Most women who do IVF are impregnated with a fresh embryo. However, a new study suggests that using a previously frozen and then thawed embryo may have a better success rate. In a randomized trial of 1,508 women undergoing IVF for the first time, the researchers found that 49.3% of those who used frozen embryos gave birth to a baby, compared with 42% of those who used fresh embryos. The work, led by Dr. Zi-Jiang Chen of the center for reproductive medicine at Shandong Provincial Hospital in China, was published Wednesday in the New England Journal of Medicine. The new study is one of the largest yet to look at the difference between using fresh embryos and frozen embryos in IVF. The data were collected from fourteen medical centers throughout China from 2013 to 2015, and all participants were followed throughout the duration of their pregnancy. The authors found little difference in pregnancy rates among women who used fresh embryos and those who used frozen ones. However, they did see a significant difference in how likely these women were to stay pregnant. Nearly 33% of women who had a fresh embryo transfer lost the baby over the course of their pregnancy, compared with 22% of those who were implanted with a frozen embryo. Frozen embryos were also associated with a higher birth weight in babies. http://www.latimes.com/science/sciencenow/la-sci-sn-ivf-frozen-embryos-20160809-snap-story.html
