Frozen Embryos May Be Best For IVF

http://abcnews.go.com/Health/wireStory?id=9866347

A new Finnish study suggests that women who use frozen embryos for in vitro fertilization are less likely to give birth prematurely, compared to women who use an egg that is removed, fertilized and implanted within the same cycle.

Researchers studied data from nearly 2,300 children conceived with frozen embryos, over 4,100 born after fresh embryos were used, and 32,000 pregnancies that did not require IVF or other fertility treatments.

From the group who used fresh embryos, about 1 in 11 of the babies were born prematurely, compared to about 1 in 16 from the group who used frozen embryos. Frozen embryos were also less likely to be linked to low birth weight and being small for the length of the pregnancy.

It is still unclear why frozen embryos result in a more favorable outcome. The freezing and thawing process may filter out "weak" embryos, leaving only the good quality ones. Frozen embryo transfer also allows doctors to time a woman's hormone cycle to more closely mimic natural conception.

The study's lead author, Dr. Sari Pelkonen, of Oulu University Hospital in Finland, said that considering effectiveness, price and safety, the best IVF option might be transferring one or two fresh embryos, ad freezing the rest for future implantation.