Researchers analyzed data from more than 1 million children born in Denmark between 1996 and 2012. They found that the rate of childhood cancer was 44.4 per 100,000 for children born using frozen embryo transfer, compared with 17.5 per 100,000 for children born to fertile women, CNN reported.
There wasn't an increased cancer risk among children born to parents who used other types of assisted reproductive technology such as fertility drugs, IVF or intracytoplasmic sperm injection.
The study was published Tuesday in the Journal of the American Medical Association.
The findings are "interesting and of potential concern, but you have to look at this study in perspective," Dr. Jeffrey Goldberg, a reproductive endocrinologist at Cleveland Clinic who was not involved with the study, told CNN.
"Fortunately, child cancers are pretty rare," and parents shouldn't worry about these findings, he said.
"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," Goldberg told CNN. "I wouldn't want this to set off alarm bells."