Decreased maternal lipolysis in intrauterine growth restriction in the third trimester

Abstract

Objective Intrauterine growth restriction (IUGR) is a common complication of pregnancy. There are many possible aetiologic factors of maternal, placental and/or fetal origin. Often there is no known explanation. The aim of this study was to investigate whether a reduction in maternal energy substrate production could be one of the factors involved in IUGR. Design Measurement of maternal energy substrate production and glucoregulatory hormones in women with growth‐restricted fetuses. Settings University Hospital, Uppsala, Sweden. Population Ten healthy pregnant women with IUGR were compared with eight recently reported healthy women with normal pregnancies. The women were studied at 35.4 ± 1.6 weeks of gestation after an overnight fast. Methods Rates of glycerol and glucose production were analysed by gas chromatography/mass spectrometry following constant‐rate infusion of [1,1,2,3,3‐ 2 H 5 ]glycerol and [6,6‐ 2 H 2 ]glucose. Main outcome measure Third trimester glycerol and glucose production. Results Glycerol production, reflecting lipolysis, was lower in the women with IUGR than in those with normal pregnancies, 2.36 ± 0.58 versus 3.06 ± 0.66 μmol kg −1 minute −1 ( P = 0.033), whereas there was no difference in rate of glucose production (glucose production rate [GPR]), 12.1 ± 1.5 versus 13.2 ± 1.5 μmol kg −1 minute −1 ( P = 0.23). Plasma glycerol levels were increased in the women with IUGR ( P = 0.008). Conclusions Lipolysis is lower in pregnancies complicated by IUGR as compared with normal pregnancies. Increased lipolysis during pregnancy provides substrate for maternal energy metabolism, which spares glucose for the fetus. A reduced maternal production of energy substrate could be one of several factors underlying IUGR. A lack of relationship between insulin levels and either lipolysis or GPR suggests defective regulation of energy substrate production in this group of pregnant women.