Embryo transfer is the most crucial step in an IVF cycle. A woman undergoes days of preparation before having an embryo transfer done. Initially the women are stimulated with gonadotropins from the 2nd day of her menstrual cycle, in order to increase the number of eggs that she can produce. When the follicles in the ovary bearing the egg, are mature a trigger in the form of a human chorionic gonadotropin (HCG) is administered. 36 hrs post the trigger the women are ready for an ovum pick up.
After all the days of stimulation and egg pick up, it is time for the embryos to grow and then be transferred back into its natural habitat. Embryo transfer is a process wherein the embryo created by the union of the sperm and the egg, incubating and growing in the incubator of the laboratory is to be transferred to the uterus of the surrogate mother.
It is but natural for women/couples undergoing infertility management to be confused at various stages of their treatment protocol. The major confusion however remains the same among most couples and that is – when should I go in for an embryo transfer? Day 2, day 3, day 5 or even a sequential transfer. A sequential transfer is when the woman has two transfers in the same cycle – one on day 3 and the other on day 5.
The day of embryo transfer is like two sides of a same coin. Each has its own merits and demerits. Many couples after reading medical literature opt for a day 5 blastocyst transfer. On an overview it appears that the blastocyst is a better option, then why the controversy?
Day2/3 embryo transfer
- More embryos to choose from
- Put back embryos as early as possible into the uterus – its natural habitat
- Option of freezing embryos for the next cycle
- Comparable pregnancy rates
Day 5 embryo transfer
- Only the best embryos grow to blastocyst, remaining embryos go redundant
- Better quality embryos can be transferred to the uterus
- Better synchrony between day 5 embryo and the uterine lining
- Higher chances of pregnancy
Sequential transfer
- Better chances of pregnancy as both day 3 and day 5 blastocysts have been transferred
Several research scholars performed randomized, prospective study in regards to the day of embryo transfer and success rate. But it appears from medical literature that postponing the transfer to day 5 has no great advantage as against day 3 transfer. It depends on the number of embryos, quality of embryos on day 3 and endometrium lining.
After discussing the above results, we would say that is indeed a necessity to discuss with the treating infertility specialist as to what is best for that particular cycle. The endometrium lining, thickness and the physical markers may vary in every woman. There is a strict criteria that we follow to choose our surrogate mothers. Only those women with proven fertility and having children of their own are chosen as surrogate mothers. The endometrium lining of these women is different as compared to the infertile patient since they have already conceived before.
The surrogate mother is prepared along with the women receiving gonadotropins so as to synchronize the egg pick up and the embryo transfer. Most women’s’ endometrium is ready for a day 3 embryo transfer. However if there are a greater number of eggs retrieved and the quality of the embryos on day 3 are of grade I, the embryo transfer can be extended to a blastocyst transfer. The treating physician will take a call during day 2/3 post the egg pick in order to establish the correct day of embryo transfer.
Hence it is best to wait till day 3 before any decision is taken with regards to embryo transfer. Keeping in mind the number of eggs retrieved the quality of the sperm and the egg, the quality of the embryo and the endometrium thickness and preparation the right day of embryo transfer can be determined. In doing so there is a slightly higher chance to achieve a pregnancy.
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