Perinatal outcome and postnatal health in children born from cryopreserved embryos

Abstract Frozen-thawed embryo transfer (FET) has been increasingly adopted as an adjunct to in vitro fertilization or intracytoplasmic sperm injection in recent years. It can reduce the risks of ovarian hyperstimulation syndrome and multiple pregnancies, and may even improve pregnancy outcomes in some subgroups such as patients with polycystic ovary syndrome. However, embryo cryopreservation may cause DNA damage, epigenetic changes, and alterations to gene expression profiles, and the potential impacts of cryopreservation on the embryos and on the long-term health of the resulting offspring are receiving increasing attention. Here, we aim to summarize the impact of cryopreservation on the embryos, perinatal outcomes, and long-term health of the offspring, hoping to explore the potential mechanisms and help guide the next steps in designing clinical studies. In this review, we found that there was no apparent difference in most perinatal outcomes between neonates born following FET and fresh embryo transfer, except for higher risks of large-for-gestational age and macrosomia in FET neonates. Studies on the long-term health and development of FET children are currently lacking; however, the limited evidence so far has found no risk of growth retardation, or chronic or malignant diseases. Large, well-designed, prospective studies taking full consideration of the confounding factors, including parental information, lifestyle, and environmental factors, are needed to confirm these conclusions.