Glucose levels measured with continuous glucose monitoring in uncomplicated pregnancies

Abstract

Introduction: To characterize glucose levels during uncomplicated pregnancies, defined as pregnancy with a hemoglobin A1c <5.7% (<39 mmol/mol) in early pregnancy, and without a large-for-gestational-age birth, hypertensive disorders of pregnancy, or gestational diabetes mellitus (ie, abnormal oral glucose tolerance test).

Research design and methods: Two sites enrolled 937 pregnant individuals aged 18 years and older prior to reaching 17 gestational weeks; 413 had an uncomplicated pregnancy (mean±SD body mass index (BMI) of 25.3±5.0 kg/m²) and wore Dexcom G6 continuous glucose monitoring (CGM) devices throughout the observed gestational period. Mealtimes were voluntarily recorded. Glycemic levels during gestation were characterized using CGM-measured glycemic metrics.

Results: Participants wore CGM for a median of 123 days each. Glucose levels were nearly stable throughout all three trimesters in uncomplicated pregnancies. Overall mean±SD glucose during gestation was 98±7 mg/dL (5.4±0.4 mmol/L), median per cent time 63-120 mg/dL (3.5-6.7 mmol/L) was 86% (IQR: 82-89%), median per cent time <63 mg/dL (3.5 mmol/L) was 1.8%, median per cent time >120 mg/dL (6.7 mmol/L) was 11%, and median per cent time >140 mg/dL (7.8 mmol/L) was 2.5%. Mean post-prandial peak glucose was 126±22 mg/dL (7.0±1.2 mmol/L), and mean post-prandial glycemic excursion was 36±22 mg/dL (2.0±1.2 mmol/L). Higher mean glucose levels were low to moderately associated with pregnant individuals with higher BMIs (103±6 mg/dL (5.7±0.3 mmol/L) for BMI ≥30.0 kg/m² vs 96±7 mg/dL (5.3±0.4 mmol/L) for BMI 18.5-<25 kg/m², r=0.35).

Conclusions: Mean glucose levels and time 63-120 mg/dL (3.5-6.7 mmol/L) remained nearly stable throughout pregnancy and values above 140 mg/dL (7.8 mmol/L) were rare. Mean glucose levels in pregnancy trend higher as BMI increases into the overweight/obesity range. The glycemic metrics reported during uncomplicated pregnancies represent treatment targets for pregnant individuals.

Keywords: Pregnancy; Reproductive Health; Research.

Figure 1

Distribution of CGM-measured glucose levels throughout uncomplicated pregnancies. Envelope plots of the per cent of CGM values within each glucose level interval for each participant during (A) the entire observed gestational period (N=413) and (C) each trimester (N=118, 413, and 355 in the first, second, and third trimester, respectively). Tracings of participant-level mean glucose levels by the hour of the day during (B) the entire observed gestational period and (D) each trimester. Solid dots and lines represent medians, and open circles represent means. Shaded bands represent the IQR (ie, 25th–75th percentiles). The first, second, and third trimesters are represented by the colors blue, red, and green, respectively. CGM, continuous glucose monitoring.