Poster Presentation The Annual Scientific Meeting of the Endocrine Society of Australia and the Society for Reproductive Biology 2014

Sexual dimorphism at midgestation: recapitulation of hallmarks of growth restriction in normal female fetuses (#339)

Consuelo Estrella 1 2 , Karen Kind 1 2 , Ruidong Xiang 1 2 , Vicki Clifton 2 3 , Claire Roberts 2 3 , Stefan Hiendleder 1 2
  1. School of Animal and Veterinary Sciences, The University of Adelaide, Roseworthy, South Australia, Australia
  2. Robinson Research Institute, The University of Adelaide, Adelaide, South Australia, Australia
  3. School of Paediatrics and Reproductive Health, The University of Adelaide, Adelaide, South Australia, Australia

Sex-specific patterns in fetal biometric indices and their ratios (Melamed Nir et al., 2013) indicate that males and females employ different growth strategies.  Although a number of studies have investigated sexual dimorphism during the prenatal period there is a paucity of data linking sex-specific differences in placental and fetal characteristics with sex-specific strategy for growth during uncomplicated pregnancy.  We used a bovine model to generate normal male (n=27) and female (n=45) concepti recovered at Day 153 gestation (55% term).  Male fetuses were heavier (P<0.0001) with heavier placentas (P<0.05) and organ weights (P<0.0001 ‒ P<0.05), and greater fetus weight:placenta weight ratio (P<0.01).  However, hallmarks of fetal growth restriction, brain:fetus- (P<0.0001) , heart:fetus- (P<0.005) and brain:liver weight ratios (P<0.001) were higher in females.  Umbilical cord, (P<0.01) and artery (P<0.005) and vein (P<0.05) diameters were larger in males.  Placenta weight was positively correlated with fetus weight in both sexes (P<0.0001).  We observed positive relationships between fetal weight and cord vessel diameters (P<0.001) and negative relationships between umbilical artery diameter and brain:liver (P<0.01) and brain:fetus (P<0.005) weight ratios in females. Brain weight appeared to be independent of placental and cord characteristics in males, but not in females (P<0.0001-P<0.005).  Our study therefore demonstrates that growth of key organs such as the brain and heart are spared in the female bovine fetus at midgestation.  A smaller placenta and smaller cord vessel diameters are likely to limit blood flow, which may lead to a redistribution of blood flow to favour delivery of oxygen and nutrients to the brain and heart in females.  A previous study has reported  sex-specific differences in some measures of fetal hemodynamics assessed via ultrasonography in late gestation human fetuses (Verburg et al., 2008). In conclusion, our results show that normal female fetuses exhibit hallmarks of asymmetric growth restriction at midgestation.

  1. MELAMED NIR, MEIZNER ISRAEL, MASHIACH REUVEN, WIZNITZER ARNON, GLEZERMAN MAREK & YARIV, Y. 2013. Fetal sex and intrauterine growth patterns. Journal of Ultrasound in Medicine, 32, 35-43.
  2. VERBURG, B. O., JADDOE, V. W. V., WLADIMIROFF, J. W., HOFMAN, A., WITTEMAN, J. C. M. & STEEGERS, E. A. P. 2008. Fetal Hemodynamic Adaptive Changes Related to Intrauterine Growth: The Generation R Study. Circulation, 117, 649-659.