Exploring the relationship between maternal Continuous Glucose Monitoring "time in range" and fetal abdominal circumference in pregnant women with Type 1 Diabetes.

BACKGROUND

To explore the relationship between maternal glycaemic control and fetal abdominal circumference in pregnancies complicated by T1D.

METHODS

This is a retrospective cohort study of 81 pregnant women with T1D using CGM. Inclusion criteria were T1D, CGM use, ≥2 in-house ultrasounds, and the birth of a live singleton neonate between 1st December 2019 and 1st December 2022. Linear regression analysis was used to assess the cross-sectional relationships between estimated fetal abdominal circumference (AC) on ultrasound and time in range (TIR) at matched time-points in the third trimester of pregnancy. Linear regression analysis was also used to examine whether first trimester TIR and HbA1c predicts third trimester fetal AC.

RESULTS

At baseline, the mean ± standard deviation (SD) of the first trimester HbA1c was 7.0 ± 1.4% and mean ± SD total daily dose (TDD) insulin was 46.6 ± 21.0 units. The mean ± SD birthweight was 3367.0 ± 861.3 grams. There was no cross-sectional relationship between TIR and fetal AC at 28-, 32- or 36-week' gestation. The results of the regression analysis indicate a significant relationship between first trimester TIR (independent predictor) and fetal AC (dependent variable) at 32- and 36-weeks' gestation while controlling for maternal age, BMI, pump use, and TDD insulin (Adjβ= -0.42, 95%CI -0.80 to -0.03 and Adjβ = -0.57, 95%CI -1.02 to -0.12 at 32- and 36-weeks respectively). Although there was a significant relationship between first trimester HbA1c and fetal AC at 32-weeks' gestation (β = 3.81, 95%CI 0.29 to 7.33), the relationship was not significant after adjustment for confounders.

CONCLUSIONS

There was no cross-sectional relationship between TIR and fetal AC in the third trimester of pregnancy but first trimester TIR did predict fetal AC in late pregnancy.