DNA methylation is a mechanism used by cells to control gene expression which involves the binding of a methyl group to DNA. The addition of methyl groups to DNA switches genes off which in turn inhibits protein production. The addition and removal of methyl groups from DNA occur throughout the lifetime of an individual. Changes in DNA methylation can be induced by any of the treatments used within the IVF procedures including hormone treatment and changes in the culture medium in which the embryos develop.
'Our study found only small differences in DNA methylation at birth and these were not seen in early childhood. When considered along with our previous studies finding no differences in children's growth and development, our current study should be reassuring to couples who have conceived with fertility treatments and to those considering these methods', said Dr Edwina Yeung, lead author of the research which was conducted at the Eunice Kennedy Shriver National Institute of Child Health and Human Development in Maryland.
The study, published in the journal Fertility and Sterility, examined the differences in DNA methylation at birth and in early childhood (eight to ten years) in children born in New York State from 2008 to 2010. After analysing DNA methylation differences between 157 newborns conceived via IVF and 520 spontaneously conceived newborns, they observed decreased levels of DNA methylation at certain regions of DNA in newborns conceived via IVF. They did not observe any differences in DNA methylation in newborns conceived via intrauterine insemination (IUI) or ovulation induction (OI). These changes were specific to newborns conceived via IVF.
Follow-up DNA samples were obtained from 152 children between eight to ten years old and analysed for differences in DNA methylation between 23 children conceived via IVF, 34 children conceived via IUI/OI and children conceived without fertility treatment. They reported the lower levels in DNA methylation observed in newborns conceived via IVF did not persist in childhood with the exception of one region, in the GNAS gene located on chromosome 20, which gives rise to a variety of gene products. They also did not observe any differences in DNA methylation in children conceived via IUI or OI.
These findings suggest that further research needs to be carried out to determine how the techniques used in assisted reproduction technologies contribute to methylation differences observed at birth and in childhood.