Children born from frozen embryos twice as likely to develop cancer, particularly leukemia and neuroblastoma, says study
The risk is higher among women who use the frozen embryo transfer method -- the incidence being 44.4 per 100 000 -- which is more than two-fold higher than children born to fertile women
Children born through in vitro fertilization, involving frozen embryos, have a higher risk of developing childhood cancer than children born to fertile women, finds a new study.
The study was carried out in Denmark, where fertility treatment is popular. Children conceived through frozen embryo transfer had more than twice the risk of developing childhood cancer, particularly leukemia and neuroblastoma, according to the team of Demark scientists, who looked at cancer rates among these children.
Maternal infertility and other fertility techniques, including fertility drugs, do not put children at higher risk for these cancers, says the study carried out by Dr. Marie Hargreave from Danish Cancer Society Research Center, and her team.
According to experts, it is known that children born after the use of fertility treatment are born earlier and lighter. They are also likely to inherit medical conditions at or before birth. But the long-term health risks of such fertility treatments are not well-established, note scientists.
To evaluate the risks posed by different fertility treatments, the team of scientists analyzed data from the Danish Medical Birth Register, the Danish Cancer Registry, and the Danish Infertility Cohort.
Through these databases, they collected information on 1,085,172 children, born in Denmark, between January 1996 and December 31, 2012. Of these children, 2,217 had cancer. The team also studied cancer rates among children born to fertile women, for comparison.
Their results showed that the rate of childhood cancer among children born to women was 17.5 per 100 000. On the other hand, the rate was higher among women who used the frozen embryo transfer method -- the incidence being 44.4 per 100 000 -- which is more than a two-fold increase.
The scientists think that certain drugs used during the frozen embryo treatment may have something to do with the increased cancer risk. "Frozen embryo transfer is the only procedure in Denmark (excluding fresh egg donation) in which estrogen, an established carcinogen, is part of the treatment protocol, and progesterone, a drug classified as “reasonably anticipated to be a human carcinogen, is used approximately 10 weeks into pregnancy," says the study. Although, in this study, the team found no increased risk when either hormonal fertility drugs were used. But, they add, the duration or timing of exposure may raise the risk.
However, the team cautions that their study could have limitations. Because childhood cancers are so rare, statistical tools may limit the accuracy of the results, they add.
With frozen embryo transfers becoming more and more common, it will be important to see more studies on this topic, Dr. Sunita Katari, an assistant professor at the Magee Center for Fertility & Reproductive Endocrinology at the UPMC Magee-Womens Hospital in Pittsburgh, Pennsylvania told Reuters. “It’s something that really needs more investigation and larger studies from different countries,” she explains.
Parents shouldn't worry, Dr. Jeffrey Goldberg, an OB-GYN and reproductive endocrinologist at Cleveland Clinic A Goldberg, who was not involved in the study, told CNN. He adds, "A 2.4 fold increase is clinically significant, but these are very small numbers, and this is based on older data going back to '96 and some of the things here may not be applicable now. I wouldn't want this to set off alarm bells."
The study has been published in JAMA.