An American study presented during the annual meeting of the American Society for Reproductive Medicine (ASRM) in San Diego (California), reveals that "the centers for medically assisted procreation (MAP) with a success rate lower than the national average transfer more embryos per cycle." This study, carried out by a team of researchers of the Yale University School of Medicine in New Haven (Connecticut), consisted of analysing "the data of all the American clinics that reported their activity to the Centers for Disease Control and Prevention (CDC) in 2008, a total of 436 centers."
The article points out that "this practice, which may be explained by the fact that these centers sought to increase their success rate by transferring more embryos, is however not linked to more multiple pregnancies, contrary to what might be thought." Thus "the less successful centers, defined as having lower average pregnancy rates per cycle with a standard deviation from the national average for the year in question, had pregnancy rates per cycle 38.2% lower among those under 35, 27.8% lower among patient aged 35-37, 20.6% lower among those aged 38-40 and 10.6% lower among those aged 41-42 " Moreover, the researchers point out that "these centers transferred more embryos per cycle among the youngest patients than the other centers," in the age groups of those under 35 and between 35 and 37. Lastly, "among all the age groups, the less successful centers did not have more multiple births than the others."