WASHINGTON, Aug. 10 (Xinhua) -- For women with polycystic ovary syndrome (PCOS) who turn to in vitro fertilization to conceive children, frozen embryos may be a better and safer choice than fresh, a study said Wednesday.
PCOS is a hormonal disorder that affects up to 10 percent of women of childbearing age. When women with PCOS undergo in vitro fertilization, they have an increased risk of a potentially life-threatening complication called ovarian hyperstimulation syndrome.
Women with PCOS also have a greater risk of other pregnancy complications, including pregnancy loss, preeclampsia, preterm delivery, low birth weight and birth defects.
Although fresh embryos have been preferred for in vitro fertilization, previous research has suggested that frozen embryos could improve the rate of live births and lower the rates of ovarian hyperstimulation syndrome and pregnancy complications in women with PCOS.
In the new study, which took place at several reproductive medical centers throughout China, 1,508 infertile women with PCOS were randomized to receive either fresh embryos or frozen embryos during their first in vitro fertilization cycle.
Using frozen embryos lowered the rate of ovarian hyperstimulation syndrome compared to using fresh embryos from 7.1 to 1.3 percent, said the study appearing in the New England Journal of Medicine.
The group that received frozen embryos also had a higher frequency of live births -- due to fewer pregnancy losses -- and higher birth weights.
"We found that for women with PCOS, using embryos that have been frozen and thawed can get better clinical results than doing a traditional fresh embryo transfer," study co-author Heping Zhang, professor of Yale University, said in an email.
"This protocol potentially offers immediate benefits to women with PCOS, so practitioners should consider freezing all embryos for these patients," study co-author Richard Legro, professor of the Penn State University, added in a statement.
Frozen embryo transfer allows a woman's ovary to recover from potentially harmful ovarian stimulation during in vitro fertilization and also gives time for her exposed endometrial lining to shed, they said.
However, frozen embryo transfer was also associated with higher rates of two negative outcomes compared to fresh embryo transfer, the researchers reported.
Preeclampsia and neonatal death were more common in the frozen embryo transfer group, but the good news was that no patients developed severe preeclampsia pressure during pregnancy and the difference in neonatal death rates was not statistically significant.