Have you thought about how many embryos to transfer in your IVF cycle, or just left the decision to the doctor?
Different countries have different policies regarding the number of embryos that should be transferred in an IVF cycle, and in countries where multiple embryo transfer is allowed, this decision is best made after a thorough discussion with your doctor.
It is important to remember that the primary goal of IVF treatment is to deliver one healthy baby at full-term and transferring multiple embryos may actually be harmful sometimes.
Should you transfer multiple embryos?
Transferring multiple embryos raises your chances of a successful pregnancy but it could be risky to transfer more than two. According to a European study analyzing 125,000 IVF cycles in the UK, implantation of three or more embryos in an IVF cycle is actually dangerous and does not improve your chances of having a baby.
The researchers found that transferring more than three embryos even in women over 40, is not medically justified, but it was being routinely done in around 30% of IVF cycles performed in the US.
With better understanding of IVF success and to reduce the number of multiple pregnancies in ART treatments, ASRM and SART have revised their guidelines to recommend transferring a single euploid blastocyst.
However, there is no law in the US to dictate the number of embryos you can transfer, as they want to allow treatment plans to be customized to each individual’s requirements and unique circumstances.
Considering individual clinical conditions including patient age, parity, gamete and embryo quality, medical situation, cryopreservation, etc., it may be justified to transfer less or more embryos in different situations and the US wants to leave it to the discretion of the doctor and they might be right in doing so.
Transferring 3 embryos lowers birth rate
The 124,148 IVF cycles analyzed by researchers at the University of Bristol, resulted in 33,514 babies being born.
In women under the age of 40, it was found that the live birth rate was higher on transferring two embryos as compared to one. However, the live birth rate was lower when they transferred three embryos in younger women, while in older women, it made no difference.
Risks of multiple embryo transfer
The study also corroborated a known fact—transferring multiple embryos raised the risk of adverse birth outcomes such as preterm delivery, low weight at birth, etc.
“A clear implication of our study is that [the] transfer of three embryos should no longer be supported in women of any age,” concluded study authors, Nelson and Lawlor.
Multiple embryo transfer may result in multiple pregnancies, which is risky for both you and your babies.
The risks associated with multiple pregnancies include:
For your babies:
- Premature birth
- Low birth weight
- Birth defects
- Chronic medical problems
For you, the mother:
- Anaemia
- Pre-eclampsia
- Gestational diabetes
- Need for a C-section
- Excess blood loss during delivery
What factors determine the number of embryos to be transferred?
There are certain factors that you will need to take into consideration when making this decision; these include:
- The quality of your gametes and embryos: If euploid blastocysts are available, the transfer of a single euploid blastocyst has the best prognosis.
- Your age: Transfer of a single euploid embryo is advisable, especially in women under 35. For patients between 38 and 40 years of age, no more than three cleavage-stage embryos or two blastocysts should be transferred. In cases where euploid embryos are available, a single-blastocyst embryo transfer should be the norm.
- Previous failures with fertility treatment: An additional embryo for transfer can be considered in women, who have previously failed IVF cycles.
- Any medical conditions: Uterine malformations, that may make successful implantation less likely also call for transfer of two embryos.
- Donor egg IVF cycles: If the age of the egg donor is under 35, the transfer of only one embryo is recommended.
Put back one or two embryos?
Weighing up the risks and benefits, most doctors will now decide to transfer back only a single, good quality embryo. Multiple pregnancy is the single, most-avoidable risk of IVF, which can pose major health risks to you and your babies.
When transferring only one embryo, your chances of a multiple pregnancy are only about 1-2%. However, they can be as high as 35% if you transfer back 2 embryos.
Our associate IVF doctors in Malaysia have extensive research in this matter and they demonstrated that a day-5 transfer of a single high-quality blastocyst provides clinical pregnancy rate of 82.9 percent and implantation rate of 79.5 percent.
This is corroborated by research published in the journal Human Reproduction, which shows that a transfer with a single, good quality embryo is just as effective as a double transfer in women under the age of 38 in their first IVF cycle.
However, the data looks specifically at younger women, with the majority included in the studies being under 40 years old. Maternal age can affect the success rates of IVF cycles and, will therefore be something you will want to take into consideration when deciding whether to transfer one or two embryos.
Your doctor may decide to transfer two embryos if you:
- are over 40 years
- have poor quality embryos
- have had previous failed fertility treatments
- have a medical condition which may affect successful implantation
Researchers have noted that risks of multiple births and other complications associated with transferring two embryos are lower in women over 40 than for younger women.
Our top fertility doctors in Malaysia also presented the below report after studying 396 IVF cases
Most clinics will offer you embryo monitoring or pre-implantation genetic screening, to ensure only the highest quality embryos are transferred. This negates the need for transferring multiple embryos.
Are three embryos ever transferred?
These days, most clinics will choose to transfer just one or two embryos, depending on your circumstances.
Research has shown that the risks of transferring three embryos outweigh the benefits. The transfer of three or more embryos should be avoided as it can significantly increase risks such as premature birth, and infact, it lowers the chances of a live birth.
Transferring more embryos on day-3 vs. day-5
Majority of fertility clinics will choose to transfer either one or two good quality embryos on day 5 (blastocyst stage).
However, you may be advised to transfer your embryos at day 3, particularly if you have a low number of relatively poor-quality embryos. This is because the uterine environment may provide a better chance of growth for the embryos as compared to the IVF laboratory.
Sometimes, if you do have embryos transferred on day 3, your doctors may advise you to transfer up to four embryos to improve your chances of a successful pregnancy.
However, if your clinic insists on transferring embryos on day-3 and not developing them to the blastocyst stage for any other reason, they may not be adequately equipped. You must consider this factor while selecting your IVF clinic.
Cost of embryo transfer
Given the high cost of IVF treatment, you will want to maximize your chances of a successful pregnancy as much as possible.
Transferring multiple embryos may save you the costs of further IVF treatment. Alternatively, you may freeze any remaining embryos; giving you the option to pay for a frozen embryo transfer, should the first one fail. This will work out significantly cheaper than a further full IVF cycle.
All good clinics today provide the option to freeze your embryos, which can be transferred later, eliminating the need for a full IVF cycle again.
Given all of the factors that need to be considered, the decision on how many embryos to transfer during your IVF cycle is a very important and difficult one. This should be carefully discussed between yourself, your partner, and your medical team, and the decision should be based on achieving the best result, keeping in mind your unique circumstances.
For more information on IVF and the number of embryos to be transferred, please get in touch using the form on this page or consult with any of our top fertility experts.
Resources:
Nelson SM, Lawlor DA (2011) Predicting Live Birth, Preterm Delivery, and Low Birth Weight in Infants Born from In Vitro Fertilisation: A Prospective Study of 144,018 Treatment Cycles. PLoS Med 8(1): e1000386. https://doi.org/10.1371/journal.pmed.1000386
Nelson SM, Lawlor DA (2012) Effect of age on decisions about the numbers of embryos to transfer in assisted conception: a prospective study https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(11)61267-1/fulltext
J. Gerris, P. De Sutter, D. De Neubourg, E. Van Royen, J. Vander Elst, K. Mangelschots, M. Vercruyssen, P. Kok, M. Elseviers, L. Annemans, P. Pauwels, M. Dhont, A real‐life prospective health economic study of elective single embryo transfer versus two‐embryo transfer in first IVF/ICSI cycles, Human Reproduction, Volume 19, Issue 4, April 2004, Pages 917–923, https://doi.org/10.1093/humrep/deh188