Carbohydrate Intake Key to Glycemic Control in Pregnant Women With T1D, Data Show

Among pregnant women with type 1 diabetes (T1D), carbohydrate intake appears to play a bigger role in glycemic control than body mass index (BMI) or gestational weight gain, a new study has found.

The findings could change the way physicians monitor and advise patients with T1D. The report was published in the Journal of Human Nutrition and Dietetics.

The problem of excessive weight and obesity among pregnant women appears to be getting worse, explained corresponding author Alyson Hill, PhD, of the University of Ulster in the United Kingdom and colleagues. In the United Kingdom, 28% of pregnant women are considered overweight, and 17% are obese.

“However, the prevalence is reported to be higher in women with diabetes, although there is limited data available for comparison,” the investigators noted.

That is a particular problem since both high pre-pregnancy BMI and T1D are considered risk factors for adverse pregnancy outcomes; when a patient has both risk factors, Hill and colleagues said, the risk is even higher.

Women with T1D who are pregnant are typically instructed to optimize their glycemic control through glucose monitoring, insulin adjustment, and dietary control. Their gestational weight gain is also closely monitored.

However, the investigators wanted to see whether carbohydrate intake might also be an important factor in glycemic control for this patient group. They noted that carbohydrate intake is the key influencer of post-meal hyperglycemia, and some evidence has suggested that low carbohydrate intake might help patients manage their T1D, though the investigators said the current literature on that question is inconclusive.

The American Diabetes Association (ADA) currently recommends a moderate carbohydrate diet to ensure sufficient glucose for the mother and fetus, but Hill and colleagues wanted to know whether non-optimal levels of carbohydrate intake might have negative impacts on glycemic control.

“The aim of this current study was to enhance the evidence base in this area by exploring the relationships between body mass index, carbohydrate intake, and glycemic control in pregnant women with T1D,” the authors wrote.

The investigators performed a secondary analysis of data from 547 pregnant women who participated in a previous study that looked at antioxidant supplementation to prevent pre-eclampsia. The patients in the study had blood samples analyzed for glycated hemoglobin (A1C) at both 26 weeks and 34 weeks; they also completed food questionnaires at 26-28 weeks.

The patients included in the analysis were mostly White (98%) and had a mean age of 29.4 years. Their average duration of diabetes was 11.8 years. Their average BMI at baseline (before 16 weeks gestation) was 26.7 kg/m2.The majority were either overweight (43%) or obese (20%).

After adjusting for insulin dose, the authors found links between A1C and carbohydrate quantity and quality, but the same was not true for BMI.

“Carbohydrate was the strongest predictor of glycemic control (>48mmol/mol) at this time with the highest quintile of carbohydrate (>264g/day) being the strongest predictor (P=.002) of higher A1C,” the authors wrote. “Duration of diabetes was a significant determinant (P=.012), however BMI and age were not found to be significant determinants.”

Virtually all of the women in the study (96%) had higher levels of carbohydrate intake than what the ADA recommends (175 g/day), and carbohydrates made up 55% of the participants’ total energy intake. Seventy percent of the women in the study gained more than the optimal level of gestational weight gain, the authors added.

The investigators cautioned that their study only reflects a particular period in pregnancy, and thus the associations between weight, carbohydrate intake, and glycemic control may vary at other stages in pregnancy. They also said physicians should continue to provide pre-pregnancy counseling to women with T1D, and to emphasize the importance of weight control. However, the investigators said carbohydrate intake should be part of the conversation, too.

“This present study suggests that monitoring quantity and type of carbohydrate consumed (and matching insulin doses) may have an impact on glycemic control and be an important strategy to optimize glycemic control,” Hill and colleagues concluded.

Reference:

Hill AJ, Patterson C, Young IS, Holmes VA, McCance DR. Carbohydrate quantity is more closely associated with glycaemic control than weight in pregnant women with type 1 diabetes; insights from the Diabetes and Pre-eclampsia Intervention Trial (DAPIT). J Hum Nutr Diet. Published online May 25, 2022. doi:10.1111/jhn.13042