Deciding how many embryos are implanted in IVF depends on several factors, including the mother’s age, history of previous cycles, and embryo quality. Safety and long-term health outcomes for the mother and the baby (or babies) are equally crucial.
This article explains the difference between single and multiple embryo transfers, the factors that influence how many embryos your doctor may recommend, and how to decide which embryo(s) to transfer first.
How many embryos can be transferred during IVF?
When it’s time to decide how many embryos to transfer in IVF, most patients have two options:
Single embryo transfer (SET): Only one embryo is placed into the uterus during a transfer cycle.
Multiple embryo transfer (MET): Two or more embryos are transferred at once.
Clinics predominantly advise single embryo transfers. Double embryo transfers are done occasionally. The maximum advised by your clinic can vary with age, embryo stage, prognosis and even local law.
Source: Pavel Danilyuk
The decision on how many embryos are implanted during IVF can significantly impact the success of the IVF cycle and the health of the mother and the baby. In recent years, single embryo transfers have been a preferred choice by many fertility specialists and their patients due to advances in embryo screening, freezing techniques, and implantation success rates, especially if high-quality embryos are available.
Still, double or multiple embryo transfers may be considered in specific cases. Here is a quick look at the pros and cons of each option:
Transfer type | Pros | Cons |
|---|---|---|
Single embryo transfer |
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Multiple embryo transfer |
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4 factors that guide embryo transfer decisions
Clinic guidelines, patient preferences, and medical history all play a role in deciding how many embryos are transferred during IVF. The following factors are crucial for the decision:
Maternal age
Embryo quality
Previous IVF outcomes
Overall health and uterine environment
The goal is to achieve pregnancy while minimizing risks to you and your baby.
1. Maternal age
As you age, your egg quality and ovarian reserve decline. Fewer eggs are available, and the eggs retrieved are at a higher risk of having chromosomal abnormalities, which can affect the embryo’s ability to implant and develop into a healthy pregnancy.
Source: Nataliya Vaitkevich
This decline becomes more noticeable in the mid- to late-30s and accelerates after 40, which reduces the number of embryos created during IVF and the number of healthy embryos. Fertility doctors may recommend two or more embryos in older patients to improve the chances of at least one successful implantation.
Younger patients with good-quality embryos have higher implantation success per embryo, and therefore, a higher chance of twins or triplets if multiple embryos are transferred, so single embryo transfer is strongly recommended in these cases.
The table below shows an overview of IVF success rates by age group using a woman’s own eggs:
Age group | Overall live birth rate | Initial transfer live birth rate | Subsequent transfer live birth rate |
|---|---|---|---|
Under 35 | 55.6% | 41.4% | 47% |
36–37 | 40.8% | 31.6% | 44.7% |
38–40 | 26.8% | 22.3% | 40.9% |
Live birth rates for women over the age of 40 are about 7%, with women under 42 having higher success rates than those over 42. That is why many mothers of advanced age decide to use donor eggs.
2. Embryo quality
Clinics assess each embryo’s likelihood of implanting based on two key methods:
Morphological grading: It’s a visual evaluation of how well the embryo is developing, examining factors such as cell number and symmetry, inner cell mass and trophectoderm appearance, and rate of development relative to expected timelines.
Preimplantation genetic testing: Some patients choose to screen their embryos for chromosomal normality through PGT-A. This can help identify which embryos are euploid (chromosomally normal). They are far more likely to implant successfully and lead to a healthy live birth. Parents with known genetic conditions may also opt for PGT-M and identify embryos free from targeted single-gene disorders, such as hemophilia, muscular dystrophy, or cystic fibrosis.
When high-quality embryos are available, a single embryo transfer is recommended. If embryo quality is poor or uncertain, your clinician may recommend transferring more than one in a single cycle. This approach is primarily recommended if you have a history of failed IVF attempts.
Pro tip ♥️
Traditional embryo grading and standard preimplantation genetic testing, such as PGT-A, PGT-M, and PGT-SR, help identify whether an embryo appears healthy and has the correct number of chromosomes, but they don't reveal the whole picture. That is where preimplantation genetic testing for polygenic conditions (PGT-P) comes in.
PGT-P is an advanced form of genetic testing that analyzes an embryo’s polygenic risks — its genetic predisposition to complex diseases and traits influenced by many genes. This can include conditions such as:
Type 1 and 2 diabetes
Certain cancers (like breast or prostate cancer)
Cardiovascular disease
Autoimmune disease
PGT-P gives insight into long-term health risks. It can help you prioritize embryos with lower genetic risk profiles, adding more clarity to the embryo selection process.
Bonus read: Read more about preimplantation embryo testing in these guides:
3. Previous IVF outcomes
Patients who have had one or more failed transfers, especially when the embryo quality was good, may consider multiple embryo transfers to increase their chances. However, it is crucial to understand why previous cycles didn’t work.
If failures come from lower-quality embryos, selecting and transferring higher-quality ones may be more effective than increasing their number. Additionally, if uterine receptivity was the issue, transferring more embryos wouldn’t necessarily improve IVF success.
4. Overall health and uterine environment
Your overall health, especially the condition of your uterus, plays a significant role in embryo transfer planning. Structural issues, such as fibroids, endometrial polyps, and intrauterine adhesions or scarring, can interfere with embryo implantation or increase the risk of miscarriage, regardless of how many embryos are transferred.
Your general health and pregnancy history help determine whether it’s safe to carry a multiple pregnancy. Some health conditions make it safer to transfer only one embryo at a time to reduce the strain on the body and avoid complications during pregnancy.
Your doctor may recommend a single embryo transfer if you have:
Cardiovascular disease: Pregnancy, especially with multiples, increases the heart’s workload.
Kidney disease: Kidney issues can worsen during pregnancy, and carrying twins increases the risk of preeclampsia and other complications.
Diabetes or prediabetes: Managing blood sugar during pregnancy is more challenging with multiples.
Thyroid disorders: Poor thyroid function can interfere with both implantation and the course of pregnancy.
How many embryos per IVF cycle should you transfer?
IVF is emotionally, physically, and financially demanding, so it’s natural to want to conceive as quickly as possible, ideally in a single cycle. MET does, in some cases, offer a slightly higher chance of getting pregnant, especially in patients with a lower likelihood of implantation. However, SET is the safest and most effective choice for many patients.
Here is an overview of who the best candidates for both approaches are:
SET candidates | MET candidates |
|---|---|
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Risks of multiple embryo transfers
The main risk of multiple embryo transfers is a higher chance of multiple pregnancies.
While the idea of boosting your odds by transferring more than one embryo can seem appealing, carrying twins or higher-order multiples comes with risks both for you and the babies.
Source: Greta Fotografía
Carrying twins or triplets places greater physical strain on the body and increases the likelihood of:
Gestational diabetes, which affects how your body processes sugar during pregnancy
Preeclampsia or pregnancy-related high blood pressure that can potentially jeopardize both you and the baby
Anemia, more than twice as common in multiple pregnancies
Miscarriage, with pregnancy loss risks remaining higher in later trimesters
Placental abruption, when the placenta detaches from the uterus too early
Excessive bleeding during or after birth
Preterm labor and delivery, often leading to emergency C-section
Extended hospital stays and recovery times
Risks for babies include requiring neonatal intensive care (NICU) after birth.
Multiples are at risk of fetal growth restriction (also called intrauterine growth restriction or small for gestational age). This happens if one or more babies aren’t growing at the proper rate, and it might cause the babies to be born prematurely (before week 37), which can affect lung development, brain function, and feeding ability.
The condition often leads to a low birth weight (lower than 5.5 lbs), which increases the risk of infection, breathing problems, and developmental delays.
Multiple-birth babies are also at a higher risk of certain congenital problems, such as:
Digestive tract problems
Heart disease
Cerebral palsy
Spina bifida
Vision or hearing loss
Learning disabilities
How genetic testing helps reduce IVF risks and improve embryo selection
Genetic testing has become an essential part of the embryo selection process, not only for choosing chromosomally healthy embryos but also for gaining deeper insights into long-term health outcomes.
Modern PGT options make it easier and safer to opt for single embryo transfer without compromising your chances of success. While they don’t guarantee future outcomes, they give you a clearer view of each embryo’s health profile, helping you select the one most likely to thrive.
Preimplanation genetic testing can:
Support more confident single embryo transfers
Minimize the risk of complications from multiple pregnancies
Ensure peace of mind when choosing between embryos that all appear normal
Give your future baby the best possible start
If the choices seem overwhelming, it’s because they are. In vitro fertilization is a complex process, with many decisions to be made, so relying on professional support is advisable.
Parents who are ready to start IVF can schedule a consultation with Nucleus. Our team of experts will connect you with the best partner clinics, and we’ll work with you every step of the way to ensure you can access the right tests and choose embryos that have a better chance at survival. You’ll get best-in-class support, treatments, genetic testing, and care.
Nucleus IVF+ brings everything together, from Nucleus Family, a whole-genome carrier screening for more than 2,000 inherited conditions, to Nucleus Embryo, the first genetic optimization software that helps you analyze, compare, and select embryos based on health conditions, physical traits, and even well-being indicators.
How Nucleus IVF+ supports your IVF journey
IVF is no longer only about overcoming infertility. It’s a path many families choose to give their children the strongest possible start in life.
Nucleus IVF+ is designed to make your journey clearer, simpler, and more supportive. It combines advanced genetic optimization with family-first care and gives you the tools and guidance to make all the decisions with confidence. From the first consultation to the moment you select your embryo, you’ll know you’re backed by expert support and science that looks beyond basic viability.
With Nucleus, you can:
Understand your own genetic health through comprehensive carrier screening for over 2,000 inherited conditions
Get all-inclusive support for one IVF cycle, including clinic matching, ICSI, and medications
Compare embryos with clarity, using intuitive insights into health, traits, and long-term potential
Rely on expert guidance every step of the way, so you can focus on your family instead of trying to navigate the process alone
Nucleus IVF+ brings genetic optimization to everyone, letting parents be parents instead of juggling research, logistics, and complex medical decisions.
Book a call today and let Nucleus experts guide the way to a safe pregnancy and a healthy baby.
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Featured image source: MART Production
