One of the common questions that patients ask about IVF is the difference between doing an embryo transfer on Day 3 or Day 5 following egg pick up. To answer this, we should know a little about the reproduction physiology. When a woman conceives naturally, fertilization occurs in her fallopian tubes. It takes about 3 to 4 days for the fertilized egg to travel through the fallopian tube to the endometrial cavity of the uterus ( mother’s womb). During the transit of the fertilized egg (called a zygote at that stage), the zygote divides into an embryo (by day 2-3) and then further divides to a morula (by day 4) prior to arriving/implanting in the uterus. So, by the time the pregnancy implants in the uterus, it's at a stage of development called a blastocyst on day 5.
Investigations on this field show that blastocyst transfer (day 5) during IVF treatments results in a significantly higher chance of pregnancy compared to an embryo transfer on day 3.
We have routinely been performing blastocyst culture and transfer for many years and observe significantly higher implantation and pregnancy rates as compared to what we see with day 3 embryos. First of all, it could be that longer incubation of embryos in the laboratory allows healthier embryos to grow, while those that are not healthy generally stop growing. This would increase the likelihood that better quality embryos would be chosen and transferred into the patient’s uterus, potentially increasing the chance for pregnancy. Another possible reason is that it more physiologically mimics that which occurs in nature during a spontaneous pregnancy. IVF labs which have poorer techniques and personnel, tend to favour day 3 transfers, as they may not be able to nurture the growing embryos for 5 days. However, if a very limited number of embryos are available on day 3 and no embryo selection is required, then the benefit of a day-5embryo transfer may be limited to the improved synchronization between embryo and endometrium. Because it is obvious that the best conditioned place for the embryos is the mother’s womb itself.
Finally, a clinic’s success with embryo cryopreservation following extended culture should also be carefully considered. We believe that extended culture to day 5 must go hand in hand with an excellent cryopreservation program in order to maximize patient success.
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During the program, to get an appropriate response from the drugs, untimely and irregular effects (e.g. ovulation) of the hormones that your body secretes, have to be blocked. Generally, the drugs which would suppress the hormones are started on the 2nd or 21st day of the menstruation. These drugs are applied subcutaneously (under skin) once a day.
Vaginal ultrasound examinations are performed. Because it provides more detailed information compared to the abdominal ultrasound and saves you from discomfort because full bladder is not necessary. Follicles are liquid-filled sacs which are seen as dark colored, oval shapes under ultrasound and are thought to have oocyte inside. As the lubricant gel used is water-based, it does not have any side effects and does not stain your clothing. 
Hormone levels are traced by obtaining blood samples on certain days before beginning to use ovary stimulants. You will be informed in advance for such examinations.
When the follicle number and size, hormone level and the endometrium reaches the desired level, human corionic gonodotropin (hCG), is injected intramusculary to mature the eggs to trigger ovulation. 36 to 40 hours following the hCG injection, ovulation occurs. In IVF procedure, eggs are retrieved by emptying the follicles prior ovulation. As timing is very important, you have to pay maximum attention to follow the given information about hCG injection. On the hCG injection day, you will be explained and given a form explaining how you should get your injection done at a specific hour after 8 pm.
On the day of oocyte pick-up, please come to the hospital in the morning with your spouse, with empty stomach (avoid eating, drinking and smoking 6 hours before oocyte pick-up).
Not every retrieved egg yield to an embryo. Embryo transfer might be canceled if fertilization failure or inadequate embryo formation occurs. For this reason, you should call us the next day of retrieval and get information about the fertilization. In the following days, appropriately developed embryos will be transferred to the uterus. As this procedure is done as a normal vaginal examination, there is no need for anesthesia. We recommend that you have a light breakfast before you come to the center. Previously decided number of embryos will be transferred into the uterus with a plastic catheter in gynecological examination position. This procedure has to be done with full bladder. You can be discharged following this process, after a short rest. Again your IVF doctor will give you information about ET and the days following it. We recommend a home rest the same day but the following day you can go back to your routine life style.
Pregnancy test will be performed on the 12th day following the ET by detecting beta-hCG hormone level in blood. A pregnancy can also occur despite the bleeding.