Single vs Double Embryo Transfer: Which Is Safer?
For many years, success in fertility treatment was measured by one simple outcome: achieving a pregnancy. In the early days of IVF, transferring multiple embryos was common practice because it increased the chances of implantation and pregnancy.
As a result, twin and triplet pregnancies became much more frequent among fertility patients than in the general population.
Today, fertility specialists have a different goal. Success is no longer defined simply by a positive pregnancy test. Instead, the aim is to help patients achieve the birth of a healthy baby while minimising risks for both mother and child.
Why Multiple Pregnancy Is No Longer Considered the Ideal Outcome
Many patients are surprised to learn that fertility specialists do not consider twins the “perfect result” of IVF treatment.
While the idea of completing a family with one pregnancy may seem attractive, carrying more than one baby significantly increases the likelihood of pregnancy complications.
Compared with singleton pregnancies, twin pregnancies are associated with:
- Higher rates of premature birth
- Increased risk of low birth weight
- Greater likelihood of neonatal intensive care admission
- Pregnancy-induced hypertension and pre-eclampsia
- Gestational diabetes
- Increased rates of caesarean delivery
- Higher maternal and neonatal morbidity
The risks become even greater in triplet or higher-order pregnancies.
How IVF in Spain Has Changed
Advances in reproductive medicine have dramatically improved embryo selection.
Modern IVF laboratories can now identify embryos with the highest implantation potential through:
- Extended embryo culture to the blastocyst stage
- Time-lapse embryo monitoring systems with AI
- Improved embryo grading techniques
- Preimplantation Genetic Testing (PGT) in selected cases
- Advanced laboratory culture conditions
Because of these improvements, transferring more embryos is often unnecessary.
What Is Single Embryo Transfer (SET)?
Single Embryo Transfer (SET) involves transferring just one embryo into the uterus during an IVF treatmeent o egg donation cycle.
This approach has become increasingly common worldwide because it allows fertility clinics to maintain excellent success rates while significantly reducing the chance of twins or higher-order pregnancies.
In many patients, especially younger women or those with high-quality blastocysts, transferring a single embryo provides outcomes comparable to transferring two embryos over multiple treatment attempts, but with far fewer complications.
Does Transferring One Embryo Reduce Success Rates?
This is one of the most common concerns among fertility patients.
The answer depends on individual circumstances, but in many cases and in modern clinics embryo selection techniques allow clinics to achieve the same pregnancy rates with a single embryo transfer.
When additional good-quality embryos are available, they can be vitrified and transferred in future cycles if needed, helping maintain strong cumulative pregnancy rates without increasing the risks associated with multiple gestations.
Individualised Treatment Is Essential
Not every patient has the same prognosis, and the number of embryos recommended for transfer should always be discussed with a fertility specialist.
Factors such as age, embryo quality, medical history and previous treatment outcomes all play a role in determining the most appropriate strategy.
The objective is always the same: achieving the safest possible pregnancy while maximising the chance of taking home a healthy baby.
Looking for Safe and Effective IVF Treatment in Spain?
At Fertility Clinic Spain, we believe that successful fertility treatment means more than achieving pregnancy. Our focus is helping patients build healthy families through evidence-based, personalised care.
If you would like to learn more about IVF treatment options, embryo transfer strategies or your chances of success, contact our team and arrange a free online consultation.