Fresh embryo transfer may yield higher rates of success for women with low prognosis for in vitro fertilization

1. In this randomized controlled trial, the fresh embryo transfer group had a higher rate of live births compared to the frozen embryo transfer group, in women with a low prognosis of a successful pregnancy using in vitro fertilization (IVF). 

Evidence Rating Level: 1 (Excellent) 

In vitro fertilization (IVF) has progressed bounds since first being introduced, however, many women are still struggling. Specifically, women with 9 or fewer oocytes retrieved, or those with poor ovarian reserve (defined as antral follicle count <5 or serum anti-Müllerian hormone level <8.6 pmol/L) are considered to have poor prognosis for successful IVF.  To give themselves a better chance of a successful pregnancy, many people have adopted embryo conservation through elective freezing of all embryos then a planned frozen embryo transfer. Although previous studies have shown evidence for frozen versus fresh embryo transfer, there have been a lack of randomized controlled studies. To provide further evidence, this study evaluated if a freeze-all strategy produces a greater number of live births than fresh embryo. Eligible individuals included women of any age who received their first or second cycle of IVF. Although there were no age exclusion criteria, the randomization was stratified based on age (<35 years or ≥35 years) along with study site.  Each study site had physicians determining possible interventions, number of embryos, and any specific regimens. The primary measure of success was the occurrence of a live birth (≥28 weeks of gestation) after the initial embryo transfer. The study randomized 838 eligible participants. Of the 419 women in the frozen embryo transfer group, 132 (32%) had a live birth, while 168 of 419 (40%) had a live birth in the fresh embryo transfer group (relative ratio 0.79 (95% CI 0.65 to 0.94); P=0.009). The frozen embryo transfer group also had a lower rate of pregnancy compared to the fresh embryo transfer group (39% (164 of 419) vs 47% (197 of 419); relative ratio 0.83 (0.71 to 0.97); P = 0.02). Pregnancy loss was greater in the frozen versus fresh embryo transfer group (31% (61 of 196) vs 23% (50 of 221); relative ratio 1.38 (1.00 to 1.90); P=0.05). Even after one year of randomization, the cumulative live birth rate was lower in the frozen embryo transfer group (44% (185 of 419)) compared to the fresh embryo transfer group (51% (215 of 419)) (relative ratio, 0.86 (0.75 to 0.99). In conclusion, fresh embryo transfer resulted in a higher number of live births, and cumulative live birth rate within one year of randomization, than frozen embryo transfer. In the future, women with low prognosis for IVF should consider fresh embryo transfer as it may be a better choice. 

Click to read the study in BMJ

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