Before starting IVF, a detailed discussion takes place between the couple, fertility specialist, and embryologist to decide how many embryos to transfer. The decision considers:
- The woman’s age
- Medical and fertility history
- Embryo quality (morphology and development stage)
- The couple’s preference
- The clinic’s standard practices
A key factor in this decision is the risk of multiple pregnancies. If a couple does not want to risk twins or higher-order multiples, only one embryo should be transferred.
Does Transferring Two Embryos Increase Pregnancy Chances?
Not necessarily. Each embryo has its own implantation potential, meaning:
- If an embryo is destined to implant, it will do so whether transferred alone or with another embryo.
- If two embryos are transferred together and both implant, a twin pregnancy occurs.
- If the same two embryos were transferred one at a time (one fresh, one frozen later), both could still lead to separate pregnancies.
Thus, transferring multiple embryos only speeds up the outcome (whether an embryo implants or not), but it increases the risk of twins.
Current Best Practices for Embryo Transfer
- For women under 35: Most clinics now recommend single embryo transfer (SET) to maximize success while minimizing twin risk.
- For older women: Since a higher proportion of embryos have chromosomal abnormalities, transferring two embryos may improve the chances of pregnancy while keeping the risk of twins relatively low.
This trend toward SET is even stronger when embryos are cultured to Day 5 (blastocyst stage), as these embryos have higher implantation potential, making multiple transfers less necessary.
