Day 5 Embryo Transfer: IVF
• What Is Blastocyst Transfer?
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|What Is Blastocyst Transfer?
A blastocyst is an embryo that has grown for 5 or 6 days after fertilization. A 3 day embryo is typically only about 6 to 8 cells in size. A blastocyst has divided into far more cells, and it is even possible to tell which are the baby and which will become the placenta.
Only 30 to 50 percent of embryos created in a lab survive to blastocyst stage. Waiting to know which ones these are before transfer can improve the pregnancy success rate. Once transferred, a blastocyst, like any embryo, must successfully stick to the wall of the womb (implantation) for pregnancy to occur.
The procedure is similar to normal embryo transfer. But instead of being transferred after 2 to 3 days, they are transferred to the womb after 5 to 6 days.
Initial studies revealed that embryos transferred at day 5 have a 50 percent implantation rate, compared to 30 percent in those transferred at day 3. These studies assume the patient has a good prognosis for IVF - that is, 10 or more follicles at least 12 mm large on the day of receiving hCG gonadotropin injection. However trials with mixed prognosis patients have yielded conflicting results. An analysis of 16 trials involving over a 1,000 2-3 day transfers and 1,000 5-7 transfers observed no difference in live birth rate. Nor, surprisingly, was the overall miscarriage or multiple pregnancy rates any different. It should be noted however, that women with a good prognosis for IVF still did better.
On average it takes 3 IVF cycles to bring about one live-birth (in other words, the first 2 attempts fail). Many fertility clinics now offer blastocyst transfer to improve the chance of a live-birth in the first cycle. This is particularly useful for younger women who have a good prognosis of IVF. See also: IVF success rates.
Blastocyst transfer is more complicated than traditional 3 day embryo transfer. Older embryos require all sorts of things to keep up with their nutritional needs. For this reason, many clinics find it too difficult to grow enough blastocyst to transfer. The danger is, if you wait for your embryos to grow into blastocysts, you may end up with nothing to transfer. The embryologist advising your consultant may consider it safer to transfer a 2 or 3 day embryo than risk postponing transfer to day 5 or 6.
The second problem with blastocysts is that by the time of transfer they are already hatching out of their shell. This increases the risk of a blastocyst splitting in two, becoming identical twins. Identical twins are much more problematic than fraternal twins. Identical twins share the same placenta and sac and there is a risk that one twin will get more nutrients than the other (twin-twin transfusion syndrome, see pregnant with twins). The incidence of umbilical cord accidents is also higher. You are 4 to 5 times more likely to have identical twins undergoing blastocyst transfer. For this reason, some fertility centers only offer the procedure to women who have had several failed IVF cycles.
Many clinics do not charge extra for a 5 day transfer compared to a 3 day transfer.
On my first IVF I had a 5 day blastocyst with a fresh transfer. I tested positive for pregnancy but miscarried at week 5. On my second 5 day blastocyst (frozen), I was positive and am now 7 months pregnant. Fingers crossed!
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