Fetal development after assisted reproduction--a review

Despite the success of assisted reproduction technologies (ART) in allowing conception in couples with infertility problems, a growing body of evidence points to implication of ART on fetal birth weight alterations, fetal malformations, chromosomal aneuploidies and syndromes related to genomic imprinting modifications. Different causes can be accounted for to explain the increased risk of fetal defects. Pregnancies generated by ART differ from spontaneously achieved pregnancies in that gametes and embryos are cultured in vitro, more than one conceptus is transferred into the uterine cavity, and the time of transfer is different to what occurs in normal conditions. Epigenetic reprogramming of gene expression has been advocated in relation to the gamete and embryo manipulation, with a significant role of genomic imprinting in determining changes in fetal growth. Moreover, the maternal environment, with the ovarian hyperstimulation of the beginning of pregnancy, could alter the maternal response to the early phases of trophoblast invasion. There are suggestions that placental weights and placental/fetal weight ratios are increased in these pregnancies resembling the model of maternal undernutrition in the early phases of pregnancy. Therefore concern has also arisen around the possible long term and transgenerational effects of assisted reproduction procedures and studies should be carried out to evaluate these possibilities.