Embryo transfer

Embryos of poorer quality may exhibit fewer cells, blastomeres of unequal size, or varying degrees of fragmentation. Embryo transfer is associated with potential complications. The mucus present within the cervical canal may block the tip of the catheter, causing the embryo to be retained or improperly positioned in the uterus. Additionally, cervical mucus can serve as a source of bacterial contamination of the uterine cavity and adversely affect outcomes. It is best to remove clear or excessive cervical mucus before embryo transfer, but there is no evidence to support the benefit of vigorous cervical lavage.

The presence of blood at the tip of the catheter following embryo transfer indicates trauma to the endocervical or endometrial mucosa and is associated with a decreased pregnancy rate. Embryos that adhere to the outer side of the catheter after transfer may be dislodged or expelled when the catheter is removed. Microscopic examination of the catheter immediately after embryo transfer can identify any remaining embryos, necessitating a second transfer procedure. Embryo transfer catheters exhibit a wide variety of designs. These catheters can be relatively stiff or completely soft. Many of these catheters also have a flexible outer sheath. While stiff catheters and those with a flexible outer sheath are easier to insert, they can increase trauma and uterine contractions compared to soft catheters.

While soft catheters have been shown to yield better results compared to stiff catheters, no definitive superiority has been established for any particular type of catheter. Additionally, the syringes used in conjunction with transfer catheters also exhibit various designs and functional characteristics. Some devices require precise controlled expulsion to prevent sudden ejection of the embryo from the catheter, while others, equipped with a compressible-tipped plunger, can inadvertently cause re-aspiration of the embryos after the release of pressure. Post-transfer injection, after withdrawing the catheter approximately one centimeter into the uterus, may help prevent backward flow of the transfer medium (caused by capillary action).

It is best to minimize uterine contractions during embryo transfer as much as possible. The rate of implantation and pregnancy decreases with increasing frequency of myometrial contractions. Manipulations associated with technically difficult transfers or the use of a cervical tenaculum can stimulate uterine contractions and may cause embryos to be pushed into the fallopian tubes or downward toward the cervix. The presence of large volumes of transfer medium (more than 20-50 microliters) or air above the fluid column may increase the likelihood of embryos exiting the uterus and entering the fallopian tube.

The concentration of protein and the viscosity of the transfer medium do not seem to have a significant impact on the outcome of embryo transfer. Limited evidence suggests that the best results are obtained when the tip of the catheter does not reach the fundus and the transfer is performed approximately 0.5-1 cm below the fundus. Transferring the embryo higher, closer to the fundus, may increase the risk of ectopic pregnancy. On the other hand, transferring the embryo too low may result in implantation in the cervix.

While it’s often recommended for patients to rest in bed for 30 minutes or more after an embryo transfer, there’s no concrete evidence suggesting that this improves outcomes. As a result, patients can typically resume their normal daily activities. Physical activity and diet don’t seem to have a significant impact on the outcome either. Mild, intermittent cramps and bloating are common after embryo transfer. However, if you experience moderate to severe pain, it’s important to consult a healthcare provider to rule out potential infections, ovarian torsion, ovarian hyperstimulation syndrome, or other causes of abdominal pain. The primary goal of embryo transfer is to gently place the embryos into the uterus without causing any trauma. It’s essential to remove any mucus or blood and prevent uterine contractions. A preliminary trial transfer can help identify women who would benefit from cervical dilation before starting treatment. Using a small volume of transfer medium, soft catheters, and ultrasound guidance can optimize the procedure’s success.