The effect of bedtime snacks on morning fasting blood glucose in gestational diabetes mellitus: a randomized controlled trial.

IMPORTANCE

While guidelines recommend bedtime snacks for women with gestational diabetes mellitus (GDM), there is insufficient evidence championed those recommendation.

OBJECTIVE

To evaluate if bedtime snacking is effective in preventing high fasting blood glucose incidence among women with GDM.

DESIGN

An open-label, parallel-group, randomized controlled trial was conducted from December 2023 to July 2024 at Ma'anshan Maternal and Child Health Care Center, Anhui, China.

INTERVENTIONS

A total of 62 GDM cases at the nutrition clinics were enrolled, and were randomly and equally allocated to groups of bedtime snacks (25 g nuts, intervention group) and no bedtime snacks (control group). The intervention was lasted for 8 weeks, during which fasting blood glucose was measured 3 times per week, 1-hour postprandial glucose and 2-hour postprandial glucose 2 times per week with a home glucometer. In the late pregnancy (approximately at 34 weeks), the glycated haemoglobin, high-density lipoprotein, low-density lipoprotein, triglycerides, total cholesterol were measured in the laboratory and birth outcomes information (birth weight, gestational weeks at delivery, delivery mode) were collected.

MAIN OUTCOMES AND MEASURES

The primary outcomes were the level of fasting blood glucose and the hyper-fasting blood glucose incidence during 8-week duration. The secondary outcomes were the level of the glycated haemoglobin, high-density lipoprotein, low-density lipoprotein, triglycerides and total cholesterol in the late pregnancy. Generalized estimating equations and analysis of covariates were conducted for the analysis of the primary outcomes. The multivariate linear regression was conducted for the analysis of the secondary outcomes. Post-hoc analysis was also conducted for the indicators of 1-hour postprandial glucose, 2-hour postprandial glucose and perinatal outcomes applying generalized estimating equations, analysis of covariates, the multivariate linear regression and logistics regression.

RESULTS

After adjusting for maternal age, pre-pregnancy body mass index, mid-pregnancy glucose, mid-pregnancy blood lipids and diet in late pregnancy, neither the average fasting blood glucose (control group: 4.90 mmol l, intervention group: 4.96 mmol l) (β = 0.05, [95%CI-0.22 to 0.31], P = 0.720) nor hyper-fasting blood glucose incidence (control group: 0.19, intervention group:0.26) (β = 0.07, [95%CI-0.07 to 0.20], P = 0.335) were significant different between the two groups. And we found low-density lipoprotein level were higher in the intervention group (3.21 mmol l) compared to the control group (2.52 mmol l) (β = 0.70, [95%CI0.07 to 1.34], P = 0.031). Additionally, post-hoc analysis showed that the incidence of elevated 1-hour postprandial glucose was significantly higher in the intervention group (0.42) than in the control group (0.28) (β = 0.14, [95%CI0.01 to 0.27], P = 0.036). No difference was found regarding any perinatal outcomes between the two groups.

CONCLUSIONS

Bedtime snack did not reduce the risk of morning hyperglycaemia and adverse perinatal outcomes in women with gestational diabetes mellitus, but exacerbated lipid markers and the 1-hour postprandial glucose profile. Our study did not support clinicians and relevant guidelines to recommend bedtime snacking as a form of glycaemic control in women with GDM. Clinical trial identification number: ChiCTR2300078399. URL of the registration site: https://www.chictr.org.cn/bin/project/edit?pid=210400 .