Influence of diet on glycemic control in pregnant women with type 1 diabetes

This study examined the effects of carbohydrate consumption on control of blood glucose levels (glycemic control) during early pregnancy in women with type 1 diabetes (T1D). The study concluded that lower carbohydrate consumption, and carbohydrate counting, improved glycemic control during early pregnancy.

T1D during pregnancy is associated with an increased risk of undesirable events in the children. Higher risks of birth defects are associated with higher HbA1c levels (measures average blood glucose over the past 3 months) during early pregnancy. HbA1c levels of less than 6.5% are recommended.

The amount of carbohydrates consumed is the most important dietary factor affecting glucose levels after a meal. Other factors like the glycemic index (measures how fast a food causes blood glucose levels to rise) are also important. Foods with a low glycemic index are recommended. 

Carbohydrate counting can be a useful method for improving blood glucose control outside of pregnancy. It is not clear whether the type of daily carbohydrates consumed or carbohydrate counting make a difference in blood glucose control during pregnancy.

107 women with T1D were asked to complete a form recording their diet for 3 days. A dietician used the form to estimate the total amount of carbohydrates consumed every day, and to estimate the amount with a high glycemic index. HbA1c levels were measured. The number of snacks eaten daily, the number of hypoglycemic episodes (dangerously low blood glucose), and whether the women used carbohydrate counting, were also recorded.

Higher daily carbohydrate consumption was associated with higher HbA1c levels after daily insulin dose and use of an insulin pump were accounted for. Every 100g of carbohydrates consumed daily was linked to a 0.4% rise in HbA1c. After daily insulin dose and use of an insulin pump were considered, the glycemic index was not associated with higher HbA1c levels.

Women who counted carbohydrates daily (45%) had lower HbA1c levels, lower total carbohydrate consumption, and a lower glycemic index score. These women did not have an increased number of hypoglycemic episodes. Women who had at least 3 snacks every day (41%) consumed more carbohydrates, but had similar HbA1c levels as the other women. 

The study concluded that lower carbohydrate consumption, and carbohydrate counting, improved glycemic control during early pregnancy.

The information on diet was self-reported by the participants and may not be completely accurate. Diet was not recorded for more than 3 days, and thus may not give a full picture of the participants’ overall diet. Furthermore, less than half of the participants recorded their diet for the full 3 days. 25% recorded their diet for only 1 day. Important data on protein and fat intake, as well as physical activity, were not included.

It is important to note that a minimum intake of 175g carbohydrates per day during healthy pregnancy is recommended. The amount of carbohydrates needed by individuals depends on their weight, size, and level of physical activity. More carbohydrates are probably needed in late pregnancy than early pregnancy.

Discuss diet and carbohydrate consumption with your physician if you have T1D and become, or are considering becoming, pregnant.