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Is single embryo transfer right for me?

single embryo transferHow many embryos should we transfer? The answer to this question has changed over the years. Twenty years ago, IVF had a pregnancy rate of approximately 25% per cycle even in young patients. At that time, we routinely transferred 3 – 4 embryos and still the pregnancy rate was quite low.

There have since been significant improvements in in vitro fertilization (IVF). There have been improvements in stimulation protocols, availability of micromanipulation techniques [intracytoplasmic sperm injection (ICSI) and assisted zona hatching (AZH)], culture conditions in the embryology laboratory, blastocyst culture, embryo transfer technique, and other areas.

These changes have collectively resulted in a significant increase in pregnancy rates. Currently, the US national average IVF live birth rate in young patients is around 46% per transfer, and the number of embryos being transferred is around two.

But what is the correct number of embryos that should be transferred?

Fact: Our patients actually want twins!

It is common for a couple to want two embryos for transfer, as a lot of infertile couples actually want twins. Actually, they want healthy twins. Twin pregnancy is a common occurrence with the transfer of two embryos, where almost a third of the pregnancies will be twin. Some of the pregnancies (approximately 2%) will be triplet if one of the embryos splits into two.

Why is a multiple pregnancy considered high-risk?

Multiple pregnancies are considered high-risk for both mother and child. Maternal complications include gestational diabetes and high blood pressure, which could lead to pre-eclampsia, along with other medical conditions. Some women may even experience more nauseas and vomiting during the first 12 weeks of pregnancy as compared to woman pregnant with a singleton.

Another risk is miscarriage, which occurs in 1 out of 3 pregnancies with a multiple gestation. Additionally, it is very common for multiples to be born premature. If they are born prior to 36 weeks they may have issues with their lungs, gastrointestinal issues, chance of being born with cerebral palsy or other accompanying problems. With premature delivery this could then result with one or more of the babies needing to stay in the hospital for more intensive care due to the stage of development at the time of delivery. The overall cost of care (including hospital costs) of a multiple pregnancy is in excess of $100,000 each.

So, why do we transfer more than one embryo?

30 – 70% of human embryos are chromosomally abnormal. Most abnormal embryos will not implant. Some will implant and miscarry and others will result in birth of a baby with a chromosomal abnormality (e.g. Down syndrome). In older women, the incidence of chromosomally abnormal embryos is even higher. This is the reason why we transfer more than one embryo in our patients. The hope is that at least one of them will be normal and result in a baby. However, sometimes, both will be normal with a resultant multiple pregnancy.

Why not transfer a single embryo in all patients?

Elective single embryo transfer (eSET) is therefore a goal for all patients. This would reduce the incidence of multiple pregnancy. However, if we transferred only one embryo in all patients, it would result in a much lower pregnancy rate (especially in older patients).

Can we screen embryos for chromosomal abnormalities?

An ideal solution would be to test the embryos for chromosomal abnormalities PRIOR to transfer. This is called preimplantation genetic screening (PGS) and is dramatically changing the number of embryos we are transferring in our patients. After PGS, the fertility specialists at InVia Fertility are getting pregnancy rates with eSET that are comparable to what we were previously getting with transfer of multiple unscreened embryos.

We expect the number of twins to drop significantly with this strategy, which we are calling "smart IVF." In the immediate future, we expect the majority of our patients to screen their embryos prior to transfer. The correct number of embryos that should be transferred will then be: one.

To see a Board-certified fertility specialist who has the qualifications and experience to help you decide how many embryos to transfer,make an appointment at one of InVia's four Chicago area fertility clinics.

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IVF InVia Fertility Specialists Embryology

Deanna Fedorenko

Deanna Fedorenko

Deanna graduated as a medical assistant from First Institute and joined the team of InVia in April 2012. For 2 years prior to working here, she was a nursing assistant. Deanna enjoys working with patients and providing them with excellent care. At InVia, she continues to enjoy helping couples pursue their dream of having a healthy, happy, and growing family.


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