Foetal and placental weights in relation to maternal characteristics in gestational diabetes.

An increased placental weight has been reported in pregnancies complicated with gestational diabetes (GDM). We have analysed foetal (F) and placental weight (P) and foetal length in 143 consecutive normal (N) and 132 GDM pregnancies in relation to type of treatment and to a number of maternal variables. All N pregnancies had a negative oral glucose challenge test at 24-28 weeks. GDM was diagnosed at 28-32 weeks by a 100-gm, 3-h oral glucose tolerance test (OGTT). Treatment was diet (D: n=82) or diet plus insulin (D+I: n=50) according to self-monitoring of blood glucose. A significant difference was observed between N and GDM pregnancies for maternal age (N=30.6+/-5.38 years; GDM=33.2+/-4.53 years; P< 0.001), pre-pregnancy weight (N=58.2+/-8.0 kg; GDM=63.0+/-12.9 kg; P< 0.001) and BMI (N= 21.9+/-2.63; GDM=24.4+/-4.71;P< 0.001). Foetal weight became significantly higher in the GDM group (N=3274.2+/-296.0 g; GDM=3287.1+/-474.1g; P< 0.05) once correction was made for the significant difference in gestational age between the two groups (N=39.4+/-1.17 weeks; GDM=38.8+/-1.39 weeks; P< 0.001). Significantly higher placental weights (N=561.87+/-91.0 g; GDM=592.2+/-115.8 g;P< 0.01) and significantly lower F/P weight ratios were found in GDM pregnancies (N=5.96+/-1.02; GDM=5.69+/-1.13; P< 0.05). In GDM pregnancies a significantly negative correlation was found between the OGTT response and weights of foetus and placentae at delivery, suggesting that both foetal and placental growth are affected by maternal insulin resistance.