In a nutshell
This study investigated if fresh (FR) or frozen (FZ) single embryo transfer (sET) is more successful in ovulating women. They found that singleton live birth rates were higher after FZ-sET.
After in vitro fertilization (IVF), embryos are transferred to the uterus. In some cases, only one embryo is transferred. This is called single embryo transfer (sET). In some practices, multiple embryos are transferred to improve the chances of implantation and live birth (LB). This can also lead to multiple pregnancies (MP). sET is becoming more popular to minimize MP.
sET is becoming more popular in recent years. However, there is still concern it may reduce the success of fertility treatment. The success of IVF and ET is determined by the live birth rate (LBR). If multiple embryos are transferred there is a greater chance of implantation. In order to maximize the success of sET, it is important to establish the best sET protocol. One aspect of this is using fresh (FR) or frozen (FZ) embryos. It is unclear if FR-sET or FZ-sET is associated with better LBR.
Methods & findings
This study included 1650 women undergoing IVF. Patients were randomly assigned to undergo FR-sET or FZ-sET. All patients underwent the standard IVF procedure. All embryos were cultured in a lab setting for 5 days after fertilization. At day 5 embryos were transferred in the FR-sET group. In the FZ-sET group, embryos were frozen and transferred at a later stage (up to 4 weeks). Some woment underwent ovarian stimulation (OS) to prepare the uterus. The outcome of interest was the LBR.
The LBR was 50.4% in the FZ-sET group and 39.9% in the FR-sET group. The odds of live birth were significantly higher (+26%) in the FZ-sET group. Frozen transfer was associated with higher implantation rates, clinical pregnancy, and ongoing pregnancy. FZ-sET was linked to reduced risk of ectopic pregnancy (pregnancy developing in another part than the womb) and underdeveloped fetus. FZ-sET was also linked to a higher risk of pre-eclampsia (high blood pressure in pregnancy), diabetes and overdeveloped fetus.
The bottom line
The authors concluded that singleton live birth rates were higher after FZ-sET.
The fine print
The women in this study were young and had no issues with ovulation. It is unclear If sET is practical for all women with fertility issues.
If you have any concerns regarding fertility treatment, please consult with your physician.
Published By :
Lancet (London, England)
Feb 28, 2019