By Lisa Rapaport

(Reuters Health) – Women who struggle to get pregnant or use reproductive technologies like in vitro fertilization (IVF) may be more likely to have preemies and kids with birth defects than their peers who conceive without difficulty, a U.S. study suggests.

Infertility has long been linked to an increased risk of premature deliveries, and the current study offered fresh evidence of this. Compared to women without any fertility issues, women who struggled to conceive were 39 percent more likely to have premature babies, while the increased risk associated with using reproductive technologies was 79 percent.

The study also found women who were “subfertile,” or struggled to conceive, were 21 percent more likely to have babies with birth defects than women who got pregnant without difficulty.

In addition, when researchers accounted for how early in pregnancy babies arrived, they found infants born to mothers with fertility issues or women who used ART were more likely to have congenital abnormalities, cardiovascular conditions, infectious diseases and respiratory problems.

“We think that medical conditions of the mother related to the subfertility are major drivers of adverse outcomes,” said senior study author Judy Stern of Dartmouth-Hitchcock in Lebanon, New Hampshire.

“It’s important to remember that the magnitude of any increase in risk is very small,” Stern said by email. “We are not talking about major differences in rates of disease conditions.”

Pregnancy normally lasts about 40 weeks, and babies born after 37 weeks are considered full term.

In the weeks immediately after birth, preemies often have difficulty breathing and digesting food. They can also encounter longer-term challenges such as impaired vision, hearing and cognitive skills, as well as social and behavioral problems.

For the study, researchers examined data on 336,705 infants born to fertile mothers in Massachusetts from 2004 to 2010, as well as 5,043 babies born to women with fertility problems and 8,375 infants whose mothers conceived using ART.

For some of the earliest preemies in the study, born from 28 to 33 weeks gestation, babies born using ART had a lower risk of birth defects than infants born to women with fertility problems who didn’t use ART, researchers report in Pediatrics.

Women’s fertility status or use of ART, however, didn’t appear to influence the risk that babies would be underweight, develop neurological or blood disorders, or die as newborns.

The study wasn’t a controlled experiment designed to prove whether or how fertility problems or ART might directly cause birth defects or certain diseases in babies. Another limitation is that researchers lacked data on some aspects of women’s health records and any fertility treatments that might impact the chance of babies having certain birth defects or health issues, the authors note.

Regardless of whether babies were born naturally or using ART, the vast majority were healthy, noted Logan Spector, a researcher at the University of Minnesota Medical School who wasn’t involved in the study.

“There has been a large a large amount of research showing that babies conceived by ART are smaller, have shorter gestations, and more birth defects than babies conceived naturally,” Spector said by email.

“However, a common drawback to these studies has been the difficulty of separating ART treatments from the underlying cause of infertility,” Spector added. “What this study adds is the finding that the health risks of infants born to subfertile mothers and those who had ART treatment are substantially similar, suggesting that subfertility is the common factor.”

SOURCE: Pediatrics, online July 3, 2018.