Delayed childbearing is a growing source of multiple births, study shows.
Starting in the 1980s, the number of multiple births—twins, triplets, quadruplets, and quintuplets—steadily increased from about 20 sets per 1,000 live births to almost 35 sets per 1,000 live births in the 2010s.
That trend presents some concerns, says Eli Adashi, MD, professor of medical science: multiple births come with various medical risks to both mother and babies, chief among them the risk of premature birth.
Adashi and Roee Gutman, PhD, an assistant professor of biostatistics at Brown’s School of Public Health, analyzed CDC birth data to determine how much of this surge in multiple births is the natural result of women choosing to have children later in life, as compared to assisted reproductive technologies, to which the phenomenon is most commonly attributed. Their results were published in the October issue of Obstetrics & Gynecology.
Adashi has a long history of analyzing the sources of multiple births. Until he met a colleague’s natural quadruplets, however, Adashi controlled for maternal age in his analyses but didn’t focus on the role that delayed childbearing may have on the boom of twin, triplet, and quadruplet births.
“Our question was: Does this social phenomenon of delayed childbearing have an impact on the incidence of multiple births in the United States?” Adashi says. “In the paper, we showed that yes, indeed, not all the multiple births out there have to do with fertility drugs or in vitro fertilization (IVF). There’s a sizable proportion of multiple births that are attributable simply to delaying childbearing. And the percentage of these spontaneous multiples seems to be growing.”
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