How Many Embryos Should You Transfer in IVF? (Age Specific Guidelines)

How many embryos should you transfer following IVF?

In this post, you will learn

  • The ASRM recommendations for how many embryos to transfer based on age
  • The pros and cons of single embryo transfer vs. multiple embryo transfer
  • When to transfer more than one embryo and for whom

Keep reading to learn more.

How many embryos should you trasnfer cover image

Disclaimer:

Although I am a physician by profession, I am not YOUR physician. All content and information on this website are for informational and educational purposes only.  It does not constitute medical advice and does not establish any kind of doctor-client relationship by your use of this website. Although I strive to provide accurate general information, the information presented here is not intended for the prevention or treatment of infertility and it is not a substitute for medical or professional advice. You should not rely solely on this information. Always consult your physician in the area for your particular needs and circumstances prior to making any decisions whatsoever. Those who do not seek counsel from the appropriate health care authority assume the liability for any damage, loss, or injury which may occur.


How Many Embryos Should You Transfer Following IVF?

Several factors influence the decision of how many embryos to transfer following in vitro fertilization (IVF). These factors include the patient’s age, the quality of the embryos, the patient’s fertility history, and if the embryos have undergone genetic testing. 

The goal of IVF is to have a single healthy baby and reduce the chances of twins or triplets.

To promote a singleton pregnancy, The American Society for Reproductive Medicine (ASRM) and Society for Assisted Reproductive Technology (SART) published guidelines in 2017 to guide physicians and patients in selecting an appropriate number of embryos to transfer.

ASRM Guidelines on How Many Embryos to Transfer

  • For women under 35 without a medical history, the ASRM recommends transferring one embryo, regardless of the embryo stage (Day 3 cleavage stage embryo or blastocyst stage embryo).
  • For women ages 35-37, the ASRM recommends that we strongly consider transferring only one embryo.
  • For women ages 38-40, the ASRM recommends transferring no more than two blastocyst embryos or no more than three cleavage stage embryos.
  • For women over 40, the ASRM recommends transferring no more than three blastocyst embryos or no more than four cleavage stage embryos.
  • If the embryo has undergone preimplantation genetic testing (PGT), the ASRM recommends transferring only one euploid embryo (an embryo that has a normal chromosome number) regardless of the patient’s age.
  • If you do not conceive after more than one embryo transfer using the above recommendations, the ASRM suggests we consider transferring one additional embryo in a subsequent cycle.
PrognosisAge <3535-3738-4041-42
Cleavage stage embryo euploid1111
Cleavage stage embryo favorable untested11≤3≤4
Cleavage stage embryo not favorable≤2≤3≤4≤5
Blastocyst embryo euploid1111
Blastocyst embryo favorable untested11≤2≤3
Blastocyst embryo not favorable≤2≤2≤3≤3
image of a day 3 embryo with at least 6 cells
image of a day 5 blastocyst - a circlular structure with two distinguishable cell lines

Who Decides How Many Embryos To Transfer?

The decision of how many embryos to transfer is made jointly by the patient in consultation with their physician. The fertility specialist will consider the patient’s age, fertility history, the number of embryos available for IVF transfer, and the quality of the embryos.

However, if an IVF clinic routinely transfers more embryos than what is recommended by the ASRM, this can raise red flags by the medical board and result in an investigation.

Does Putting 2 Embryos Increase The Chances of a Live Birth?

When it comes to embryo transfer, more is not necessarily better. 

Several studies have found that transferring two embryos at once does not substantially increase the chances of live birth compared to transferring two cumulative embryos, but one at a time. (Study 1)(Study 2)(Study 3).

Transferring one embryo at a time (and a second embryo later if the first transfer is unsuccessful) significantly reduces the chances of multiple pregnancies.

As such, most fertility specialists recommend elective single embryo transfer and freezing of any remaining embryos for future use.

The Pros and Cons of Transferring More Than One Embryo

The primary benefit of transferring more than one embryo is that it may increase the chance of live birth in a single cycle (i.e., you get pregnant faster).

However, transferring multiple embryos increases the chances of twins or triplets, which can be dangerous for both the mother and the babies. 

Multiple births are associated with a higher risk of pregnancy-related complications such as:

  • gestational diabetes,
  • preeclampsia,
  • preterm labor,
  • preterm delivery, 
  • postpartum hemorrhage,
  • low birth weight, 
  • fetal demise, 
  • neonatal intensive care unit (NICU) admission
  • And more.

On the other hand, single embryo transfer (SET) reduces the likelihood of multiple births without significantly decreasing the live birth rate. (Assuming that up to two embryo transfer cycles are performed.)

With that said, IVF is an emotionally and physically demanding process. Undergoing multiple embryo transfer treatment cycles requires additional time, money, and emotional energy.

You can learn more about frozen embryos and frozen embryo transfers here.

What Are The Chances Of Twins Following A Transfer of 2 Embryos?

The chances of twins following a transfer of two embryos vary based on patient age, embryo quality, and embryo stage.

Some reports have found that the chances of twins are as high as 30% with the transfer of two blastocyst-stage embryos.

Can 1 Embryo Become Twins?

A single fertilized egg can split into twins in a process called monozygotic twinning. Monozygotic twins (or “identical” twins) following a single embryo transfer are relatively rare and occur in about 1 to 2% of IVF pregnancies. 

In rarer instances, one embryo can split into three and form a monozygotic triplet pregnancy.

How Many Embryos Do You Need To Have A Baby?

A single euploid embryo has a 60-70% chance of implantation and a ~60% chance of live birth. However, it is essential to remember that these are general statistics and that every patient is unique.

For some patients, one euploid embryo is enough, and others will need two or more.

If your embryos are untested, you will likely need more embryos to increase your chances of live birth, particularly if you are over 35.

Why Does IVF Fail With “Perfect” Embryos?

There are three possible reasons why an IVF cycle may fail despite the transfer of good quality embryos:

1) Embryo quality: We cannot know if the embryo is “perfect.” Although we can test embryos for chromosomal abnormalities, there may still be other abnormalities we cannot yet test for.

2) Endometrium: Implantation is a complex process that involves many factors such as the uterine lining, the timing of the transfer, and the environment in the uterus, which may not be conducive to implantation. 

3) The Transfer Technique:  The embryo transfer is a delicate procedure that must be performed correctly to maximize pregnancy rates. Many fertility clinics use an abdominal ultrasound to ensure that we place the embryo in a good position in the uterine cavity. A difficult embryo transfer (due to cervical stenosis or other anatomical issues) may reduce the implantation rate.

Summary of Recommendations

Below are the ASRM recommendations based on the woman’s age.

Don’t forget; the ASRM recommends a single-embryo transfer in all women regardless of age if the embryo is euploid.

How Many Embryos To Transfer Below Age 35

  • The ASRM recommends transferring one embryo in women below age 35 with a favorable prognosis.*
  • If you have a history of prior failed embryo transfers, your doctor may suggest transferring up to two embryos, regardless of stage.

How Many Embryos To Transfer Between 35-37

  • The ASRM recommends transferring one embryo in women 35-37 with a favorable prognosis.*
  • If you have a history of prior failed embryo transfers, your doctor may suggest transferring up to two blastocysts embryos, or up to three cleavage stage embryos.

How Many Embryos To Transfer At Age 38 

  • The ASRM recommends transferring up to three cleavage stage embryos or up to two blastocysts in women aged 38 with a favorable prognosis.*
  • If you have a history of prior failed embryo transfers, your doctor may suggest transferring up to three blastocysts embryos or up to four cleavage stage embryos.

How Many Embryos To Transfer At Age 39

  • The ASRM recommends transferring up to three cleavage stage embryos or up to two blastocysts in women aged 39 with a favorable prognosis.*
  • If you have a history of prior failed embryo transfers, your doctor may suggest transferring up to three blastocysts embryos or up to four cleavage stage embryos.

How Many Embryos To Transfer At Age 40

  • The ASRM recommends transferring up to three cleavage stage embryos or up to two blastocysts in women aged 40 with a favorable prognosis.*
  • If you have a history of prior failed embryo transfers, your doctor may suggest transferring up to three blastocysts embryos or up to four cleavage stage embryos.

How Many Embryos To Transfer Over 40

  • The ASRM recommends transferring up to four cleavage stage embryos or up to three blastocysts in women aged 41 to 42 with a favorable prognosis.*
  • If you have a history of prior failed embryo transfers, your doctor may suggest transferring up to three blastocysts embryos or up to five cleavage stage embryos.

*Favorable Prognoses: 

  • Having one or more high-quality embryos
  • Having euploid embryos
  • Having a previous child from IVF 

What About FET Cycles?

When determining how many embryos to transfer in a frozen embryo transfer cycle, the woman’s age at the time of embryo freezing should be used, not the woman’s current age. 

What About Donor Egg Cycles?

When determining how many embryos to transfer in a donor egg cycle, the donor’s age should be used, not the recipient’s age.

Related Articles:


Make An Appointment With Dr. Robles To Discuss Your Fertility Options Today!


alex robles md

Alex Robles, MD

Dr. Alex Robles is a Spanish-speaking Latino-American Reproductive Endocrinologist and Infertility specialist in New York City, and a board-certified OBGYN. He has a special interest in health, lifestyle, & nutrition. Make an appointment with Dr. Robles to discuss your fertility options today!


References:

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  2. Forman, E.J., Hong, K.H., Ferry, K.M., Tao, X., Taylor, D., Levy, B., Treff, N.R. and Scott Jr, R.T., 2013. In vitro fertilization with single euploid blastocyst transfer: a randomized controlled trial. Fertility and sterility100(1), pp.100-107.
  3. Kamath MS, Mascarenhas M, Kirubakaran R, Bhattacharya S. Number of embryos for transfer following in vitro fertilisation or intra-cytoplasmic sperm injection. Cochrane Database Syst Rev. 2020 Aug 21;8(8):CD003416. DOI: 10.1002/14651858.CD003416.pub5. PMID: 32827168; PMCID: PMC8094586.
  4. Dallagiovanna C, Vanni VS, Somigliana E, Busnelli A, Papaleo E, Villanacci R, Candiani M, Reschini M. Risk Factors for Monozygotic Twins in IVF-ICSI Cycles: a Case-Control Study. Reprod Sci. 2021 May;28(5):1421-1427. doi: 10.1007/s43032-020-00406-0. Epub 2020 Nov 30. PMID: 33258063.
  5. Pirate P, De Ziegler D, Tao X, Sun L, Zhan Y, Ayoubi JM, Seli E, Franasiak JM, Scott RT Jr. Rate of true recurrent implantation failure is low: results of three successive frozen euploid single embryo transfers. Fertil Steril. 2021 Jan;115(1):45-53. DOI: 10.1016/j.fertnstert.2020.07.002. Epub 2020 Oct 16. PMID: 33077239.
  6. Phillips JA, Martins WP, Nastri CO, Raine-Fenning NJ. Difficult embryo transfers or blood on catheter and assisted reproductive outcomes: a systematic review and meta-analysis. Eur J Obstet Gynecol Reprod Biol. 2013 Jun;168(2):121-8. DOI: 10.1016/j.ejogrb.2012.12.030. Epub 2013 Jan 22. PMID: 23347607.

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