Poor embryo transfer technique has been estimated to be responsible for 30% of all IVF failures.
The variables of the embryo transfer procedure include the use of ultrasound guidance, the complexity of the procedure, the type of catheter employed, the technique of loading the embryo, the presence of cervical mucus or blood, the possibility of retaining the embryo with a repeated transfer, the clinician’s experience, and the accurate insertion of the embryo into the uterine cavity. Let’s take a look at each factor.
What is a difficult transfer?
A definition of a difficult embryo transfer has not been agreed. However, research has shown that pregnancy rates decrease with the use of additional manoeuvres during the transfer procedure.
Type of catheter
Soft catheters are better than firm ones. A review of over six thousand IVF cycles showed pregnancy rates were 30% higher with a soft catheter.
Ultrasound guidance
A Cochrane review of over 20 studies including over six thousand women found that live birth and ongoing pregnancy rates were increased for women who had an ultrasound-guided transfer compared with those performed just by clinical touch group. Although the reviewers cautioned that the results were based on low-quality evidence.
Performing the procedure with a full bladder as it makes it easier to negotiate the bend in the cervix.
Embryo placement
Placing the embryo in the mid-uterus has been shown to increase pregnancy rates.
EmbryoGlue
EmbryoGlue is an embryo transfer medium enriched with hyaluronat designed to help the embryo attach to the uterus wall and improve the chances of successful implantation. The HFEA rate EmbryGlue amber as an IVF add-on because there is conflicting evidence from randomised controlled trials (RCTs) to show that it is effective at improving the chances of having a baby for most fertility patients.
Acupuncture
The Cochrane review of acupuncture for embryo transfer concluded that there is not enough evidence to determine whether or not acupuncture can improve the success rate of embryo transfer procedures. However, the review did note that acupuncture may be able to reduce the stress associated with the procedure, which could lead to better outcomes. The review concluded that further studies are needed to determine the true effects of acupuncture on embryo transfer success rates.
Removal of cervical mucous
Another review looked at the removal of cervical mucous prior to embryo transfer. The theory is that the mucous could contain molecules that could interfere with the implantation of the embryo, so its removal could potentially reduce the risk of failure. The review found a few low quality trials which provided very little evidence of an overall benefit of cervical mucus removal before embryo transfer.
Bed Rest
A recent peer-reviewed study published in Human Reproduction Update revealed that an extended period of bed rest (over 20 minutes) directly following an embryo transfer was linked to a 15% reduction in the chances of achieving a clinical pregnancy. Therefore, it is recommended that women should be encouraged to continue their daily activities without delay after the embryo transfer procedure.
Conclusion
In conclusion, poor embryo transfer technique has been estimated to be responsible for 30% of all IVF failures. It is important to take into account all the various factors that can affect the success of an embryo transfer, such as the type of catheter used, ultrasound guidance, the placement of the embryo, the presence of cervical mucous, and the length of bed rest after the procedure. By understanding these variables, fertility clinics can better prepare their patients and increase the chances of a successful outcome.
Sources:
Cohen J. Embryo replacement technology. 31 annual post graduate course. San Francisco, CA: ASRM 1998.
Ultrasound versus ‘clinical touch’ for catheter guidance during embryo transfer in women | Cochrane
Hyaluronate enriched medium (e.g. EmbryoGlue) | HFEA
Acupuncture and assisted conception | Cochrane
Authors
Matt is an NHS Consultant in Newcastle with over ten years of experience. His PhD research into subfertility and miscarriage involved developing a clinical trial and patient engagement.
