Association of maternal hypoglycemia with low birth weight and low placental weight: a retrospective investigation.

CONTEXT The effects of maternal hypoglycemia on birth weight, placental weight, and placental ratio are unclear. A reliable indicator for increased risk of low birth weight or associated low placental weight could prove invaluable in caring for newborns who are small for gestational age. OBJECTIVE To retrospectively review 2 years of hospital obstetric records for evidence of an association between maternal hypoglycemia (< fifth percentile at 24-week 1-hour glucose challenge test) and birth weight, placental weight, or placental ratio. METHODS Medical center records were reviewed for women who delivered a term newborn between July 1, 2005, and July 31, 2007. Women included in the study were younger than 35 years and had completed a 1-hour glucose challenge test during pregnancy. Excluded were women with comorbid conditions that may be associated with abnormal birth weight and women with serum glucose levels greater than 135 mg/dL. RESULTS Newborns of women with hypoglycemia weighed, on average, significantly less than newborns of women with normal blood glucose levels (t test P=.011). Relative risk was 5.81 (95% confidence interval, 1.25-27.03). Placentas of women with hypoglycemia were also lighter than those of the women in the control group, but the difference was not significant (t test P=.1089). Differences in placental ratios between the 2 groups were not statistically significant (P=.8171). CONCLUSION Lower serum glucose levels during pregnancy might be a causative factor, rather than merely a risk factor, for lower birth weights.