The increased risk for rare childhood tumors seen in the U.K. study and in the CoNARTaS study could even be down to chance as the numbers used in the analyses are relatively small.
"When we subdivide by cancer types, our numbers get smaller and smaller, and therefore the role of chance is increased," Dr. Williams commented. "The answer is to keep studying this area, perhaps do another systematic review, putting all of the results together, and then we will have more reliable findings."
Dr. Williams added: "So far, it looks like the results are really positive for the many children born after assisted conception."
Cancer Research U.K. funded the U.K. study. The U.K. National Institute of Health Research provided funding to Dr. Williams. CoNARTaS is supported by ESHRE, Sahlgrenska University Hospital, the University of Copenhagen, the Danish Agency for Science Technology and Innovation, and the Nordic Federation of Societies of Obstetrics and Gynecology. Dr. Williams and Dr. Pinborg said they had no relevant financial disclosures.