Use of frozen embryos may result in an increased risk of cancer for the child, according to the findings of a new Danish study.
In findings published this week in the Journal of the American Medical Association (JAMA), researchers indicate that children born from frozen embryos had more than double the risk of developing childhood cancers, including leukemia and sympathetic nervous system tumors.
Danish researchers studied nearly 1.1 million children born in Denmark between 1996 and 2012, using population based registry data and the Danish Infertility Cohort. The children’s data was linked to parental information.
Researchers examined fertility methods including using the fertility drug clomiphene, gonadotropin releasing hormone analogs, human chorionic gonadotropin, progesterone, and estrogen as well as assisted reproductive technologies including in vitro fertilization, intracytoplasmic sperm injection, and frozen embryo transfer.
Worldwide there is an increasing number of children born through the use of fertility treatments, including frozen embryo fertilization. Denmark has one of the highest rates of assisted reproductive technology. In 2018, nearly 10% of all children born in Denmark were conceived using fertility treatment.
Previous research has suggested children born using fertility treatments have an increased risk of health problems, and the children may be more likely to be premature and suffer some birth defects.
During the study period, a total of 2,217 children were diagnosed with cancer. Each fertility exposure was examined separately and compared to children born to fertile women to determine the cancer risk.
Children born with the use of frozen embryos faced a 2.5 fold increased risk of cancer compared to children born to fertile women. Roughly 44 per 100,000 children who were born from frozen embryos got cancer compared to 17 per 100,000 children who were born to fertile women.
There was no increased risk of cancer linked to other assisted reproductive technologies, including in vitro fertilization, intracytoplasmic sperm injection, or hormonal treatment. The risk was only seen in conjunction with frozen embryo use.
The researchers note that the study began in 1996, but protocols for freezing and fertilizing embryos have changed since then. Other factors were also not considered when determining cancer risk, including older parents and other health conditions of the parents. Those may play a factor in the increased cancer risk.
The study raises important questions regarding the safety of fertility treatments and the health of the child long-term, especially concerning the use of frozen embryos, the researchers determined. However, more research is needed to prove a cause and effect between the two, they said.