The study was published online by the journal Pediatrics on Monday and will be published in the August print issue.
Dr. Bengt Källén at the University of Lund and colleagues in Linköping and Stockholm noted that earlier studies showed the risk cancer among children born after IVF was not higher than among other children.
However, they pointed out that test-tube infants are often born prematurely and have breathing problems at birth. In addition, researchers emphasised that the reason behind the slight increased risk probably did not have to do with IVF.
“We found a moderately increased risk for cancer in children who were conceived by IVF,” the researchers wrote. “This is probably not attributable to the IVF procedure itself. It should be stressed that the individual risk for a child who is born after IVF to develop childhood cancer is low.”
The researchers followed 26,692 children who were born in Sweden after IVF from 1982 to 2005. Using the Swedish Cancer Register, they compared those who had cancer and compared them with those who had cancer who were not conceived by IVF.
Consequently, they identified 53 cases of cancer in children who were born after IVF against 38 expected cases in non-IVF children. Maternal age, weight, smoking, subfertility, previous miscarriage, body mass index and multiple births did not sigificantly affect cancer risk in offspring.
However, high birth weight, premature delivery, breathing problems and a low Apgar score, a method to quickly assess the health of a newborn immediately, had higher rates of cancer.
Blood cancers were the most common, affecting 18 children compared with the expected 12, of which 15 were acute lymphoblastic leukaemia. They were followed by 15 affecting the central nervous system compared with the expected eight, of which seven were brain tumours.
In addition, there were six cases of a rare white blood cell disorder called histiocytosis against one expected and two cases of eye tumours, double the expected number.
Two of the IVF children who developed cancer had Down syndrome. Children with Down syndrome are at an increased risk of cancer, particularly childhood leukaemia.
The researchers acknowledged more studies on larger populations are necessary.
“Additional studies on large populations are needed to permit analysis of such a rare outcome as cancer and notably of specific types,” they wrote.