In in vitro fertilization (IVF), the implantation of fresh embryos often results in children younger than the average. In contrast, the implantation of frozen embryos ends with children a little heavier than the average. A study suggests a possible cause. In vitro fertilization (IVF) acts on regions of genes that regulate embryonic growth. The effects would depend on genetic variations inherited from the parents.
Researchers at the University of Helsinki examined how IVF alters embryonic growth. They recruited 86 couples undergoing in vitro fertilization and 157 couples with natural pregnancies. They divided the first group into two subgroups: those who used fresh embryos and those who used frozen embryos.
In genetic analysis, scientists focused on the regulatory regions of two growth genes: IGF-2 and H19. Variations in these genes in parents have been associated with different epigenetic markers in children. The researchers then observed epigenetic markers in the placenta, dividing them into groups based on the genotype inherited from the parents.
At a later stage, the researchers compared data such as placental weight, birth weight, type of IVF procedure used, and inherited genotype. They noted that infants with a certain genotype and derived from the transfer of frozen embryos were much heavier than the average.
The observations are based on studies on prenatal alcohol exposure, for example. In fact, highlight how embryonic development is influenced by both genetics and environmental factors.