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Embryo transfer: the final stage of the IVF procedure

Nowadays, more and more women are trying to have a child through assisted reproduction. The final stage before the IVF procedure is complete is the embryo transfer. Read on to find more about how it is performed.

Trial embryo transfers

Embryo transfer is the last step in an IVF attempt but at the same time it is the most delicate stage of the entire procedure. It is known that success rates are higher if the embryo transfer is smooth. Blood in the embryo transfer catheter automatically reduces success rates; that is why “soft” catheters yield the best results. What matters is not to cause any pain, which will trigger uterine contractions. These contractions are usually caused when the catheter touches the base of the uterus; this causes the release of prostaglandins and oxytocin.

There are several techniques available for restricting the level of difficulty as well as blood loss in embryo transfers.  Trial embryo transfers are performed so that we may know what to anticipate and choose the appropriate catheter. These trials are usually carried out before ovulation stimulation or just before the actual embryo transfer. Some IVF centres perform trial embryo transfers at both stages mentioned above. If the trial reveals that the cervix is particularly narrow, then we can opt to open the cervix with dilators before IVF. We can also place a stitch on the cervix during egg retrieval to achieve gentle traction during the embryo transfer. In published comparative studies, the use of trial embryo transfer has shown higher success rates.

Ultrasound guidance

Another common dilemma involves ultrasound guidance during embryo transfer. Ultrasound guidance is indeed very helpful in making sure that the catheter does not touch the base of the uterus and that no contractions are caused. It is also very useful in cases where fibroids are hindering the procedure. Moreover, having a full bladder for ultrasound screening also allows a direct approach to the uterus through the cervical canal. Even today, many colleagues perform embryo transfers without ultrasound guidance while others proceed with embryo transfers at a specific distance of 6 – 6.5 cm from the external cervical os. Many studies have compared the ultrasound-assisted embryo transfer to the blind approach and have shown that the first approach is superior. However, no definite conclusions can be drawn from these studies.

Embryo transfer is usually performed without anesthesia, while cervical mucus is removed in most cases to avoid catheter obstruction that hinders the transfer. Embryos are placed at a 5 – 10 cm distance from the base of the uterus. However, many recent studies support that an even greater distance from the base will contribute towards highest success rates. After the embryos are delivered inside the uterine cavity, the operator should keep pressing on the syringe so that embryos are not withdrawn into the catheter. The catheter should be removed slowly to avoid vacuum… the only thing to do after that is hope for the best!