Link Between Age and Fertility

What Is Embryo Transfer?

Embryo transfer is the final step of an IVF cycle. After eggs are retrieved and fertilized in the lab, the resulting embryos are grown for several days — either to the cleavage stage (day 2–3) or, more commonly today, to the blastocyst stage (day 5–6). Your embryologist and fertility specialist then select the embryo or embryos considered most likely to implant successfully, and one or more are placed into the uterus using a thin, flexible catheter. It's a quick, generally painless outpatient procedure, but the decision of how many embryos to transfer is made well before you reach this stage.

There are two main approaches: single embryo transfer (SET), where one embryo is transferred per cycle, and multiple embryo transfer (MET), where two or more embryos are transferred at once. When SET is done using the healthiest available embryo by deliberate choice rather than necessity, it's often called elective single embryo transfer, or eSET.

Single vs Multiple Embryo Transfer: Factors Influencing the Decision

There isn't a one-size-fits-all rule. Fertility specialists weigh several factors before recommending single or multiple embryo transfer, and the conversation should always be individualized.

Age

Younger patients generally have higher-quality embryos and a better chance of implantation from a single transfer. Professional guidance from the American Society for Reproductive Medicine (ASRM) supports transferring just one embryo for patients under 35 with a favorable prognosis, since the pregnancy rate from a single good-quality blastocyst is comparable to transferring two, without the added risk of twins. For patients in their late 30s or early 40s, or those with a less favorable prognosis, transferring more than one embryo may be considered, though still within conservative limits.

Embryo Quality and Genetic Testing

A high-grade blastocyst has a strong likelihood of implanting on its own. When preimplantation genetic testing for aneuploidy (PGT-A) confirms an embryo is chromosomally normal, single embryo transfer is almost always the preferred path, since transferring one euploid embryo yields pregnancy rates similar to transferring two untested embryos, minus the risk of a twin pregnancy. Lower-grade or untested embryos may lead some specialists to discuss transferring more than one, particularly when embryo numbers are limited.

Number of Previous IVF Attempts

Patients who have had one or more unsuccessful embryo transfers, or who have a limited number of embryos remaining, may discuss multiple embryo transfer with their specialist. Even then, most clinics try to stay within evidence-based limits rather than transferring several embryos at once, since the primary goal remains a healthy singleton pregnancy.

Uterine and Overall Health

Conditions such as a history of uterine surgery, fibroids affecting the uterine cavity, or other structural or medical concerns can influence whether carrying twins would be safe. A patient with health conditions that make a multiple pregnancy riskier is usually steered firmly toward single embryo transfer.

Patient Preference and Family-Building Goals

Some patients feel drawn to the idea of having twins in one pregnancy, especially after a long or costly fertility journey. This is an understandable perspective, but it needs to be balanced against real medical risk. A thorough, honest conversation with your fertility specialist about what a twin pregnancy actually involves — for both parent and babies — is an essential part of informed decision-making.

Who Is a Good Candidate for Single Embryo Transfer?

Single embryo transfer is generally recommended for:

• Patients under 35 with good-quality blastocysts
• Patients whose embryos have undergone PGT-A and tested chromosomally normal
• Patients with a favorable overall prognosis, including adequate ovarian reserve and no major uterine concerns
• Patients who have a uterine or medical condition that makes a twin pregnancy higher risk
• Patients who have surplus embryos available for future frozen embryo transfer if the first attempt is unsuccessful

Multiple embryo transfer may be discussed, cautiously and within recommended limits, for patients with a less favorable prognosis — such as advanced maternal age, repeated implantation failure, or lower-grade embryos without genetic testing — always after a clear discussion of the added risks.

Benefits of Single Embryo Transfer

• Substantially lower chance of twin or higher-order multiple pregnancy
• Reduced risk of preterm birth, low birth weight, and related complications
• Lower risk of pregnancy complications for the parent, including gestational diabetes and preeclampsia
• Comparable live birth rates to multiple transfer in favorable-prognosis patients when using a high-quality or genetically tested embryo
• Remaining embryos can be frozen and used in a future cycle, giving more than one chance at pregnancy without repeating egg retrieval

Risks of Multiple Embryo Transfer

Transferring more than one embryo increases the chance of pregnancy occurring in a single cycle, but it also meaningfully raises the risk of a multiple pregnancy — and multiple pregnancies carry real, well-documented risks that shouldn't be minimized.

• Preterm birth: Twin pregnancies are far more likely to deliver early than singleton pregnancies, which raises the risk of complications for the babies, including underdeveloped lungs and low birth weight.
• Low birth weight: Babies from multiple pregnancies are, on average, smaller and more likely to need neonatal intensive care.
• Maternal complications: Carrying twins or more increases the likelihood of gestational diabetes, preeclampsia, hemorrhage, and the need for a cesarean delivery.
• Higher-order multiples: In rare cases, transferring more than one embryo can result in identical twinning within an already-multiple pregnancy, leading to triplets or more, which carries even greater risk.
• Long-term health considerations: Children from multiple pregnancies face a somewhat higher likelihood of developmental and health challenges linked to prematurity.

Because of these risks, national reproductive medicine bodies, including ASRM and the European Society of Human Reproduction and Embryology (ESHRE), have published guidance encouraging single embryo transfer as the default approach whenever the prognosis allows it.

The Embryo Transfer Procedure

Regardless of whether one or more embryos are being transferred, the procedure itself is similar. It's typically done without sedation, takes about 10–15 minutes, and is guided by ultrasound to help place the embryo(s) accurately within the uterine lining. You'll usually be asked to come in with a comfortably full bladder, as this helps with ultrasound visibility. Afterward, most clinics recommend a short rest period before you go home, followed by normal light activity — bed rest for days afterward isn't usually necessary or medically supported.

Whether the embryo is fresh (from the same cycle as the egg retrieval) or previously frozen (a frozen embryo transfer, or FET) also factors into planning, since frozen transfers allow more flexibility in timing the procedure to your body's readiness.

Recovery and What to Expect Afterward

After the transfer, most patients return to normal activities within a day or two, avoiding strenuous exercise and heavy lifting as a precaution rather than a strict medical requirement. Your clinic will likely prescribe progesterone support to help maintain the uterine lining. A pregnancy test is usually scheduled about 10–14 days after transfer. Mild cramping or light spotting can be normal, but you should always report significant pain, heavy bleeding, or fever to your care team.

Success Factors

Success in embryo transfer depends on far more than the number of embryos placed. The most influential factors include embryo quality and genetic normalcy, the receptivity of the uterine lining, the patient's age and ovarian reserve, the skill and experience of the transfer procedure itself, and overall health factors such as thyroid function and body weight. Transferring two embryos instead of one does not double your chances of pregnancy — for many patients with a good-quality embryo, it mainly increases the chance of twins rather than meaningfully improving the live birth rate. This is why modern IVF practice increasingly favors quality over quantity.

When Should You Consult a Specialist?

You should discuss the number of embryos to transfer with a fertility specialist as part of your treatment planning, ideally before you reach the transfer stage. This conversation is especially important if you are over 35, have had previous unsuccessful transfers, have a uterine or medical condition, or are unsure whether PGT-A testing is right for you. A specialist can review your embryo grading, medical history, and personal goals to recommend an approach that balances your chances of pregnancy with your safety and that of your future child.

Why Choose ART Fertility Clinics?

Choosing where to pursue IVF matters as much as the treatment decisions within it. ART Fertility Clinics brings together experienced reproductive specialists, embryologists, and support staff who follow evidence-based, internationally recognized protocols for embryo transfer, including individualized guidance on single versus multiple embryo transfer. Every patient's treatment plan is built around their specific medical history, embryo quality, and family-building goals, with transparent, honest counseling at every step. The team is committed to helping patients achieve a healthy pregnancy and a healthy baby — not simply the fastest possible result — with compassionate, patient-centered care throughout the IVF journey.

Conclusion

Conclusion Age affects fertility in both women and men, though the pace and pattern of change differ between the sexes. Female fertility declines gradually through the 20s and more sharply after the mid-30s, driven by falling egg quantity and quality, while male fertility changes more slowly but still meaningfully over time. Recognizing these patterns and understanding the diagnostic tools and treatment options available, from AMH testing to IVF and fertility preservation, can help individuals and couples make informed decisions about family planning. If you're concerned about how age may be affecting your fertility, speaking with a qualified fertility specialist is the most reliable way to understand your options and next steps.