First Trimester Mean Glucose Level on Continuous Glucose Monitoring Is Associated with Infant Birth Weight.

Background: Comparisons between continuous glucose monitoring (CGM) metrics during the first and second trimesters and conventional mid-pregnancy oral glucose tolerance test (OGTT) values in pregnant women without pre-existing diabetes for predicting infant birth weight are scarce.

Methods: In a longitudinal observational study, 113 participants had first and second trimester CGM data collected over a 7- to 14-day period, as well as three-point OGTT (fasting, 1-hour, and 2-hour) performed at mid-pregnancy (24 to 28 weeks). Multinomial logistic regression, adjusting for maternal ethnicity, education level, age, pre-pregnancy body mass index, parity, gestational diabetes mellitus diagnosis, gestational age at delivery, and type of CGM sensor was used to analyse the relationship between CGM metrics, OGTT glucose values and infant birth weight tertile (Clinical trial identification number: NCT05123248).

Results: In the univariate analysis, CGM-derived metrics including higher mean glucose in the first trimester, higher % time above range in the second trimester, and higher % time in range (TIR) and lower % time below range (TBR) in both the first and second trimesters were associated with infants in the highest birth weight tertile. After adjusting for confounders, a 1-standard deviation increase in mean glucose level during the first trimester was significantly associated with the likelihood of the neonatal birthweight being in the highest tertile (adjusted odds ratio, 3.11; 95% confidence interval, 1.18 to 8.21; P=0.022). No significant associations were found between OGTT glucose values and infant birth weight outcomes.

Conclusion: CGM-derived mean glucose levels in early pregnancy may be a better predictor of an infant's birth weight within the highest tertile, compared to mid-pregnancy OGTT glucose values.