Transferring One or Two Embryos in Surrogacy – What Is Recommended?

By: Dr. Yariv Gidoni, Specialist in Obstetrics, Gynecology, and Fertility

One of the central questions that arises at the beginning of the surrogacy process, especially for male couples (due to the desire for one child to be genetically related to each father), is whether to transfer one embryo or two. This decision involves not only the chances of success but also the health of the surrogate, as well as medical, emotional, and financial considerations – all leading to the ultimate goal: a healthy pregnancy and the birth of a healthy child.

Chances of Success – One Embryo vs. Two

• Single embryo transfer (at the blastocyst stage, high quality): Today this is considered the safest and most balanced option, primarily thanks to advanced IVF and cryopreservation techniques that allow the selection of embryos of very high quality.
• Double embryo transfer: May slightly increase the chances of pregnancy but does not guarantee significantly higher success, and it also carries a marked increase in the risk of multiple pregnancies.

Chances of Twin Pregnancy

When two embryos are transferred, the likelihood of a twin pregnancy is around 25%–30%. This is a significant factor, since twin pregnancies are considered high-risk for both the surrogate and the babies.

Medical Considerations

Twin pregnancies involve far greater health risks compared to singleton pregnancies:

• Risk of preterm birth: About 60% of twin pregnancies end before week 37, compared with about 10% in singleton pregnancies. Preterm birth can lead to prematurity and prolonged NICU hospitalization.
• Low birth weight: Higher likelihood of babies born under 2.5 kg, associated with respiratory problems, feeding difficulties, and developmental delays.
• Complications for the surrogate: Increased rates of gestational diabetes, preeclampsia, anemia, bleeding, back pain, and functional limitations.
• Higher risk of cesarean delivery: Cesarean rates are almost twice as high in twin pregnancies.
• Fetal loss or “vanishing twin”: In some cases, one embryo stops developing, which can complicate the entire pregnancy.

Emotional Considerations

• Intended parents often feel pressured to “succeed the first time” and may view transferring two embryos as a way to increase their chances. However, it is essential to understand that pregnancy is not only about the result – it is a long and complex journey for the surrogate.
• A twin pregnancy requires the surrogate to cope daily with greater physical strain, more restrictions, and sometimes the inability to continue working, which also affects her emotional and financial well-being.
• A surrogate who feels supported and secure during pregnancy is more likely to have a stable experience – something critical for the babies’ health as well.

Financial Considerations

• Costs of a twin pregnancy: Increased likelihood of additional medical expenses – more checkups, hospitalizations, treatments, and sometimes extended NICU stays.
• Potential advantage: For male couples, the option of transferring one embryo from each father could result in non-identical twins, thereby saving the need for a second surrogacy journey. However, this still involves the same elevated medical risks.
• Cost vs. risk: While in theory this approach might shorten the path to two children, in practice it brings significant medical and financial risks that may prove more burdensome over time.

Ethical and Legal Considerations

• Transferring two embryos raises questions of medical responsibility toward the surrogate, since she is the one carrying the increased health risk.
• In many countries – and in some clinics in Israel as well – there is a clear recommendation to prefer single embryo transfer (SET) when high-quality embryos are available.
• Some surrogacy contracts even limit the number of embryos that can be transferred.

So, What Is Recommended?

In most cases, transferring a single high-quality blastocyst – especially following preimplantation genetic testing (PGT/PGD) – is considered the safest, most balanced, and medically sound choice. This is also the consensus among most fertility specialists today. A single embryo transfer reduces significant risks, protects the surrogate’s health, minimizes the likelihood of complications from prematurity – and leads to the most desired outcome: the birth of a healthy child, in loving arms, within a safe environment.