Sex-specific differences and developmental programming for diseases in later life.

Epidemiological data indicate that developmental programming of various non-communicable diseases (NCDs) occurs as a consequence of altered maternal metabolic and physiological status due to a number of environmental insults during pregnancy. Sex-specific differences have also been reported in most NCDs. Evidence suggests that beginning from conception, the maternal and neonatal metabolic environment, including hormones, contributes to sex-specific placental development. The placenta then regulates the sex-specific differences in NCDs via the epigenetic mechanisms that are further affected by hormones. Male and female embryos have been reported to exhibit sex-specific transcriptional regulation, and it is suggested that their development can be considered as separate processes beginning from conception. This review summarises various animal and human studies examining sex-specific differences in NCDs due to differential placental epigenetic developmental programming. An overview of possible mechanisms underlying this is also discussed. Further, the review describes sex-specific changes in the structure and function of the placenta in pregnancies complicated by fetal growth restriction, pre-eclampsia and preterm birth. Thus, because sex-specific differences are associated with fetal outcome and survival, future studies need to take into consideration the sex of the fetus while explaining the concept of the developmental origins of health and disease.