How many Embryos to Transfer?


I wish this were Math and I could just say “Always transfer only ONE Blastocyst”

Truth is 95% of the times we follow the rule of single Blastocyst transfer, but the 5% variation to the rule is what makes Embryology interesting. However, as a rule, we NEVER transfer more than 2 embryo’s to the patient.

Everything about Assisted Reproductive Technology has emerged over the last decade to give better results. From better Stimulation Protocols, to better drugs, better media and  better equipment.  All the advancements we see in ART today are aimed to give us an increase in take home baby rate.

Few years back, in absence of newer and tested protocols and techniques, it was a norm to transfer 3 Day 3 Embryo’s. However, due to availability of better culture media and environment, most of the standard IVF Labs culture the embryo upto Blastocyst (Day 5 embryo) and offer a single Blastocyst transfer to patients.

Q. Why is Blastocyst better than Day 3 Transfers?
The average number of oocytes retrieved during any IVF Cycle is usually 7 to 8. Of these 6 to 7 will fertilize. Of the ones that fertilize, 3 to 4 will be Grade A Day 3 Embryos. Of these only 2 to 3 will reach Blastocyst stage. Hence number of good quality embryos on Day 3 will always be higher than number of good quality Blastocyst on Day 5. Transferring on Blastocyst stage is like Eliminating the bad Embryos Naturally.

Say you had 4 A grade and 2 B grade embryos on Day 3 and you freeze them for two attempts, there is a possibility that you end up freezing both the potential blastocysts in one straw and both the potential non-progressive embryo’s in another because most good embryo’s look the same. And in case you happen to transfer the potential non progressive embryo’s first, you will have no pregnancy in the first attempt.
Q. When is transferring a Day 3 Embryo recommended ?
Situations where number of oocytes retrieved is very less (less than 5) and there is no benefit of extended culture for elimination of extra embryos.
Q. When do you recommend transfer of more than 1 Blastocyst?
When uterine cavity has adhesions or adenoma’s it might be beneficial to transfer two embryo’s to increase the chance of implantation. However this needs to be planned only after considering the BMI, body structure and general health and age of the mother.
Patients often request two embryo’s because they want twins.
Twin gestation has many complications as listed below. Most patients if counselled correctly do understand the risks and opt for a single blastocyst transfer.
Q. What are the risks for twin pregnancies?
When compared with a singleton pregnancy, Twin pregnancies are at an increased risk of early pregnancy loss, preterm delivery leading to low birth weight and immature babies, raised blood sugar levels (Gestational Diabetes) and raised blood pressure during pregnancy (Pregnancy Induced Hypertension or PIH). In short all possible maternal and fetal risks are increased in twin pregnancies as compared to single pregnancies.
Twins are usually delivered by Caesarean section around 37 weeks and most of the times have lower birth weight that singletons. Most twins will need neonatal intensive care for a few days which not only puts them at risk of infections but also adds on to the hospital bill.
Q. What happens if you transfer more than 2 embryo’s at a time?
If all the 3 or 4 embryo’s attach to the uterine wall, you will have triplets or Quadruplets. Most of the Gynaecologist will advise Fetal Reduction of one of the viable fetus. This meaning, you will have to undergo a procedure between 9 to 13 weeks where one of the three fetus will have to be reduced.
Fetal Reduction is an emotionally draining process. For couples who would do anything to get pregnant, just imagine getting pregnant and then having to remove one. Fetal Reduction is also associated with a risk of bleeding and a complete miscarriage. Also, this involves an additional cost of the Fetal Reduction Procedure.
Final Words
Please discuss your Embyo Transfer Plan with your Clinician. Good IVF Clinics will offer you a Single Blastocyst Transfer. Please have faith in the Doctor and Embryologist, they will do whatever is in your best interest.
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