Health of Offspring Following Cryopreservation of Oocytes and Embryos

In this chapter, we summarize the risks in pregnancies after frozen/thawed oocyte and embryo cryopreservation. Further short- and long-term health risks in children born after oocyte and embryo cryopreservation are described. Women pregnant after frozen embryo transfer have an increased risk of hypertensive disorders in pregnancy including preeclampsia compared with fresh cycles. Moreover, the risks of hypertensive disorders in pregnancy seem to increase further in programmed frozen cycles compared to natural frozen cycles. Further on children born after frozen thawed embryo transfer have a lower risk of preterm birth and low birth weight than children born after fresh embryo transfer but a higher risk than spontaneously conceived children. The higher risk of macrosomia and large for gestational age in children born after frozen thawed embryo transfer compared to fresh embryo transfer and spontaneous conception may have a negative effect on long-term health. However, studies so far have been inconclusive. Vitrification might damage the eggs, which may pose health risks for the offspring. Information collected so far at birth and up to the age of 6 years has shown no short- or long-term health differences between children born after use of frozen and non-frozen (or fresh) oocytes though this needs to be followed with larger scale studies.