Maternal rates of lipolysis and glucose production in late pregnancy are independently related to fetal weight

Abstract

Objective

Associations between maternal glucose levels and increased fetal growth are well established and independent relationships with maternal weight, weight gain and insulin resistance are also observed. The relative roles of lipolysis and glucose production in the determination of these observations remain unclear.

Design

We examined, through detailed physiological studies, the relationship between maternal late gestational energy substrate production (glucose and glycerol), maternal weight and weight gain, and estimated fetal size in the third trimester.

Patients

Twenty-one nulliparous pregnant women, without gestational diabetes (GDM) assessed at 28 weeks with oral glucose tolerance test, were recruited.

Measurements

Rates of hepatic glucose production (GPR) and rates of glycerol production (reflecting lipolysis) using [¹³C₆]-glucose and [²H₅]-glycerol were measured at 34-36 weeks gestation. Respiratory quotient was assessed by indirect calorimetry and body composition by measurements of total body water (H₂¹⁸O) and body density (BODPOD). Fetal weight was estimated from ultrasound measures of biparietal diameter, femoral length and abdominal circumference.

Results

At 34-36 weeks bivariate analyses showed that GPR and lipolysis correlated with estimated fetal (r=0.71 and 0.72 respectively) as well as with maternal weight, fat mass and fat free mass, but not maternal weight gain. In multivariate analyses rates of both glucose production (r=0.43*) and lipolysis (r=0.46*) were independently associated with fetal size explaining 60% of the variance.

Conclusions

Both maternal rates of lipolysis and hepatic glucose production in late gestation are strongly related to estimated fetal weight.

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