Vanishing twin linked to poor perinatal outcome.(News)

MONTREAL -- A history of a vanishing twin appears strongly associated with adverse perinatal outcomes in singletons born after in vitro fertilization, results of a retrospective cohort study suggest.

Contrary to previous findings, this research suggests that such adverse outcomes are seen even when the loss of the twin occurs early in the pregnancy.

"If further investigations support this finding, then it may push us even more urgently toward elective single-embryo transfer [SET] in the future," said Brooke Friedman, who is a fourth-year medical student at the University of California, San Francisco. She presented the research at the joint annual meeting of the American Society for Reproductive Medicine and the Canadian Fertility and Andrology Society.

According to data from 2000 (the most recent year for which such data are available), elective SET was performed in just 1.2% of IVF cycles in the United States.

Ms. Friedman and her coinvestigators hypothesized that singleton IVF pregnancies resulting from twin implantation more often have adverse outcomes because early placental development might be compromised. Such suboptimal placentation could affect later fetal growth and development, even after one of the fetuses is lost, she told this newspaper.

Other researchers also have speculated that the demise of a twin could create a toxic uterine environment for the surviving fetus.

The researchers in the current study analyzed data from 333 singleton births conceived through IVF/intracytoplasmic ...