Why Doctors Insist on Single Embryo Transfers
I.Multiple Pregnancy Crisis: Why does the medical community “talk about double”?
The global advancement of assisted reproductive technology (ART) has led to a significant increase in clinical pregnancy rates, but the ensuing multiple pregnancies have become the most serious complication. Data show that the preterm birth rate of twin pregnancies is as high as 60%, and the rate of triple pregnancies is even closer to 100% – not only threatening the safety of mothers and babies, but also posing a heavy medical burden.
- Maternal risk: each pregnancy is a test of life
Hypertension during pregnancy: the incidence rate of twin pregnancies reaches 40%, which is four times higher than that of single pregnancies.
Post-partum hemorrhage: uterine over-distension leads to weak contractions and a 3-fold increase in the risk of bleeding >1000ml.
Long-term health effects: multiple pregnancies raise the probability of gestational diabetes remaining as type 2 diabetes by 30%.
- Fetal pitfalls: preterm birth and developmental challenges
Very low birth weight (VLBW): 50% of twins with birth weight <2500g have a 25% increased risk of neurodevelopmental delay.
Congenital malformations: Twin fetuses have twice the rate of single fetus malformations, with a 4.6% incidence of heart defects.
Case warning: 32-year-old Emma was pregnant with twin babies from a double embryo transfer. Cervical insufficiency occurred at 26 weeks’ gestation, and ultimately neither of the babies survived.
II.The Scientific Advantages of Single Embryo Transfer (SET): Data-Driven Selection
- Blastocyst culture: the best of the best in natural selection
Developmental potential assessment: only 40% of fertilized eggs can develop to blastocyst stage (day 5-6), eliminating chromosomally abnormal embryos naturally.
Morphologic grading: 65% of Grade AA blastocysts (good quality of both inner cell mass and trophectoderm) are deposited, which is significantly higher than the 45% of Day 3 embryos.
Comparison of clinical data
| norm | single blastocyst transfer | Double cleavage stage embryo transfer |
|---|---|---|
| Clinical pregnancy rate | 62% | 58% |
| live birth rate | 55% | 48% |
| Multiple pregnancy rate | 1.2% | 35% |
| Preterm birth rate (<37 weeks) | 7% | 60% |
RESEARCH SUPPORT: The New England Journal of Medicine (NEJM) 2024 study confirms that the cumulative live birth rate for single blastocyst transfers in women under 35 years of age is comparable to that of double blastocyst transfers, but with an 80% reduction in neonatal intensive care (NICU) admissions.
III.Who must choose single embryo transfer?
- Those with limited uterine conditions
Anatomical abnormalities: deformed uterus such as unicornuate uterus, double uterus, and the risk of uterine rupture in multiple pregnancies is up to 15%.
Scarred uterus: patients with a history of cesarean section have an 8-fold increased risk of uterine rupture in twin pregnancies.
- Those with a weak health foundation
Chronic diseases: diabetic patients have elevated risk of preeclampsia in twin pregnancies up to 40%.
Advanced maternal age: the rate of chromosomal abnormalities in twin pregnancies in women over 38 years old is three times higher than that of singleton pregnancies.
- Those with excellent embryo quality
PGT-A screening embryos: genetically tested aneuploid blastocysts with a single transfer success rate of up to 70%.
Repeated transfer failure history: preferring single embryos with the highest developmental potential to avoid “diversification”.
IV.Cracking the myths: the three major cognitive misunderstandings about single embryo transfer
Myth 1: “The more embryos transferred, the higher the success rate”.
Truth: When the quality of embryos is the same, transferring 2 embryos only increases the pregnancy rate by 10%, but the risk of multiple embryos soars 30 times.
❌ Myth #2: “Frozen embryos are not as healthy as fresh embryos”
Data rebuttal: vitrification freezing technology has resulted in a 98% survival rate for embryo resuscitation, and the live birth rate of freeze-thawed blastocysts is no different from fresh cycles.
❌ Myth #3: “Twin pregnancies are a blessing and the risks are manageable”
Case warning: 29-year-old Lily was forced to terminate her pregnancy at 28 weeks of gestation due to twin pregnancy complicated by HELLP syndrome, and both fetuses were left with cerebral palsy.
V. International Trends: How to Promote Single Embryo Transfer Globally?
- Nordic experience: successful practice under legislative regulation
Sweden has reduced the rate of multiple pregnancies from 30% to 5% by restricting the transfer of only 1 embryo to the first IVF cycle under 35 years of age through legislation.
Result: live birth rate remained stable and medical expenditure on preterm babies was reduced by 230 million Euros/year.
- Technological innovation: the three pillars of single embryo transfer
Time-lapse imaging system: continuous monitoring of embryo development to screen individual embryos for optimal division synchronization.
Artificial Intelligence Prediction Model: Trained by a database of 5000 embryos, the accuracy of predicting quality blastocysts reaches 92%.
Endometrial Tolerance Assay (ERA): accurately locates the transfer window and increases the implantation rate to 68%.
VI. Patient Stories: How Single Embryo Transfer Rewrites Fate
- A wise choice for a high-risk group
Case 1: Sarah, 37 years old (after uterine fibroid surgery), chose single blastocyst transfer and successfully delivered a healthy baby boy, avoiding the risk of uterine rupture.
Case 2: Amy, with polycystic ovary syndrome, after 3 failed double embryo transfers, used PGT-A to screen for single embryos and succeeded the first time.
- Psychological adjustment and decision support
Cognitive Behavioral Therapy (CBT): helps patients overcome “quantity anxiety” and understand the scientific logic of prioritizing quality.
Decision support tool: interactive risk calculator to visualize the probability of complications in multiple pregnancies.
VII. Future directions: technological innovations in single embryo transfer
- Mitochondrial Replenishment Technology
For patients with aging eggs, mitochondria from young donors are injected into embryos to enhance the live birth rate of single embryos to 50% for women over 35 years old.
- Embryo gene editing
CRISPR technology to repair specific genetic defects, which may make the success rate of single embryo transfer exceed 80% in the future.
- Individualized transfer strategy
Based on metabolomics analysis, the optimal culture medium is customized for each embryo to maximize developmental potential.
Conclusion: Single Embryo Transfer – Reshaping the Future of Fertility with Quality
In the field of reproductive medicine, the philosophy of less is more is working wonders. Through precision screening, technological innovation and patient education, single embryo transfers safeguard mother and baby without compromising on success rates. Remember: Fertility is not a numbers game, and a healthy child is far better than a statistically false “double surprise”.