The use of assisted reproductive technologies (ART) has been increasing over the past three decades, and, in developed countries, ART account for 1-3% of annual births. In an attempt to compensate for inefficiencies in IVF procedures, patients undergo ovarian stimulation using high doses of exogenous gonadotrophins to allow retrieval of multiple oocytes in a single cycle. Although ovarian stimulation has an important role in ART, it may also have detrimental effects on oogenesis, embryo quality, endometrial receptivity and perinatal outcomes. In this review, we consider the evidence for these effects and address possible underlying mechanisms. We conclude that such mechanisms are still poorly understood, and further knowledge is needed in order to increase the safety of ovarian stimulation and to reduce potential effects on embryo development and implantation, which will ultimately be translated into increased pregnancy rates and healthy offspring.

These data suggest that both the developmental arrest of a significant proportion of mosaic embryos on Day 4, and the cell death or reduced proliferation of aneuploid cells within an embryo may be responsible for the observed decrease of aneuploid blastomeres from compaction to the peri-implantation stage.

In contrast to somatic cells, our results point to a specific role for Aurora C in the CPC during human preimplantation embryo development. Although, the presence of Aurora C in itself may not explain the high chromosome segregation error rate, the data presented here provide novel information regarding possible mechanisms.

Male-presumed fetal cells of haematopoietic and mesenchymal origin were identified in the appendix of all pregnant women who had sons. We suggest that fetal cells are present at sites of maternal tissue injury during pregnancy, and may participate in tissue repair.

This study was funded by the Portuguese Fundação para a Ciência e Tecnologia and the Netherlands Organization for Scientific Research. The authors have no conflicts of interest to declare.