How Many Embryos Should You Transfer?

For most patients the answer is one. Transferring two embryos raises the chance that both implant, and a twin pregnancy is a higher-risk pregnancy for both mother and babies, with a substantially raised chance of preterm birth, low birth weight and neonatal intensive care. Elective single embryo transfer is now standard practice for patients who meet the criteria, because transferring the remaining embryos one at a time in later cycles gives a comparable cumulative chance of a baby without the risks of carrying two at once.

Why not just transfer two?

Because the goal is one healthy baby, and transferring two pursues a faster result at the cost of a riskier pregnancy.

Twin pregnancies carry materially higher risks than singleton pregnancies: preterm delivery, low birth weight, and a greater likelihood that the babies need intensive care. For the mother, the risks of gestational diabetes, high blood pressure and preeclampsia, and of caesarean delivery, are all raised. These are not remote possibilities; they are the expected profile of a twin pregnancy.

The point that changes most people's thinking is this: if you have several good embryos, transferring them one at a time across successive cycles gives a comparable cumulative chance of a baby. Transferring two at once does not create a new chance so much as bring forward and combine two.

What influences the decision?

Age

Under 35, single transfer is generally recommended, because implantation rates are higher and the twin risk is correspondingly greater. In the late thirties and forties, where the chance per embryo is lower, transferring two is sometimes considered, and that discussion should include what happens if both implant.

Embryo quality and stage

A good quality blastocyst, a day five or six embryo, generally has a better chance than a day three embryo, which strengthens the case for transferring one. Grading is one input among several rather than a guarantee.

Previous cycles

Repeated unsuccessful transfers of good embryos may change the discussion, though the reason for those failures matters more than the number.

Your own medical history

A uterine abnormality, previous preterm birth, or a medical condition that makes a twin pregnancy more dangerous can make single transfer the only safe option regardless of anything else.

What about frozen embryos?

Freezing is what makes single transfer practical. Embryos not transferred in this cycle can be frozen and transferred later, so choosing one now does not mean discarding the chance the others represent. Ask us about our freezing and thaw survival rates, since those figures bear directly on this decision.

What to ask before deciding

• What is the chance of pregnancy with one embryo in my case?
• What is the chance of twins if two are transferred?
• How many embryos do I have, and how many are suitable for freezing?
• What would a twin pregnancy mean given my medical history?
• What is the cumulative chance across successive single transfers, compared with one double transfer?

The last question is the one that reframes the decision, because it compares like with like.

We at Millennium IVF Clinic will go through what applies to your embryos and your history. You can arrange a consultation with our team.

Frequently asked questions

Does transferring two embryos double my chances?

No. It raises the chance that at least one implants, and it also raises the chance that both do. Across successive single transfers the cumulative chance is comparable without the twin risk.

Can I ask for two embryos to be transferred?

It is a discussion with your specialist, who will advise based on your age, embryo quality and medical history. In some cases it is not clinically appropriate.

Are IVF twins riskier than natural twins?

The risks of a twin pregnancy are broadly those of carrying two babies however it arose. The difference with IVF is that it is a choice, which is why it is worth deciding deliberately.

What if I only have one embryo?

Then the decision is made. Discuss with your specialist what happens if the transfer is unsuccessful and whether another collection cycle is advisable.