Sexual dimorphism in placental development and function: Comparative physiology with an emphasis on the pig

Across mammalian species, it has been demonstrated that sex influences birth weight, with males being heavier than females; a characteristic that can be observed from early gestation. Male piglets are more likely to be stillborn and have greater preweaning mortality than their female littermates, despite the additional maternal investment into male fetal growth. Given the conserved nature of the genome between the sexes, it is hypothesized that these developmental differences between males and females are most likely orchestrated by differential placental adaptation. This review summarizes the current understanding of fetal sex-specific differences in placental and endometrial structure and function, with an emphasis on pathways found to be differentially regulated in the pig including angiogenesis, apoptosis, and proliferation. Given the importance of piglet sex in agricultural enterprises, and the potential for skewed litter sex ratios, it is imperative to improve understanding of the relationship between fetal sex and molecular signaling in both the placenta and endometria across gestation.

Automated summary

Sex influences birth weight, with males being heavier than females. Male piglets have higher stillbirth rates and preweaning mortality, despite more maternal investment. Current research indicates that there are sex-specific differences in placental and endometrial structure and function, affecting pathways such as angiogenesis, apoptosis, and proliferation. Understanding the relationship between fetal sex and molecular signaling in the placenta and endometria is crucial for the agriculture industry and for addressing skewed litter sex ratios.