Differential Effects of Assisted Reproduction Technology on Placental Epigenetics and Angiogenesis: Insights from Fresh, Frozen, and Egg Donation Pregnancies

Background: The placenta plays a fundamental role in supporting fetal development, with angiogenesis being crucial for establishing an efficient maternal–fetal interface. Epigenetic mechanisms, particularly DNA methylation, can regulate the expression of angiogenesis-related genes and may be influenced by Assisted Reproductive Technology (ART), including In Vitro Fertilization (IVF) with fresh or frozen-thawed embryo transfer (ET and FET, respectively) and egg donation (ED), all potentially affecting placental vascular development and pregnancy outcomes. The present study compared global DNA methylation levels and the expression of Vascular Endothelial Growth Factor (VEGF), Placental Growth Factor (PlGF), and Soluble Fms-Like Tyrosine kinase-1 (sFlt-1) in placentae from physiological pregnancies obtained using ART versus those spontaneously conceived. Methods: Placental biopsies were collected from 98 physiological singleton term pregnancies (CTRL n = 29, ET n = 23, FET n = 25, ED n = 21). Global DNA methylation (5-mC) was quantified by ELISA Easy Kit; VEGF, PlGF, sFlt-1 mRNA and protein levels were assessed by Real-Time PCR and ELISA, respectively. Results: Global DNA methylation was significantly increased in FET and ED placentae compared with CTRL and ET. PlGF mRNA expression was upregulated in all ART groups, although protein levels were elevated only in ED placentae compared to CTRL and ET groups. VEGF mRNA was increased in FET placentae compared to CTRL, while protein levels showed a non-significant upward trend across ART groups. No differences in sFlt-1 expression were observed. Clinically, ART pregnancies were associated with significantly lower birth weight compared to CTRL, though values remained within the physiological range, and placental efficiency was preserved. Conclusions: Hypermethylation in FET and ED placentae may act as an epigenetic “buffer,” stabilizing vulnerable genomic regions and supporting the expression of pro-angiogenic factors. This adaptive mechanism likely helps to preserve placental function and fetal viability despite ART-related stressors, thereby mitigating the potential impact on birth weight.