Fresh embryo transfer boosts IVF success for low-prognosis women

Fresh embryo transfer boosts IVF success for low-prognosis women | Image Credit: © Medical Works - © Medical Works - stock.adobe.com.

The use of fresh embryo transfer during in vitro fertilization (IVF) may improve the odds of success in women with a low chance of having a healthy baby when compared to the use of frozen embryos, according to a recent study published in The BMJ.¹

In routine IVF treatment, all suitable embryos are frozen before treatment. This prevents the need to receive fresh eggs and risk overstimulation of the ovaries with fertility drugs. Data from women with a good prognosis of IVF success has indicated similar live birth rates between fresh and frozen embryo transfer.

According to investigators, “it’s unclear whether women with low prognosis also benefit from this strategy.” Therefore, a study was conducted to address this research gap.

Women receiving their first or second IVF cycle with low prognosis were included in the analysis.² Low prognosis was determined by having 9 or less oocytes, an antral follicle count below 5, or a serum anti-Müllerian hormone level below 8.

Exclusion criteria included being unsuitable for fresh embryo transfer and undergoing natural cycles for oocyte retrieval. Participants were randomized 1:1 to receive either frozen embryo transfer or fresh embryo transfer, with randomization stratified by being aged under 35 years or at least 35 years.

Ovarian stimulation could be performed with a gonadotrophin releasing hormone antagonist or a gonadotrophin releasing hormone agonist protocol. Doctors obtained oocyte samples at 34 to 36 hours following administration of human chorionic gonadotrophin.

Embryos with 7 to 10 cells and a morphological score of 3 or 4 were considered good quality. For blastocysts, good quality was determined by expansion stage 4 or more and a score of inner cell mass B or greater.

In the fresh embryo transfer group, embryo transfer was performed 3 to 5 days following oocyte retrieval. In the frozen embryo transfer group, embryo transfer was performed on the day of thawing. Women achieving pregnancy received luteal phase support for 10 to 11 weeks of gestation.

Live birth after the first embryo transfer was reported as the primary outcome. Clinical pregnancy, singleton or twin live pregnancy, ectopic pregnancy, pregnancy loss, singleton or twin live birth, maternal complications, neonatal complications, birth weight, heavy singleton live birth, and cumulative live birth were reported as secondary outcomes.

There were 838 women included in the final analysis, with 419 assigned to each group. Not undergoing embryo transfer within 1 year after randomization was reported in 5.3% of the frozen embryo transfer group and 0.5% of the fresh embryo transfer group. Similar baseline characteristics and ovarian stimulation outcomes were reported between groups.

A live birth was reported in 32% of the frozen embryo transfer group vs 40% of the fresh embryo transfer group. This indicated a difference of -8.6% and a relative ratio of 0.79.

For secondary outcomes, twin live birth rates were 5% vs 9%, respectively, clinical pregnancy 39% vs 47%, respectively, pregnancy loss 31% vs 23%, respectively, and cumulative live birth 44% vs 51%, respectively. No other secondary outcomes differed between groups.

“Fresh embryo transfer may be a better choice for women with low prognosis for IVF in terms of live birth rate compared with frozen embryo transfer,” said investigators. Authors also recommended additional research about strategies of accumulating embryos with back-to-back cycles.

References

1. Fresh embryo transfer may be better for women with low chance of IVF success. January 29, 2025. Accessed February 3, 2025. https://www.eurekalert.org/news-releases/1071884
2. Wei D, Sun Y, Zhao H, et al. Frozen versus fresh embryo transfer in women with low prognosis for in vitro fertilisation treatment: pragmatic, multicentre, randomised controlled trial. BMJ. 2025;388:e081474. doi:10.1136/bmj-2024-081474