3D-Endometrial volume and outcome of cryopreserved embryo replacement cycles

The success of artificial reproductive techniques not only depends on the quality of oocytes and spermatozoa but also on the receptivity of the endometrium. The aim of this study was to assess the value of measurement of endometrial volume by three-dimensional (3D) in comparison to 2D-ultrasound in the prediction of implantation in women having transfer of cryopreserved embryos.

One hundred and eight couples were included in this prospective study. All patients underwent the IVF or ICSI program and had transfer of cryopreserved embryos. Sixty-eight transfers were done in a spontaneous cycle and 40 in an artificial cycle. Endometrial thickness, pattern and three-dimensional volume were measured immediately before embryo transfer.

Twenty clinical pregnancies were achieved (PR 18.5 % per transfer), the PR being similar in spontaneous (22.1 %) and artificial (12.5 %, ns) cycles. Three to five days after ovulation (spontaneous cycles) or after the endometrium reached a thickness of at least 8 mm (artificial cycles), a median of three embryos were replaced. In spontaneous cycles, there were no significant differences in endometrial thickness or volume between pregnant (11.9 mm, 2.9 ml) and non-pregnant women (10.7 mm, 3.4 ml). In artificial cycles, the endometrial volume (3.9 vs. 2.5 ml, p < 0.05), but not endometrial thickness (10.7 vs. 10.2 mm, ns) was significantly higher in pregnant than in non-pregnant women.

In artificial cycles, a low endometrial volume is associated with a poor likelihood of implantation. Endometrial volume measured by 3D-ultrasound is an objective parameter to predict endometrial receptivity.