Wednesday, May 05, 2010
Embryo transfer versus embryo implantation
Many patients do not understand the difference between embryo transfer and implantation and will often confuse these terms.
Embryo transfer is a simple mechanical process in which the doctor inserts the embryos into the uterus, using a catheter ( a plastic hollow tube).
This is usually an easy procedure which takes about 10 minutes to do. It is done by the doctor, and is usually performed using clinical touch ( where the doctor guides the catheter through the cervix into the uterine cavity with his sense of touch: or with ultrasound guidance).
In some patients ( for example, those with cervical stenosis ( a narrow cervix) or with an angulated cervix, the procedure may be technically challenging, and the catheter may not pass through the cervix easily. There are many ways of solving this problem , based on the difficulty and the doctor's experience and expertise. The doctor may use dilators or special catheter sets, which are designed to help him negotiate the cervical canal; or do the procedure under general anesthesia; or
do a ZIFT, thus bypassing the cervix altogether and transferring the embryos directly into the fallopian tubes.
Implantation, on the other hand, is a biological process , and involves three phases - apposition, adhesion and invasion. This is not in a doctor's control, and while most doctors are very good at making embryos in the IVF lab and then transferring them into the uterus, whether these embryos will finally implant or not is not in anyone's control.
Unfortunately, implantation is not an efficient process, whether done in the bedroom or in the clinic , and only about 30% of apparently perfect embryos will finally become babies. The commonest reason why embryos do not implant is that they have a genetic abnormality , and this is Nature's defense mechanism, to prevent the birth of an abnormal baby. While these defects are often random, they are commoner in older women. This is because the eggs of older women have more genetically abnormalities, because they have "aged" and have genetic defects, which we still cannot screen for efficiently. However, as PGD technology improves, our ability to do so will also improve !
So if your doctors makes good quality embryos and transfer them into your uterus, this means he has done a good job. Now whether these embryos will become babies or not you will find out only after the dreaded 2 week wait !