The objective of this study is to evaluate the efficacy of embryo transfer procedure guided by transvaginal ultrasound versus abdominal ultrasound in recipients of oocytes as well as the advantages and disadvantages of the new technique.

Inclusion Criteria:

• Oocyte recipients.
• Uterus without previously detected anomalies.
• Patients able to understand the study requirements who want to participate during all its duration and that have signed the informed consent.

Exclusion Criteria:

• Turner syndrome, Black race (significantly lower implantational rates)