The impact of maternal diabetes on birth to placental weight ratio and umbilical cord oxygen values with implications for fetal-placental development.

INTRODUCTION

We determined the impact of gestational diabetes (GDM) and pre-existing diabetes (DM) on birth/placental weight and cord oxygen values with implications for placental efficiency and fetal-placental growth and development.

METHODS

A hospital database was used to obtain birth/placental weight, cord PO and other information on patients delivering between Jan 1, 1990 and Jun 15, 2011 with GA >34 weeks (N = 69,854). Oxygen saturation was calculated from the cord PO and pH data, while fetal O extraction was calculated from the oxygen saturation data. The effect of diabetic status on birth/placental weight and cord oxygen values was examined adjusting for covariates.

RESULTS

Birth/placental weights were stepwise decreased in GDM and DM compared to non-diabetics with placentas disproportionally larger indicating decreasing placental efficiency. Umbilical vein oxygen was marginally increased in GDM but decreased in DM attributed to the previously reported hyper-vascularization in diabetic placentas with absorbing surface area of capillaries initially increased, but then constrained by increasing distance from maternal blood within the intervillous space. Umbilical artery oxygen was unchanged in GDM and DM, with fetal O extraction decreased in DM indicating that fetal O delivery must be increased relative to O consumption and likely due to increased umbilical blood flow.

DISCUSSION

Increased villous density/hyper-vascularization in GDM and DM with placentas disproportionately larger and umbilical blood flow increased, are postulated to normalize umbilical artery oxygen despite increased birth weights and growth-related O consumption. These findings have implications for mechanisms signaling fetal-placental growth and development in diabetic pregnancies and differ from that reported with maternal obesity.