Epigenetic risks related to assisted reproductive technologies: risk analysis and epigenetic inheritance.

A broad spectrum of assisted reproductive technologies has become available for couples with fertility problems. Follow-up studies of children born as a result of assisted reproduction have shown that neonatal outcome and malformation rates are not different from those of the general population, except for a low birthweight and a slight increase in chromosomal abnormalities. The safety aspect of assisted reproduction at the epigenetic level has not been well studied. Epigenetics refers to phenomena where modifications of DNA methylation and/or chromatin structure underlie changes in gene expression and phenotype characteristics. This article intends to analyse epigenetic risks related to assisted reproduction on the basis of an overview of epigenetic reprogramming events in the gamete and early embryo. Two epigenetic modifications, methylation and imprinting, are considered in more detail. The interference of in-vitro embryo culture, immature sperm cells and nuclear transfer with epigenetic reprogramming is discussed, as well as the possibility of epigenetic inheritance.