0.48-0.80). Cesarean delivery was associated with higher odds of NH than vaginal delivery (aOR = 2.24, 95% CI 1.62-3.10). CONCLUSIONS: In diet-controlled GDM pregnancies, diagnostic OGTT values were not independently associated with NH or neonatal 1-h postnatal blood glucose. These findings suggest that subsequent clinical management and obstetric factors, particularly gestational age at delivery and delivery mode, may be more important than the diagnostic OGTT value itself for neonatal glycemic outcomes.