Gestational diabetes mellitus (GDM) traditionally refers to abnormal glucose tolerance with onset or first recognition during pregnancy. GDM has long been associated with obstetric and neonatal complications primarily relating to higher infant birthweight and is increasingly recognized as a risk factor for future maternal and offspring cardiometabolic disease. The prevalence of GDM continues to rise internationally due to epidemiological factors including the increase in background rates of obesity in women of reproductive age and rising maternal age and the implementation of the revised International Association of the Diabetes and Pregnancy Study Groups’ criteria and diagnostic procedures for GDM. The current lack of international consensus for the diagnosis of GDM reflects its complex historical evolution and pragmatic antenatal resource considerations given GDM is now 1 of the most common complications of pregnancy. Regardless, the contemporary clinical approach to GDM should be informed not only by its short-term complications but also by its longer term prognosis. Recent data demonstrate the effect of early in utero exposure to maternal hyperglycemia, with evidence for fetal overgrowth present prior to the traditional diagnosis of GDM from 24 weeks’ gestation, as well as the durable adverse impact of maternal hyperglycemia on child and adolescent metabolism. The major contribution of GDM to the global epidemic of intergenerational cardiometabolic disease highlights the importance of identifying GDM as an early risk factor for type 2 diabetes and cardiovascular disease, broadening the prevailing clinical approach to address longer term maternal and offspring complications following a diagnosis of GDM.

Lower carbohydrate diets have the potential to improve glycemia but may increase ketonemia in women with gestational diabetes (GDM). We hypothesized that modestly lower carbohydrate intake would not increase ketonemia. To compare blood ketone concentration, risk of ketonemia, and pregnancy outcomes in women with GDM randomly assigned to a lower carbohydrate diet or routine care. Forty-six women aged (mean ± SEM) 33.3 ± 0.6 y and prepregnancy BMI 26.8 ± 0.9 kg/m2 were randomly assigned at 28.5 ± 0.4 wk to a modestly lower carbohydrate diet (MLC, ∼135 g/d carbohydrate) or routine care (RC, ∼200 g/d) for 6 wk. Blood ketones were ascertained by finger prick test strips and 3-d food diaries were collected at baseline and end of the intervention. There were no detectable differences in blood ketones between completers in the MLC group compared with the RC group (0.1 ± 0.0 compared with 0.1 ± 0.0 mmol/L, n = 33, P = 0.31, respectively), even though carbohydrate and total energy intake were significantly lower in the intervention group (carbohydrate 165 ± 7 compared with 190 ± 9 g, P = 0.04; energy 7040 ± 240 compared with 8230 ± 320 kJ, P <0.01, respectively). Only 20% of participants in the MLC group met the target intake compared with 65% in the RC group (P <0.01). There were no differences in birth weight, rate of large-for-gestational-age infants, percent fat mass, or fat-free mass between groups. An intervention to reduce carbohydrate intake in GDM did not raise ketones to clinical significance, possibly because the target of 135 g/d was difficult to achieve in pregnancy. Feeding studies with food provision may be needed to assess the benefits and risks of low-carbohydrate diets. This trial was registered at www.anzctr.org.au as ACTRN12616000018415.

Continuous glucose monitoring is recommended for pregnant women with type 1 diabetes, due to associations with decreased hemoglobin A1c and large for gestational age. However, its benefit in type 2 diabetes and gestational diabetes is not established. This systematic review and meta-analysis compared usage of continuous glucose monitoring to self-monitoring of blood glucose both across and within diabetes in pregnancy and determined which glucose metrics are associated with perinatal outcomes, to potentially inform treatment targets in diabetes in pregnancy. We searched Medline, Embase, CENTRAL, CINAHL, and Scopus, from January 2003 to August 2024. Randomized controlled trials and quasi-experimental studies comparing continuous glucose monitoring with self-monitoring of blood glucose in diabetes in pregnancy were included. Randomized controlled trials and quasi-experimental studies were analyzed separately. Data were extracted on continuous glucose monitoring metrics, hemoglobin A1c, rates of cesarean delivery, large for gestational age, small for gestational age, neonatal hypoglycemia, and neonatal intensive care unit admission, summarized as mean differences or odds ratios with 95% confidence intervals and 95% prediction intervals. Prespecified subgroup analyses were undertaken by diabetes in pregnancy subtype, including duration of continuous glucose monitoring use (continuous vs intermittent) for large for gestational age. Certainty of evidence was assessed using the Grading of Recommendations, Assessment, Development, and Evaluations framework. Across diabetes in pregnancy, continuous glucose monitoring (vs self-monitoring of blood glucose) decreased hemoglobin A1c (mean difference, -0.22% [95% confidence interval, -0.37, -0.08]) (7 randomized controlled trials, moderate-certainty evidence). Within diabetes in pregnancy, continuous glucose monitoring use (vs self-monitoring of blood glucose) showed similar but stronger benefits in both type 1 diabetes when used throughout pregnancy (hemoglobin A1c mean difference, -0.18% [95% confidence interval, -0.36, 0.00]; large for gestational age odds ratio, 0.51 [0.28, 0.90]) (1 randomized controlled trial, high-certainty evidence), and gestational diabetes when used intermittently (hemoglobin A1c mean difference, -0.18 [95% confidence interval, -0.33, -0.02]) (5 randomized controlled trials, moderate-certainty evidence) and large for gestational age (odds ratio, 0.46 [0.26, 0.81]) (1 quasi-experimental study, low-certainty evidence), with insufficient data for continuous glucose monitoring benefit in type 2 diabetes. Increased pregnancy %time-in-range (type 1 diabetes) and decreased mean sensor glucose (type 1 diabetes/gestational diabetes) were associated with decreased large for gestational age. Usage of continuous glucose monitoring (vs self-monitoring of blood glucose) reduces hemoglobin A1c and possibly large for gestational age across diabetes in pregnancy. Greatest benefit was evidenced in type 1 diabetes, followed by gestational diabetes, although continuous glucose monitoring duration differed. Mean sensor glucose and pregnancy %time-in-range are important continuous glucose monitoring metrics for reducing large for gestational age.

This study aims to determine the peak timing of postprandial blood glucose level (PBGL) of two breakfasts with different glycemic index (GI) in gestational diabetes mellitus (GDM). Ten women with diet-controlled GDM who were between 30 and 32 weeks of gestation were enrolled in the study. They consumed two carbohydrate controlled, macronutrient matched bread-based breakfasts with different GI (low vs. high) on two separate occasions in a random order after an overnight fast. PBGLs were assessed using a portable blood analyser. Subjects were asked to indicate their satiety rating at each blood sample collection. Overall the consumption of a high GI breakfast resulted in a greater rise in PBGL (mean ± SEM peak PBGL: low GI 6.7 ± 0.3 mmol/L vs. high GI 8.6 ± 0.3 mmol/L; p < 0.001) and an earlier peak PBGL time (16.9 ± 4.9 min earlier; p = 0.015), with high variability in PBGL time between subjects. There was no significant difference in subjective satiety throughout the test period. In conclusion, the low GI breakfast produced lower postprandial glycemia, and the peak PBGL occurred closer to the time recommended for PBGL monitoring (i.e., 1 h postprandial) in GDM than a macronutrient matched high GI breakfast.

The influence of maternal macronutrient balance and dietary glycemic index (GI) on neonatal body composition has received little study. We hypothesized that the overall quantity and quality of macronutrients, particularly carbohydrate, in the maternal diet could have trimester-specific effects on neonatal growth and body composition in women at risk of gestational diabetes. Maternal diet was assessed using 3-day food records in mid (n = 96) and late (n = 88) pregnancy as part of the GI Baby 3 study. Neonatal body composition was assessed by air-displacement plethysmography within 48 h of birth, adjusted for length, and expressed as fat mass index (FMI) and fat-free mass index (FFMI). In mid pregnancy, higher maternal intake of carbohydrate energy was negatively correlated with infant FFMI (p = 0.037). In late pregnancy, higher dietary GI was associated with lower FFMI (p = 0.010) and higher carbohydrate energy predicted lower FMI (p = 0.034). Higher fat intake (%E) and saturated fat, but not protein, also predicted neonatal body composition (higher FFMI in mid pregnancy and higher FMI in late pregnancy). Depending on pregnancy stage, a high carbohydrate-low fat diet, particularly from high glycemic sources, may reduce neonatal indices of both lean mass and adiposity.