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 dangerous complication called ovarian hyperstimulation syndrome. This condition can become fatal, and it may require pain medications, intravenous fluids, hospitalization and additional surgical procedures. Women with PCOS also have a greater risk of other pregnancy complications, including pregnancy loss, preeclampsia – high blood pressure during pregnancy, 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. Results appear today (Aug. 10) in the New England Journal of Medicine.
Using frozen embryos lowered the rate of ovarian hyperstimulation syndrome compared to using fresh embryos from 7.1 to 1.3 percent.
The group that received frozen embryos also had a higher frequency of live births—due to fewer pregnancy losses—and higher birth weights.
"Women with PCOS may have a higher chance of a successful pregnancy and may have less ovarian hyperstimulation when you electively freeze all the embryos and perform a frozen embryo transfer than if you do a fresh transfer," said Dr. Richard Legro, professor of obstetrics and gynecology and public health sciences at Penn State College of Medicine. "This protocol potentially offers immediate benefits to women with PCOS, so practitioners should consider freezing all embryos for these patients."
The use of hormones and medications to overstimulate the ovaries to release multiple eggs during in vitro fertilization is thought to create a potentially harmful environment for implantation, especially in women with PCOS, Legro said. Frozen embryo transfer allows a woman's ovary to recover from ovarian stimulation during in vitro fertilization and also gives time for her exposed endometrial lining to shed.
"By electing to freeze all the embryos, you create a healthy environment for the best embryos, as opposed to putting them back in a disturbed environment," Legro explained.
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. However, no patients developed severe preeclampsia pressure during pregnancy and the difference in neonatal death rates was not statistically significant. Both adverse outcomes need to be studied further, according to Legro, who led a team that hosted the Chinese collaborators at Penn State College of Medicine for five weeks as the group wrote the protocol for the multi-center trial and participated in regular steering committee meetings overseeing the trial.
Other researchers are Zi-Jiang Chen, Yuhua Shi, Daimin Wei, Jiayin Liu, Junhao Yan, Yingying Qin and Heping Zhang, all of Center for Reproductive Medicine, Shandong Provincial Hospital affiliated to Shandong University, Jinan, China; Yun Sun, Center for Reproductive Medicine, Ren Ji Hospital, School of Medicine, Shanghai, China; Bo Zhang, Center for Reproductive Medicine, Maternal and Child Health Hospital in Guangxi, China; Xiaoyan Liang, Center for Reproductive Medicine, Reproductive Medicine Center, the Sixth Affiliated Hospital of Sun Yat-sen University, Guangzhou, China; Yunxia Cao, Center for Reproductive Medicine, the First Affiliated Hospital of Anhui Medical University, Hefei, China; Jing Yang, Center for Reproductive Medicine, Wuhan University, China; Jing Li, Department of Obstetrics and Gynecology, First Affiliated Hospital of Nanjing Medical University, China; Ning Weng, Reproductive Medicine Center of Jinghua Hospital, Shenyang, China; Lifeng Tian, Center for Reproductive Medicine, Jiangxi Provincial Maternal and Child Health Hospital, Nanchang, China; Cuifang Hao, Center for Reproductive Medicine of Yantai Yuhuangding Hospital; Dongzi Yang, Center for Reproductive Medicine, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, China; Feng Zhou, Center for Reproductive Medicine, Department of Obstetrics and Gynecology, Sir Run Run Shaw Hospital affiliated to Zhejiang University School of Medicine, China; Juanzi Shi, Assisted Reproduction Center, Maternal and Child Health Care Hospital of Shanxi Province, China; Yongle Xu, Center for Reproduction and Genetics, Suzhou Municipal Hospital, Suzhou, China; and Han Zhao, Department of Biostatistics, Yale University School of Public Health.
The National Basic Research Program of China, State Key Program of National Natural Science Foundation of China, National Natural Science Foundation of China and Thousand Talents Program funded this research.
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