Subfertility Itself May Explain Poor Birth Outcomes

March 23, 2015

Assisted reproductive technology is often thought to account for the risk of low birth weight and preterm birth, but new research finds another factor plays a role.

Subfertility may account for the increased risk of low birth weights and preterm birth often attributed to the use of assisted reproductive technology (ART) procedures, a recently published study suggests.

Researchers at Boston University School of Public Health found that birth outcomes for babies whose mothers used ART were better in some cases, and worse in other circumstances, when compared with subfertile women who did not use ART.

The finding suggests that subfertility may be a distinct factor from ART in understanding the reasons behind the elevated risks in birth outcomes that are associated with in vitro fertilization and other ART procedures. However, the authors suggested a need to further refine how subfertile births are measured and to continue studying any independent risks that may be associated with women who experience fertility issues but ultimately are able to give birth.

For the study, the researchers looked at a total of 334,628 births and fetal deaths in Massachusetts between July 1, 2004, and December 31, 2008. The group was divided into three subgroups: those who required ART, subfertile women, and fertile women.

The risks of preterm birth and low birth weight were higher for singletons born to mothers who used ART than for those who had fertility problems but did not use ART. However, the risks of perinatal death were no higher for mothers who used ART than for fertile women, while the risks were significantly higher for singletons born to subfertile mothers who did not use ART.

When researchers dug into the singleton births some more, they found that the differences in rates of preterm birth and low birth weights were more pronounced when comparing the ART group to fertile women than to subfertile women, suggesting that underlying fertility problems may be an important factor.

For twins, the risk of death among pregnancies that involved ART were significantly lower than among either subfertile or fertile women.

The study is the first one published by a collaborative endeavor dubbed MOSART, for the Massachusetts Outcomes Study of Assisted Reproductive Technologies, and was published online last month in the journal Fertility and Sterility. MOSART is funded through a five-year grant from the National Institute of Child Health and Development.