Assisted reproductive technologies (ART) are associated with several complications including low birth weight, abnormal placentation and increased risk for rare imprinting disorders. Indeed, experimental studies demonstrate ART procedures independent of existing infertility induce epigenetic perturbations in the embryo and extraembryonic tissues. To test the hypothesis that these epigenetic perturbations persist and result in adverse outcomes at term, we assessed placental morphology and methylation profiles in E18.5 mouse concepti generated by in vitro fertilization (IVF) in two different genetic backgrounds. We also examined embryo transfer (ET) and superovulation procedures to ascertain if they contribute to developmental and epigenetic effects. Increased placental weight and reduced fetal-to-placental weight ratio were observed in all ART groups when compared with naturally conceived controls, demonstrating that non-surgical embryo transfer alone can impact placental development. Furthermore, superovulation further induced overgrowth of the placental junctional zone. Embryo transfer and superovulation defects were limited to these morphological changes, as we did not observe any differences in epigenetic profiles. IVF placentae, however, displayed hypomethylation of imprinting control regions of select imprinted genes and a global reduction in DNA methylation levels. Although we did not detect significant differences in DNA methylation in fetal brain or liver samples, rare IVF concepti displayed very low methylation and abnormal gene expression from the normally repressed allele. Our findings suggest that individual ART procedures cumulatively increase placental morphological abnormalities and epigenetic perturbations, potentially causing adverse neonatal and long-term health outcomes in offspring.

Epidemiologic studies have shown an increased rate of adverse perinatal outcomes, including small for gestational age (SGA) births, in fresh in vitro fertilization (IVF) cycles compared with frozen embryo transfer cycles. This increase is not seen in the donor oocyte population, suggesting that it is the peri-implantation environment created after superovulation that is responsible for these changes. During a fresh IVF cycle, multiple corpora lutea secrete high levels of hormones and other factors that can affect the endometrium and the implanting embryo. In this review, we discuss both animal and human data demonstrating that superovulation has significant effects on the endometrium and embryo. Additionally, potential mechanisms for the adverse effects of gonadotropin stimulation on implantation and placental development are proposed. We think that these data, along with the growing body of epidemiologic evidence, support the proposal that frozen embryo transfer should be considered preferentially, particularly in high responders, as a means to potentially decrease at least some of the adverse perinatal outcomes associated with IVF.

Aims/hypothesis Maternal obesity is associated with an increased risk of obesity and impaired glucose homeostasis in offspring. However, it is not known whether a gestational or pre-gestational exposure confers similar risks, and if so, what the underlying mechanisms are. Methods We used reciprocal two-cell embryo transfers between mice fed either a control or high-fat diet (HFD) starting at the time of weaning. Gene expression in placenta was assessed by microarray analyses. Results A pre-gestational exposure to a maternal HFD (HFD/control) impaired fetal and placental growth despite a normal gestational milieu. Expression of imprinted genes and genes regulating vasculogenesis and lipid metabolism was markedly altered in placenta of HFD/control. An exposure to an HFD (control/HFD) only during gestation also resulted in fetal growth restriction and decreased placental weight. Interestingly, only a gestational exposure to an HFD (control/HFD) resulted in obesity and impaired glucose tolerance in adulthood. Conclusions/interpretation An HFD during pregnancy has profound consequences for the offspring later in life. Our data demonstrate that the mechanism underlying this phenomenon is not related to placental dysfunction, intrauterine growth restriction or postnatal weight gain, but rather an inability of the progeny to adapt to the abnormal gestational milieu of an HFD. Thus, the ability to adapt to an adverse intrauterine environment is conferred prior to pregnancy and it is possible that the effects of a maternal HFD may be transmitted to subsequent generations.

BackgroundWe, and others, have demonstrated previously that there are differences in DNA methylation and transcript levels of a number of genes in cord blood and placenta between children conceived using assisted reproductive technologies (ART) and children conceived in vivo. The source of these differences (the effect of ART versus the underlying infertility) has never been determined in humans. In this study, we have attempted to resolve this issue by comparing placental DNA methylation levels at 37 CpG sites in 16 previously identified candidate genes in independent populations of children conceived in vivo (‘fertile control’ group) with ART children conceived from two groups: either autologous oocytes with infertility in one or both parents (‘infertile ART’ group) or donor oocytes (obtained from young fertile donors) without male infertility (‘donor oocyte ART’ group).ResultsOf the 37 CpG sites analyzed, significant differences between the three groups were found in 11 CpGs (29.73 %), using ANOVA. Tukey’s post hoc test on the significant results indicated that seven (63.63 %) of these differences were significant between the donor oocyte ART and fertile control groups. In addition, 20 of the 37 CpGs analyzed had been identified as differentially methylated between ART and fertile control groups in an independent population in a prior study. Of these 20 CpG sites, 9 also showed significant differences in the present population. An additional 9 CpGs were found to be significantly different between the two groups. Of these 18 candidate CpGs, 12 CpGs (in seven candidate genes) also showed significant differences in placental DNA methylation levels between the donor oocyte ART and fertile control groups.ConclusionsThese data suggest strongly that the DNA methylation differences observed between ART and in vivo conceptions are associated with some aspect of ART protocols, not simply the underlying infertility.Electronic supplementary materialThe online version of this article (doi:10.1186/s13148-015-0071-7) contains supplementary material, which is available to authorized users.

Most IVF-conceived children are healthy, but IVF has also been associated with adverse obstetric and perinatal outcomes as well as congenital anomalies. There is also literature suggesting an association between IVF and neurodevelopmental disorders as well as potentially long-term metabolic outcomes. The main driver for adverse outcomes is the higher risk of multiple gestations in IVF, but as the field moves toward single embryo transfer, the rate of multiple gestations is decreasing. Studies have shown that singleton IVF pregnancies still have a higher incidence of adverse outcomes compared to unassisted singleton pregnancies. Infertility itself may be an independent risk factor. Animal models suggest that epigenetic changes in genes involved in growth and development are altered in IVF during the hormonal stimulation and embryo culture. Further animal research and prospective human data is needed to elucidate the mechanisms by which IVF may contribute to adverse outcomes and to decrease risks.