EFFECT OF MATERNAL CARBOHYDRATE-METABOLISM ON FETAL GROWTH

Objective: To determine the effect of maternal carbohydrate metabolism and anthropometric characteristics on fetal growth. Methods: Eight pr egnant women in the third trimester with unexplained fetal growth rest riction (FGR) and II women with normal pregnancies in the third trimes ter were evaluated for maternal carbohydrate metabolism, using oral gl ucose tolerance tests and hyperinsulinemic-euglycemic clamps. These da ta and maternal anthropometric characteristics subsequently were relat ed to relative birth weight, defined as observed birth weight x 100/50 th percentile birth weight. Results: The women with FGR pregnancies we re more insulin sensitive than were controls (21.6 +/- 4.4 versus 16.7 +/- 4.8 mu mol/kg x min, P <.05) and showed reduced insulin and gluco se areas under the curve (96,293 +/- 25,870 versus 145,291 +/- 49,356 pmol/L, P < .03; 1057.0 +/- 184.7 versus 1210.1 +/- 85.9 mmol/L, P < . 05, respectively). No differences were seen in fasting plasma glucose, insulin and human placental lactogen samples, age, height, pregravid weight, weight gain, and parity. In all patients, maternal insulin sen sitivity and weight gain correlated well with relative birth weight (r = -.65, P < .002; r = .68, P < .001, respectively). When the same ana lysis was computed separately in the groups, insulin sensitivity exhib ited a strong negative correlation with relative birth weight in the F GR group but not in controls (r = -.84, P < .007; r = -.54, P = .08, r espectively). Conversely, in control women the best correlation betwee n relative birth weight and the other variables studied was seen with maternal weight gain (r = .82, P < .002). Conclusion: Women with unexp lained FGR have a different glucose metabolic pattern than do normals. We speculate that increased insulin sensitivity leads to a reduction in metabolic substrates for fetal growth. (C) 1998 by The American Col lege of Obstetricians and Gynecologists.