Epigenetic aspects of human reproduction and early pregnancy

Epigenetic regulation of molecular reproduction in human and animal models has a profound impact on phenotypic heterogeneity, response to extrinsic factors, and overall health and disease. Epigenetic processes influence all stages of the life cycle, from gametogenesis through organismal aging, and utilize multiple mechanisms of epigenetic inheritance.

In this chapter, we discuss the major principles and processes of molecular epigenetics. These epigenetic changes may last through cell divisions for the duration of cell's life and may last for multiple generations without involving changes in the underlying DNA sequence. DNA methylation and histone modification will be discussed, presenting the mechanisms of covalent modification, RNA transcripts, and microRNAs.

Epigenetic regulation of embryonic development and epigenetic reprogramming will be analyzed in detail with reference to sporadic or transgenerational inheritance. We will also discuss environmental and maternal factors during pregnancy that influence developmental origins of health and disease (DOHaD) of humans. These factors can affect development of the next generation even before conception and can continue throughout pregnancy, early childhood, or into adult life.

Epigenetic changes in children born after ART are discussed with data concerning epigenetic syndromes and epigenetic conditions that are resolved by adulthood.

Finally, psychological conditions during pregnancy can influence adverse birth outcomes, long-term defects of cognitive development, behavioral problems during childhood, and constant high baseline levels of stress-related hormones.