Fresh vs. frozen: which type of embryo transfer is most successful for women undergoing IVF?

This study investigated if fresh (FR) or frozen (FZ) embryo transfer (ET) results in higher live birth rates (LBR) in women with undergoing in vitro fertilization (IVF).

They found that LBR was higher after FZET in women with high progesterone levels. 

Many women with fertility problems will undergo assisted reproduction (AR). AR technologies, or ARTs, included in vitro fertilization (IVF). After IVF, embryos are transferred to the uterus. This is known as embryo transfer (ET). ET can be performed with ‘fresh’ embryos (FRET). It can also be performed with frozen embryos (FZET). The success of FRET may be reduced if progesterone (PGN) levels are high. PGN is an important hormone in pregnancy. FRET may not be suitable when the endometrium (EDM, uterus lining) is thin.

FZET has become more popular in recent years. FZET does not need to be performed immediately after IVF. This means it can be implanted when the uterus is most receptive to an embryo. It is unclear if FZET or FRET is more successful in women undergoing IVF.

This study included 782 couples undergoing fertility treatment. They were randomly assigned to undergo either FRET or FZET after IVF (391 patients in each group). PGN levels were measured and categorized. There were 4 groups based on PGN level. EDM thickness was also measured. The main outcome was the live birth rate (LBR).

FZET was associated with higher LBR in women with PGN greater than 1.14ng/ml. Overall, LBR was significantly lower after FRET.

The authors concluded that LBRs were higher after FZET in women with high PGN levels.

Women with a thin EDM (less than 8 mm) were not included in the analysis. The number of patients In the study may have been too low to find some statistically significant differences. 

If you have any concerns regarding fertility treatment, please consult with your physician.