Twice-Frozen Embryos Show Pregnancy, Live-Birth Rates Similar To Once-Frozen Embryos

Although twice-frozen embryos have a lower survival rate after thawing than once-frozen em bryos, they have similar pregnancy and equivalent live-birth rates, according to new research from Australia (Koch J, et al. Fertil Steril. 2011;96:58-62).

Researchers compared live-birth rates in twice-frozen embryo transfers and once-frozen embryo transfers generated from the same in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) treatment cycle, using data acquired retrospectively from the IVF Australia patient database. They identified infertile women who underwent IVF/ICSI and had embryos twice frozen between January 2003 and May 2009.

In total, 21,877 stimulation cycles resulted in a pregnancy rate of 32.2% per fresh transfer and 11,377 thaw cycles resulted in a pregnancy rate of 26.4% per embryo transfer. Of these, the twice-frozen embryos of 54 women achieved an 82% survival rate (55 embryos) and resulted in 52 embryo transfers in 44 women.

The researchers found that from the 40 once-frozen embryos transferred, there were 11 pregnancies, 6 live births, and 5 miscarriages. From the 52 twicefrozen em bryos, there were 13 pregnancies, 7 live births, and 6 miscarriages. The survival rate of twice-frozen embryos was lower than that of those frozen once (82% vs 89%; P = .012). The clinical pregnancy rates (25% vs 27.5%, respectively; P = .78) and livebirth rates (13% vs 15%, respectively; P = .83) were similar among twicefrozen and once-frozen embryo transfers