Blood sugar issues and pregnancy...

In women with poorly controlled Type 2 Diabetes (T2D) or women without T2D, but have poorly regulated blood sugar based on HbA1c levels, pregnancy raises health concerns as hyperglycemia (uncontrolled blood glucose) increases the risk of birth defects and maternal complications.

In women without pre-existing type 2 diabetes (T2D), elevated HbA1c in the first trimester predicted a 3-fold increased risk of adverse pregnancy outcomes such as macrosomia, a new prospective study found.1

HbA1c ≥ 6.5% is one of the diagnostic criteria of T2D. In women with poorly controlled T2D, pregnancy raises health concerns as hyperglycemia (uncontrolled blood glucose) increases the risk of birth defects and maternal complications.2 But what about mothers-to-be who do not have T2D (HbA1c < 6.5)? Researchers from the Department of Endocrinology and Nutrition at Hospital del Mar (Barcelona, Spain) collected HbA1c data early on from a multi-ethnic cohort consisting of 1228 non-diabetic women, and evaluated their pregnancy outcomes.

They found that an early pregnancy HbA1c of 5.9-6.4% was linked to a 3-fold increased risk of macrosomia (newborns with birth weight ≥ 4,000 grams, or 8 pounds and 13 ounces) and a tendency towards pre-eclampsia, compared with those with HbA1c < 5.9%. It did not matter whether or not these women developed gestational diabetes later in pregnancy.

The researchers believed that first-trimester HbA1c with a cutoff point of 5.9% can help identify women at high risk for poorer pregnancy outcomes, and HbA1c is a valuable additional tool in appraising glycemic status during pregnancy.

The study results were published in the Journal of Clinical Endocrinology & Metabolism (December 2016).

Why is this clinically important?

Fetal development during the first trimester is critical, as this is the period when all of the major organ systems are forming and the fetus is most vulnerable to damage from substances including high blood glucose.

The American Diabetes Association states that excellent glycemic control in the first trimester continued throughout pregnancy is associated with the lowest frequency of maternal, fetal, and neonatal complications. Thus, glycemic control through dietary modification should begin 2-3 months before getting pregnant. Women should test for HbA1c as part of the family planning and the first prenatal visit.

For women without pre-existing diabetes, it is preferable to maintain HbA1c < 5.9% prior and during the first trimester.

References

1. Mane, L, et al., Role of first trimester HbA1c as a predictor of adverse obstetric outcomes in a multi-ethnic cohort. J Clin Endocrinol Metab, 2016: p. jc20162581.
2. Correa, A, et al., Diabetes mellitus and birth defects. Am J Obstet Gynecol, 2008. 199(3): p. 237 e1-9.