Overweight Women Are More Likely to Have Large Babies

Whether a woman is overweight or obese before and during pregnancy, and not glucose levels, is the most reliable predictor of a woman’s risk of giving birth to a large-for-gestational-age infant, according to a new study conducted in Canada.¹

Included in the study were 472 women who did not have gestational diabetes, per the results of an oral glucose tolerance test administered during late pregnancy. Of these 472 women, 104 (22%) had gestational impaired glucose tolerance.1 The researchers measured fasting levels of insulin, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, leptin, adiponectin, and C-reactive protein. Obstetric outcomes and the birth weight of the neonate were assessed at delivery.

The mean birth weight was 3481 grams (7 lb 11 oz), and 68 infants were large for gestational age (defined as a newborn weight in the 90th percentile or above on Canadian fetal growth charts, or more than 3992 grams [8 lb 13 oz]).¹ After multiple analyses, the study authors found that maternal obesity and leptin levels were more strongly predictive of a woman having an infant who is large for gestational age than glucose intolerance and lipid levels.

Maternal diabetes has long been considered the most common cause of large-for-gestational-age infants. Delivery problems associated with a baby who is large for gestational age are prolonged vaginal delivery, difficult birth, and an increased risk of cesarean section. Infants who are large for gestational age are at greater risk for birth injuries and complications of low blood glucose levels after delivery.²

The results of this new study are important because the International Association of Diabetes in Pregnancy Study Groups have proposed new criteria to lower the glucose level cutoff for diagnosing gestational diabetes as a means to better identify which women are at risk for having large infants.³ If this proposed criteria were to become standard clinical practice, the rate of women identified as having gestational diabetes would double. Of concern is that the designation of gestational diabetes alone, irrespective of how well glucose levels are controlled, may lead to increased interventions. The results of this new study suggest that focusing on weight management may be a better strategy to reduce the risk of having large babies.¹

Pertinent Points:

- Glucose levels are not a significant independent predictor of having a large baby.
- Among women without gestational diabetes, maternal obesity and leptin levels are strong metabolic determinants of having an infant who is large for gestational age.

References:

References
1. Retnakaran R, Ye C, Hanley AJ, et al. Effect of maternal weight, adipokines, glucose intolerance and lipids on infant birth weight among women without gestational diabetes mellitus. CMAJ. 2012;Epub ahead of print.
2. Carlo WA. Large for gestational age infants. In: Kleigman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia: Saunders Elsevier; 2011:chap 91.4.
3. International Association of Diabetes and Pregnancy Study Groups. International Association of Diabetes and Pregnancy Study Groups recommendations on the diagnosis and classification of hyperglycemia in pregnancy. Diabetes Care. 2010;33:676-682.