The differential effects of body fat distribution on insulin and glucose metabolism during pregnancy.

OBJECTIVE

Our purpose was to investigate whether maternal obesity, or more specifically body fat distribution, is associated with alterations in carbohydrate metabolism during pregnancy.

STUDY DESIGN

A longitudinal study of oral glucose tolerance tests, insulin, C peptide, and glucagon levels during each trimester and post partum was undertaken in nine lean and 14 obese women. Obese women were divided into lower body obese (n = 6, waist/hip ratio < 0.9) and upper body obese (n = 8, waist/hip ratio > or = 0.9).

RESULTS

Fasting blood glucose levels declined with advancing gestation only in lean subjects. Upper body obese women demonstrated maximal glucose response and insulin area under the curve by the second trimester, whereas lean and lower body obese women did not until the third trimester. Insulin areas were significantly elevated in upper body obese compared with lower body obese women (second trimester, p < 0.01; third trimester, p < 0.03; post partum p < 0.05). In contrast, C peptide levels were similar in obese subgroups and were significantly elevated only when compared with those of lean women. C peptide/insulin molar ratios were lower in upper body obese women during the second trimester (4.3 +/- 0.8) and third trimester (4.2 +/- 0.7) compared with lean (6.5 +/- 1.3, 6.7 +/- 0.5) and lower body obese women (7.9 +/- 1.4, 6.5 +/- 1.4) (p < 0.01). A significant relationship between waist/hip ratio and glucose level (r = 0.70, p < 0.004) and insulin areas (r = 0.76, p < 0.001) was present in late pregnancy in obese subjects.

CONCLUSIONS

Relative hyperinsulinemia and earlier maximal glucose response in upper body obese women suggests that body fat distribution may explain the metabolic heterogeneity present in obese women during pregnancy. Body fat topography may serve as a potential marker for the early development of carbohydrate intolerance during pregnancy.