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Reference - N Engl J Med 2016 Aug 11;375(6):523 (level 1 [likely reliable] evidence)
- Polycystic ovary syndrome (PCOS) can cause infertility due to irregular or absent ovulations.
- In a randomized trial of 1,508 women with infertility and PCOS, in vitro fertilization (IVF) using cryopreserved embryos resulted in a higher rate of live births and lower risk of ovarian hyperstimulation syndrome compared to use of fresh embryos.
- The higher birth rate appears to be due to a lower rate of pregnancy loss.
The use of cryopreserved embryos is increasing as a means to secure potential future fertility and to decrease the risk of ovarian hyperstimulation syndrome in women undergoing IVF procedures. In addition, delayed transfer of cryopreserved embryos allows the endometrium a chance to recover after ovarian stimulating therapies, possibly resulting in increased pregnancy success rates (Fertil Steril 2016 Aug;106(2):251). Evidence from observational studies and trials support this, but these studies have not evaluated differences in live birth rates (Fertil Steril 2012 Aug;98(2):368-77.e1, Fertil Steril 2013 Jan;99(1):156). PCOS is often associated with infertility and women with PCOS having IVF may be at an even greater risk for ovarian hyperstimulation syndrome (Reprod Biomed Online 2009 Jul;19(1):8). A recent trial evaluated live birth rates in 1,508 women (mean age 28 years) with infertility and PCOS randomized to embryo cryopreservation and frozen embryo transfer vs. fresh embryo transfer during their first IVF cycle.
Frozen embryo transfer had higher live birth rates compared to fresh embryo transfer (49.3% vs. 42%, p = 0.004, NNT 14). The use of frozen embryos was also associated with lower incidence of moderate-to-severe ovarian hyperstimulation syndrome (based on symptoms and evidence of ascites) (1.3% vs. 7.1%, p < 0.001, NNT 18), but a higher incidence of preeclampsia (4.4% vs. 1.4%, p = 0.009, NNH 33). In terms of pregnancy rates, there were no significant differences between groups in the rate of biochemical pregnancy (human chorionic gonadotropin > 10 milliunits/mL) or clinical pregnancy (gestational sac on ultrasound), but there were significantly lower rates of biochemical pregnancy loss (22% vs. 32.7%, p < 0.001) and clinical pregnancy loss (14.6% vs. 25%, p < 0.001). Finally, no significant differences in rates of ectopic pregnancy, gestational hypertension, preterm delivery, stillbirth, or congenital anomalies between the two embryo transfer procedures were observed.
The results of the present trial demonstrate that frozen and fresh embryo transfer in women with PCOS yield similar clinical pregnancy rates, but the use of frozen embryos leads to a higher live birth rate. Taken together, these results suggest that the increased live birth rate with frozen embryos may not be due to higher rates of implantation, but may be due to differences in factors involved with maintaining pregnancy. The potential for bias was considered to be minimal due to the selection of the primary clinical outcome of live births and, although blinding was not used in the present study, the procedure for allocation concealment was judged to be adequate. The generalizability of the results of the present trial to women with infertility due to other causes, however, is unclear. In summary, the results of this trial suggest that using frozen embryo transfer improves IVF success in women with PCOS.
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