1. Frozen-embryo transfer was associated with a significantly lower frequency of pregnancy loss and ovarian hyperstimulation compared to fresh-embryo transfer in women with polycystic ovary syndrome (PCOS) receiving in vitro fertilization (IVF) treatment.
2. Frozen-embryo transfer was associated with a significantly higher risk of preeclampsia compared to fresh-embryo transfer in this demographic.
Evidence Rating Level: 1 (Excellent)
Study Rundown: In IVF treatment the transfer of fresh embryos, when available, is the usual practice. However, IVF has been shown to be associated with greater risks of maternal and neonatal complications, including preeclampsia, preterm delivery, low birth weight, and congenital anomalies compared to spontaneous pregnancies. Studies have shown that women with PCOS that are receiving IVF treatment are at increased risk of complications later in the pregnancy. The transfer of fresh embryos is the usual practice in most IVF units but studies have shown that frozen embryo transfer is associated with lower risk of preterm birth, low birth weight, and perinatal death than were pregnancies from fresh-embryo transfer. This study investigated whether there was a difference between fresh vs. frozen-embryo transfer in women with PCOS and live birth outcomes. The women randomly received either fresh or frozen embryos. Among PCOS women receiving IVF treatment frozen-embryo transfer was associated with a higher rate of live birth, a lower risk of ovarian hyperstimulation syndrome and a higher risk of preeclampsia compared to fresh-embryo transfer. There were no significant differences between the groups in regards to neonatal complications.
Click to read the study, published today in NEJM
Relevant Reading: Obstetric and perinatal outcomes in singleton pregnancies resulting from the transfer of frozen thawed versus fresh embryos generated through in vitro fertilization treatment: a systematic review and meta-analysis
In-Depth [randomized controlled trial]: This was a multicenter, randomized, controlled trial and included a total of 1508 infertile women with PCOS. Women randomly received either fresh-embryo transfer or frozen-embryo transfer. The primary outcome was a live birth after the first embryo transfer. There was a significantly higher frequency of live birth in the frozen-embryo transfer compared to the fresh-embryo transfer (49.3% vs. 42.0%; RR 1.17, 95%CI 1.05-1.31; p = 0.004). There was also a significantly lower frequency of pregnancy loss (22.0% vs. 32.7%; RR 0.67, 95%CI 0.54-0.83; p < 0.001) and ovarian hyperstimulation syndrome (1.3% vs. 7.1%; RR 0.19; 95%CI 1.26-7.73; p = 0.009) in the frozen-embryo transfer compared to the fresh-embryo group. However, there was a significantly higher frequency of preeclampsia in the frozen-embryo transfer compared to the fresh-embryo transfer (4.4% vs. 1.4%; RR 3.12; 95%CI 1.26-7.73; p = 0.009). There were no between group differences in regards to pregnancy and neonatal complications. Overall, there were two stillbirths and five neonatal deaths in the frozen-embryo group and none in the fresh embryo group (analyses did not reach significance). The study was limited by 10% of the patients deviating from the protocol and that the study was only limited to women with PCOS.