Comparing the effectiveness of using frozen versus fresh embryos in IVF

The study compared the effectiveness of transferring frozen embryos (FzE) versus fresh embryos (FrE) for couples with infertility using in vitro fertilization (IVF). The main finding of the study was that using FzE over FrE in IVF did not improve the chance of having a healthy baby.

IVF is one of the procedures that help infertile couples conceive. IVF involves stimulating a woman's ovaries to produce eggs that are then collected and fertilized with the sperm in the lab. These fertilized eggs are called embryos. These embryos are then transferred into the woman’s uterus (womb) after fertilization. The embryos can be transferred fresh (FrE) or frozen (FzE). 

Many studies have shown that freezing embryos may result in high live birth rates. FzE transfer also has a lower risk of developing complications such as ovarian hyperstimulation syndrome (OHSS), low birth weight babies, and preterm babies compared to FrE. Studies have shown that FrE transfer may result in poorer outcomes for both, mother and baby. However, whether freezing all embryos and transferring a FzE would result in a higher chance of having a healthy baby compared to transferring a FrE is still under investigation.

This study included 616 couples with infertility undergoing IVF. 307 couples had a FzE transfer and 309 couples had a FrE transfer. After the first embryo transfer, women were followed up for pregnancy results.

The rate of delivering a healthy baby was 20.3% in the FzE group compared to 24.4% in the FrE group. This difference was not statistically significant. 

3.6% of women in the FzE group had OHSS compared to 8.1% of those in the FrE group. OHSS is a complication after hormonal treatment to stimulate the ovaries to produce eggs that results in painful swelling of the ovaries. The cases of OHSS were mild to moderate for the FzE group while the FrE group had 6 severe cases.

The live birth rate was 28.3% in the FzE group compared to 34.3% in the FrE group. The clinical pregnancy rate (pregnancy is confirmed by both blood tests and ultrasound imaging) was 33.9% for the FzE group compared to 40.1% in the FrE group. These differences were not considered statistically significant. The risk of miscarriage was also similar between the FzE group (14.3%) and the FrE group (12.9%).

The study concluded that frozen embryo transfer did not prove to have an increased chance of having a healthy baby after the first embryo transfer and it is more expensive compared to fresh embryo transfer in couples undergoing IVF.

The study sample size was small. Also, the study included only couples in the UK, which may not be representative of the general population.