TUESDAY, May 29 (HealthDay News) -- The rate of monozygotic twinning after blastocyst transfer has improved since 2002 and is now similar to the rate observed after cleavage stage transfer, researchers report in the May issue of Fertility and Sterility.
Amin A. Milki, M.D., and colleagues from Stanford University Medical Center in Stanford, Calif., compared the incidence of monozygotic twinning after day-three embryo transfer and blastocyst transfer in 932 pregnancies conceived between 2002 and 2005, and 554 pregnancies conceived before 2002.
The researchers found that the rate of twinning for the more recent period was 2.3 percent for blastocyst transfer and 1.8 percent for embryo transfer. In contrast, the rate for blastocyst transfer was 5.6 percent before 2002.
"Our study suggests that the risk of monozygotic twinning with blastocyst transfer is significantly lower in the more recent time period and is in the range of what is seen with cleavage stage transfer," Milki and colleagues conclude. "It is likely that improvements in culture systems as experience is gained with blastocyst transfer played a role."
Abstract
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