Women who use in vitro fertilization (IVF) and other reproductive technologies may be more likely to have children with certain cancers or developmental delays than their peers who conceive the old-fashioned way, two new studies suggest.
The increased risk of complications may be due at least in part to advanced maternal age and other health factors that lead women to try assisted reproductive technology (ART) in the first place, say authors of both studies published today in Pediatrics. They also caution that the findings are too preliminary to deter women from trying to conceive this way.
"At this point in time, we don't believe the weight of the available evidence is strong enough to suggest that women should not proceed with ART," Melissa Bondy, an oncology researcher at Baylor College of Medicine in Houston who wrote an editorial accompanying the cancer study, said by email.
That's because the cancer study, like a lot of other research exploring the roots of birth defects and childhood disease, couldn't randomly assign some women to try ART just to see how their children turned out.
Instead, the researchers mined data from birth records for all children born in Norway between 1984 and 2011, pairing it with cancer registry data. The study included more than 1.6 million kids, including almost 26,000 conceived with ART.
Out of about 4,500 cancers, 51 occurred in ART-conceived children.
Overall cancer risk wasn't significantly greater for the ART kids, but the technology was linked to 67 percent higher odds of leukemia. It was also tied to nearly four times the risk of Hodgkin's lymphoma, though this was based on just three cases among the ART kids.
"Since some childhood cancers, such as leukemia, appear early in childhood, it is thought that factors related to early embryonic development or intrauterine environment may play a role," said lead author Dr. Marte Reigstad of the University of Oslo.
"What these factors are, we still know little about, but there are some indications that, for example, high parental age may play a part, as well as some rare hereditary genetic diseases," Reigstad added by email.
The second study examined another potential risk of ART - developmental delays - by looking at Massachusetts children enrolled in Early Intervention (EI), a program that serves infants and toddlers with disabilities.
Researchers linked birth records for more than 330,000 deliveries from 2004 to 2008 with data on more than 88,000 children referred to EI for services.
After excluding multiples, there were about 318,000 singleton births, including about 6,450 conceived with ART and another 5,500 born to couples that struggled to conceive.
Compared to offspring of couples without any fertility issues, ART-conceived babies were 27 percent more likely to get EI referrals, while infants born to so-called "subfertile" couples that struggled to conceive had 20 percent higher odds.
Because ART infants are more likely to arrive early and preemies may be more likely to enroll in EI programs, researchers adjusted the results to account for preterm deliveries.
"The results from our study suggest that prematurity is not the primary contributor through which ART is associated with EI enrollment," said lead author Dr. Hafsatou Diop of the Massachusetts Department of Public Health.
"While there is an increased risk, we don't necessarily think that it is enough to influence one's decision about whether or not to proceed with ART," Diop added by email.
Even though some risk may stem from factors like age or pre-existing medical conditions that women can't change, there's still plenty that women can do to lower the odds of pregnancy complications and resulting developmental delays no matter how their children are conceived, Diop noted.
"It is important to achieve and maintain optimal health prior to conception - this includes stopping smoking and drinking, reducing stress, maintaining a normal weight for height and eating well," Diop said.