For the last decade there have been... let's call them rumors... about children born from reproductive technologies, specifically that these kids had a greater risk of developing cancer than those conceived normally. But according to a new study, would-be moms and dads to children born via assisted reproductive technology (ART) can breathe a little easier.
The study, titled “Risk of cancer in children and young adults conceived by assisted reproductive technology,” was published in the February issue of the European Society of Human Reproduction and Embryology’s journal, Human Reproduction, and concluded that children born after ART do not appear to be at greater risk of developing cancer than other children. Past studies offered conflicting evidence on the issue, so researchers from The Netherlands Cancer Institute, Amsterdam, delved deeper, following the children in the study for an average of 21 years, making this the first study to compare outcomes over an extended period of time. The longer time period means the study offers a more comprehensive analysis on the longer-term effects of ART in regards to cancer development.
While the study concludes that children born after ART are not at a greater risk for developing cancer than other kids, researchers do acknowledge that there could be a slightly increased risk in specific cases, though not in a way that’s statistically significant. The minor elevated risk was seen in two scenarios: children conceived after intracytoplasmic sperm injection, which involves injecting a single live sperm directly into the center of an egg, and children conceived from embryos that had been frozen before being thawed and used for fertility treatment. “These are two types of fertility treatments that are used more often nowadays,” said the study’s first author, Mandy Spaan, “We also found a slightly increased, statistically insignificant risk of lymphoblastic leukaemia and melanoma. As the numbers of cancers in these groups were small, these findings may be due to chance and must be interpreted with caution." In other words, while the risk of developing these types of cancers appears to be slightly increased in children born via ART, the uptick was so minimal, it may have been coincidental. So until further investigation confirms the findings, would-be parents shouldn’t consider it fact.
For the study, researchers examined data on more than 47,690 kids, and found that 231 went on to develop cancer after birth. After adjusting for factors that could confound the results, such as their age and the cause of their parents’ subfertility (that's a reduced period of time without desired conception), the researchers found that the overall long-term risk for cancer was neither increased in the ART-conceived children compared with naturally conceived children from subfertile women, nor when compared with the general population.
The data originated from a nationwide study of subfertile women treated in one of 12 Dutch fertility clinics between 1980 and 2001. Researchers then linked that data to numbers on the incidences of cancer from The Netherlands Cancer Registry between January 1989 and November 2016. They also collected Information from the mothers’ questionnaires and medical records including the method of conception and any confounding factors (like the cause of the parents' subfertility, the mother's age, the child's birth year, birth weight, duration of pregnancy, and whether they were single or multiple births).
“This study, with a median follow-up of 21 years, is especially important because it includes a comparison group of naturally conceived children born to subfertile women; these women are different from the general population and it is possible that difficulty in conceiving could be a factor that influences the risk of cancer in their offspring," said lead researcher, Professor Flora van Leeuwen, Head of the Department of Epidemiology in The Netherlands Cancer Institute, Amsterdam. That means that if parents with fertility issues do have children via ART and those children are found to have a slightly higher risk of developing cancer, the connection could be due to an underlying genetic cause tied to the parents’ subfertility; not the fertility treatments themselves. For now, scientists can’t say for sure what the root of any slight increased risk is, but it’s looking unlikely that ART is responsible. “These results provide reassuring evidence that children conceived as a result of fertility treatments do not have an increased risk of cancer after a median follow-up of 21 years. They will enable physicians to better inform couples considering fertility treatment about its long-term safety for their children.”
However, because more children are being born through ICSI and cryopreservation of embryos, researchers want to further investigate the long-term cancer risk in larger numbers of children born as a result of these techniques. "We are currently expanding our study to include more than 30,000 ART-conceived children born in more recent years,” van Leeuwen said. “It will include children born after ICSI and/or embryo cryopreservation of the embryo. We hope this will provide more evidence about the possible long-term risk of cancer for these children."
While the newest study has some potential limitations — the small number of cancers makes it difficult to produce reliable results in a subgroup analysis and the method of conception couldn’t be identified in 12% of children from the information in the mothers' questionnaires and medical records —it also has some notable strengths. The large sample size and long, extensive follow-up, comparison with a variety of populations, and detailed information on potential confounding factors make the study uniquely comprehensive, according to experts.
“Assisted reproduction still feels unnatural to some people, and there have been persistent concerns about the effects on a baby's future health when their life began with technical assistance,” says Kate White, MD, MPH, assistant professor of obstetrics and gynecology at Boston University. “Studies like this one give more reassurance to worried parents that their child will grow up as healthy as any other, even if they needed help to become pregnant.”
Overall, it’s important to remember that cancer in children and young adults is rare. So no matter how your child is conceived, the risk is low — in fact, childhood cancers account for just one percent of all cancers diagnosed each year. And while experts still don’t know the exact causes of childhood cancers, it may be important to discuss risk factors with your doctor before you conceive, and be aware of any signs and symptoms associated with various childhood cancers.