Increased second trimester maternal glucose levels are related to extreme large-for-gestational age infants in women with type 1 diabetes mellitus

Abstract

Abstract Objective Large-for-gestational age infants (LGA, birth weight ≥90^th centile) are a continuing problem in pregnancies of women with type 1 diabetes. We used a continuous glucose monitoring system (CGMS) to assess the relationship between 24-hour diurnal glucose profiles in all three trimesters of the pregnancy and infant birth weight.

Abstract Research Design and Methods Twenty-nine pregnant women with diabetes used the CGMS during each trimester of pregnancy. The glucose profiles of the women with a normal weight infant or a LGA infant were compared.

Abstract Results 48% of the women with diabetes gave birth to a LGA infant. 50% of these infants were already large-for-dates on ultrasound <30 weeks of gestation (early LGA) and all these infants had a birth weight ≥97.7^th centile. The diurnal glucose profiles show that the mothers of early LGA infants had elevated glucose levels for most of the day during the second trimester (p<0.05). The median 24-hour glucose level was significantly higher in women who gave birth to early LGA infants in all three trimesters of pregnancy (6.7, 8.3, 6.5 mmol/l, respectively). Within the group of women with early LGA infants the second trimester median glucose level was significantly higher than that in the first and third trimester (p<0.05).

Abstract Conclusions In women with type 1 diabetes extreme growth of the fetus starts early in pregnancy and this is likely to be caused by increased maternal glucose levels. Further investigation is needed to see whether early tight glycaemic control will reduce the number of extreme LGA infants.