The fewer babies a pregnant woman carries, the more likely she is to bring a healthy one home from the hospital, suggests a new study. The findings may prompt a woman bearing identical twins plus one or more additional fetuses, a relatively common scenario after in vitro fertilization (IVF), to consider removing the risky twin pair in order to save the solo siblings, researchers say. “Singletons are always our goal,” lead researcher Dr. Alan Copperman, director of reproductive endocrinology at Mount Sinai School of Medicine in New York, told Reuters Health. “We know that twins do better than triplets, and we know that singletons do better than twins.” Due to the embryo split that defines identical twins, he explained, one of the pair may receive less blood flow than its brother or sister. This can lead to a greater chance of premature delivery, developmental abnormalities and even death. Add another fetus, and there is even less to go around and more chances for problems. While earlier studies have tracked the rate of identical twins from pregnancies after assisted reproduction to more than double that of natural conceptions, information on outcomes has been lacking. “We were too often forced to rely on anecdotal experience in making recommendations to our patients,” noted Copperman. This inspired he and colleagues to delve into a dataset of nearly 3,500 pregnancies conceived by IVF between 2002 and 2008. About 72 of the pregnancies (about 2 percent) included identical twins, and about half of these women carried at least one additional fetus. In almost a third of the pregnancies, identical twins were completely aborted by the woman’s body. Another 4 percent were naturally reduced to just one fetus. If neither occurred spontaneously within the first trimester, most of the women with three or more fetuses had her identical twins surgically aborted. Every one of these women subsequently gave birth to at least one healthy baby.

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