Will a fetus with a large abdominal circumference at 20 weeks gestation, due to gestational diabetes (GDM) diagnosed at 27 weeks, return to a normal size with good glycemic control?

From the Guidelines

With good blood sugar control, the fetus's abdominal circumference may normalize or show improved growth patterns, but it might not completely return to normal range if macrosomia has already developed. When gestational diabetes is diagnosed and well-controlled through diet, as in this case, further excessive fetal growth can often be prevented, though existing growth acceleration may not fully reverse. The timing of intervention is crucial - earlier control of maternal glucose levels typically yields better outcomes for fetal growth parameters, as suggested by the most recent guidelines for managing diabetes in pregnancy 1. The enlarged abdominal circumference at 20 weeks, before the gestational diabetes diagnosis at 27 weeks, suggests that metabolic changes affecting fetal growth were already present before clinical diagnosis. This occurs because fetal macrosomia in diabetic pregnancies results from maternal hyperglycemia causing fetal hyperinsulinemia, which promotes fat deposition particularly in the abdominal area, a concept supported by the management recommendations for gestational diabetes mellitus 1. Even with excellent glucose control after diagnosis, the fetus may continue to have a larger abdominal circumference than average, though the growth trajectory should improve. Key aspects of managing gestational diabetes include lifestyle behavior changes and, if necessary, insulin therapy to achieve glycemic targets, as outlined in the standards of medical care in diabetes-2021 1. Regular ultrasound monitoring every 3-4 weeks is recommended to track fetal growth patterns and assess for any complications related to macrosomia, which can help guide delivery planning and reduce risks of birth complications, in line with the suggestions from the fifth international workshop-conference on gestational diabetes mellitus 1. Additionally, nutrition recommendations and interventions for diabetes, such as adequate energy intake and carbohydrate-controlled meal plans, play a crucial role in managing gestational diabetes and promoting optimal nutrition for maternal and fetal health, as discussed in the position statement of the American Diabetes Association 1. Overall, the management of gestational diabetes should focus on achieving normoglycemia, appropriate weight gain, and absence of ketones, with the goal of minimizing risks to both the mother and the fetus.

From the Research

Fetal Abdominal Circumference in Gestational Diabetes

• The fetus's abdominal circumference is an important measure in assessing fetal growth and development, particularly in pregnancies complicated by gestational diabetes mellitus (GDM) 2, 3.
• Studies have shown that GDM exposure is associated with an increase in fetal growth measures, especially abdominal circumference, which can be detected as early as 16-18 weeks' gestation 3.
• A study found that serial measurements of the fetal abdominal circumference can be used to guide metabolic management of pregnancies complicated by GDM, and that a reduction in the number of repeat ultrasound examinations can save resources 2.

Effect of Good Sugar Control on Fetal Abdominal Circumference

• With good sugar control, the fetus's abdominal circumference may not necessarily become a normal healthy size, as the increased insulin resistance of the mother can still cause the fetus to store extra glucose as body fat, leading to macrosomia 4.
• However, a study found that insulin therapy can reduce the risk of macrosomia in women with mild GDM, and that fetal ultrasound can be used to guide metabolic therapy in these pregnancies 5.
• Another study found that diet-controlled GDM can still result in a lower risk of macrosomia, but the fetus's abdominal circumference may remain larger than normal 3.

Management and Monitoring of Gestational Diabetes

• The diagnosis and management of GDM are crucial in reducing the risk of adverse maternal and neonatal outcomes, including macrosomia, shoulder dystocia, and neonatal hypoglycemia 6.
• Treatment of GDM typically consists of glucose monitoring, dietary modification, exercise, and, when necessary, pharmacotherapy to maintain euglycemia 6.
• Regular monitoring of fetal well-being, including nonstress tests and amniotic fluid indices, is also important in managing pregnancies complicated by GDM 6.