From the Guidelines
Blood sugar control often improves after 36 weeks of gestation in diet-managed gestational diabetes due to several physiological changes, primarily the natural decline in insulin resistance as pregnancy approaches term, as supported by the American Diabetes Association's position statement 1. The primary reason for this improvement is the reduction in placental hormone production, such as human placental lactogen, progesterone, and cortisol, which progressively increase insulin resistance throughout pregnancy to ensure adequate glucose supply to the fetus. However, after 36 weeks, placental function begins to mature and stabilize, leading to reduced hormone production and consequently decreased insulin resistance. Additionally, the following factors contribute to improved blood sugar control:
- Fetal growth rate typically slows during this period, reducing glucose demands
- The placenta becomes slightly less efficient at nutrient transfer as it ages, which can contribute to improved maternal glucose levels
- Some women may also become more compliant with dietary restrictions as they approach delivery, recognizing the importance of glycemic control for a successful birth outcome These combined factors often result in improved blood glucose readings and sometimes allow for reduction in insulin doses for those requiring medication earlier in pregnancy, as noted in the evidence-based nutrition principles and recommendations for the treatment and prevention of diabetes and related complications 1. Key aspects of managing gestational diabetes include:
- Maintaining desirable weight gain during pregnancy
- Avoiding hypocaloric diets, which can result in ketonemia and ketonuria
- Regular aerobic exercise to lower fasting and postprandial glucose concentrations
- Breastfeeding, which is recommended for women with preexisting diabetes or gestational diabetes, as it can help lower blood glucose levels and reduce the risk of subsequent diabetes 1.
From the Research
Reasons for Improved Blood Sugar Control
There are several reasons why blood sugar becomes easier to control and goes lower after 36 weeks of gestation in gestational diabetes managed through diet. Some of these reasons include:
- Changes in insulin sensitivity and glucose metabolism during pregnancy 2
- Increased insulin resistance in early pregnancy, which decreases as the pregnancy progresses 3
- Improved glycemic control through dietary measures and self-monitoring of blood glucose levels 4
- The natural progression of pregnancy, where the body's insulin resistance decreases after 36 weeks of gestation, making it easier to control blood sugar levels 5
Factors Influencing Blood Sugar Control
Several factors can influence blood sugar control in gestational diabetes, including:
- Fasting blood glucose levels and the initiation of insulin therapy 3
- The use of postprandial versus preprandial blood glucose monitoring 5
- The type of antidiabetic treatment used, such as insulin or metformin 6
- Maternal metabolic status, including glycated hemoglobin levels, glycemic profile, and insulin concentration 6
Dietary Management and Blood Sugar Control
Dietary management plays a crucial role in controlling blood sugar levels in gestational diabetes. Studies have shown that:
- Medical nutrition therapy is the cornerstone of management and must be designed to meet individual needs 2
- Self-monitoring of blood glucose should be taught to and performed by all women with gestational diabetes 2
- Dietary treatment can result in satisfactory levels of blood glucose in 90% of women diagnosed with gestational diabetes 4