The Association Between Glucose Intolerance and Longitudinal Fetal Growth in Nulliparas

To evaluate fetal growth patterns and birth weight among individuals with normoglycemia, mild glucose intolerance, and gestational diabetes mellitus (GDM) from midgestation until delivery.

This is a secondary analysis of the NuMoM2b (Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be) prospective cohort of nulliparous individuals with singleton gestations. Maternal glucose tolerance was categorized as normal, mild glucose intolerance (one abnormal Carpenter-Coustan value), or GDM. Blinded ultrasounds at 16-22 weeks and 22-29 weeks provided fetal biometry z scores; suspected large for gestational age (LGA) was defined as an abdominal circumference or estimated fetal weight above the 90th percentile on ultrasound; LGA was confirmed as birth weight above the 90th percentile for gestational age and sex. Logistic regression and covariance pattern models assessed the association between glycemic status and LGA growth across time points.

Among 7,010 included participants, 175 (2.5%) had mild glucose intolerance, and 290 (4.1%) had GDM. Fetal biometry was similar across groups at 16-22 weeks. By 22-29 weeks, GDM was associated with accelerated fetal growth z scores, and both mild glucose intolerance and GDM were associated with increased odds of abdominal circumference above the 90th percentile (adjusted odds ratio [AOR] 1.64, 95% CI, 1.08-2.50 and AOR 1.54, 95% CI, 1.10-2.16, respectively). By delivery, mild glucose intolerance carried a twofold increased risk for LGA birth weight (AOR 2.00, 95% CI, 1.29-3.10), whereas the LGA risk in those with GDM was similar to that in normoglycemic individuals (AOR 1.34, 95% CI, 0.91-1.98).

Fetal overgrowth associated with glucose intolerance emerges around the standard 24- to 28-week GDM screening window. Individuals with GDM had an LGA risk similar to those with normal glucose tolerance, consistent with the increased surveillance and clinical management associated with a GDM diagnosis attenuating the trajectory of excess fetal growth. Whether treatment of mild glucose intolerance can reduce LGA risk remains to be determined.

ClinicalTrials.gov, NCT01322529.