Anatomical causes of difficult embryo transfer during in vitro fertilization.

Objectives: Identify, define and validate through statistical analysis the anatomical causes of difficult embryo transfers (ET).

Materials And Methods: This observational study, carried out in 306 IVF candidates, compared the frequency of anatomical anomalies of the uterus and cervix in women who underwent an easy ET with that in women who underwent a difficult ET. Anatomical anomalies were detected during an assessment of the cervix and uterus including transvaginal ultrasound, hysteroscopy and a mock transfer. Ease of ET was determined during the actual transfer procedure.

Results: An easy ET was achieved in 151 patients, whereas difficulties occurred in 155 patients, among whom 55 patients underwent a "very difficult" ET. The most common anatomical characteristics associated with difficult ET were abnormal crypts in the cervical canal (86%) and tortuosity of the cervical canal (68%). Less frequent causes included: internal os contractions (28%) and pronounced anteversion of the uterus (26%). Very difficult ETs were associated with the presence of several causes.

Conclusions: ET is the clinical step that has the most effect on IVF outcome. Difficult transfers are associated with a fall in pregnancy rates. The anatomical causes of difficult transfer identified in this study led to major changes in transfer procedure in our department and to the development of more adapted catheters.