Frozen vs. fresh – which embryo transfer method is better with a gonadotrophin-releasing hormone blocker?

This study compared fresh (Fr-ET) and frozen embryo transfer (Fz-ET) after controlled ovarian hyperstimulation (COH) with a gonadotrophin-releasing hormone antagonist (GnRH-at). They found that Fz-ET had better fertility outcomes with GnRH-at treatment. 

Controlled ovarian hyperstimulation (COH) is the first step in assisted reproduction (AR). Drugs cause the ovaries to release oocytes (eggs). Then AR procedures e.g. in vitro fertilization (IVF) can be performed. COH commonly involves a gonadotrophin-releasing hormone antagonist (GnRH-at). COH with GnRH-at is very effective. It is also safer than some drug regimens. Embryo transfer (ET) is performed after IVF. If this is done immediately it is called fresh ET (fr-ET). Embryos can also be frozen and transferred at another time. This is called frozen ET (fz-ET). 

After ET the fertilized embryo attaches to the endometrium (EDM). The EDM lines the uterus and supports the growing embryo. GnRH-at can lead to changes in the EDM. Some studies suggest that fr-ET is less successful than fz-ET. It is thought that the EDM is not as effective after GnRH-at COH. It is unclear if fertility outcomes after GnRH-at COH differ between fr-ET and fz-ET. 

This study included 1430 women undergoing COH with GnRH-at. Patients were grouped according to ET procedure into Fr-ET and Fz-ET. Fertility outcomes included clinical pregnancy rate (CPR) and miscarriage rate (MCR). Ectopic pregnancy rate (EPR) and the number of retrieved oocytes (NROs) were also analyzed. 

34.6% of women had Fr-ET and 63.4% had Fz-ET. Fz–ET was associated with a significantly higher CPR. The CPR was 63.7% in Fz-ET and 54.5% with Fr-ET. Fr-ET was associated with a higher NRO. The average NRO with Fr-ET and Fz-ET were 7.23 and 6.51.  There were no differences in MCR or EPR. 

The authors concluded that Fz-ET had better fertility outcomes with GnRH-at.

This was a retrospective study. This means the study was not controlled. Other factors may have influenced the findings. 

If you have any concerns regarding infertility treatments please consult with your physician.