PROVIDENCE – The twin birth rate in the U.S. has surged over the last 30 years, mostly because of reproductive technologies including in vitro fertilization. Though it’s partly the cause, IVF could also be the most promising solution to reducing unintended twin births, argues Dr. Eli Adashi, a tenured professor of medical science at Brown University, in a new editorial in the American Journal of Obstetrics & Gynecology.
Twins typically live healthy lives, Adsashi said in a statement, but many serious medical complications of pregnancy and fetal development – such as preterm birth or low birth weight – are more common and difficult in twin pregnancies compared to single ones. For that reason, many physicians and public health officials consider technology’s artificial contribution to the soaring twin birth rate to be problematic. Meanwhile, many people who employ reproductive technologies aren’t necessarily trying to have twins; the technologies simply carry a greater risk of producing them.
“Sometimes nature makes it happen and there is nothing … you can … do about it,” said Adashi, former dean of medicine and biological sciences at Brown University and a professor of obstetrics and gynecology. “But in cases of IVF or other technologies, if you can avoid it, you often want to.”
Recent data from the Centers for Disease Control and Prevention indicate that the United States reached a record high twin birth rate of 33.9 per 1,000 live births in 2014. In the 17-year span before the ovulation-stimulating drug clomiphene citrate, or Clomid, was introduced in 1967, the twin birth rate had hovered around 20 per 1,000 live births. While more women are waiting until they are older to become pregnant, which increases the likelihood of twins, most of the climb to that record is because Clomid and IVF have become more common.
Clomid increases ovulation, meaning multiple eggs can sometimes become available for fertilization; in IVF, doctors often intentionally fertilize more than one egg in the lab and then implant those multiple embryos in a woman’s womb, in the hope that at least one will develop successfully. In recent years, doctors have cut the number of implantations to two in most cases, reducing the incidence of triplets and quadruplets, but increasing the rate of twin births.
IVF with one embryo
If cost weren’t a problem for would-be parents, the ideal case would be to implant just one embryo, Adashi said. In some states, including Rhode Island and Massachusetts, insurers not only cover much of the cost of IVF, but also often recommend skipping the Clomid/IUI step in favor of IVF with a single embryo transfer. In those cases, the likelihood of twins from Clomid is eliminated and successful IVF produces only a single birth. There are cases where Clomid-assisted ovulation, or “superovulation,” remains medically necessary, Adashi acknowledged, and in those cases it continues to occur.
But to reduce unintended twin births, states should consider requiring insurance coverage of single embryo transfer IVF, he said. “Combining a direct path to IVF with the judicious use of superovulation/IUI should go a long way toward curtailing the national twin birth rate.”
