Transfer of Cryopreserved Embryos: Does It Increase Risk of Malformations?

In one of the largest studies to date to address the issue of whether reproductive technologies increase the risk of birth defects researchers came to the conclusion that the transfer of cryopreserved embryos does not increase the risk of birth defects. This research was published in the New England Journal of Medicine May 05, 2012.

Researchers in Australia studied birth defects in over 300,000 women which included 308,974 births, 6,163 of which had resulted from assisted reproductive technologies.

This study continued to support the long held understanding that women simply with a history of infertility have a small, but significant increase in birth defects.

Children who were conceived from the transfer of cryopreserved embryos did not exhibit any increased risk of malformations.

This lack of increase in malformations was true whether the oocytes were fertilized via standard insemination (allowing the sperm to enter the egg via normal fertilization processes) or via Intracytoplasmic Sperm Injection (ICSI), where a normal appearing sperm is injected into the oocyte. This was somewhat surprising as offspring following ICSI and fresh embryo transfer was found to be associated with a small but significant increase in malformations. It is hypothesized that the decrease in malformations from cryo cycles may be due to the belief that abnormal embryos have a lower chance of surviving a freeze and then thaw

Previous studies have revealed a lack of increased malformations following transfer of cryopreserved embryos; in fact some studies have shown a slight decrease in malformations in children conceived with thawed frozen embryos. This decrease in malformations was not seen but no increase in malformations was observed in all categories of cryopreserved embryo transfer cycles.

This study is further evidence of the safety of transferring embryos which were previously cryopreserved. See the full study here.

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