Multiple implantation after oocyte donation: A frequent but inefficient event

Objective: To evaluate the natural history of multiple implantation in a donor oocyte program. Design: Retrospective review of clinical pregnancies resulting from donor oocytes with analysis of serial vaginal ultrasound examinations beginning 21 days after embryo transfer. Setting: University of Southern California IVF program (USC-IVF). Main Outcome Measures: Number of implantation sites lost during gestation, furthest development of the gestation, and clinical symptoms of those experiencing loss. Results: Sixty- two of 101 patients (61%) who became pregnant had multiple implantations, 41 (41%) with two sacs, 12 (12%) with three sacs, 6 (6%) with four sacs, and 3 (3%) with five sacs. Overall 28% of implantations sites were lost spontaneously. Rates of loss were similar for multiple implantations. The majority (62%) of these nonviable sacs did not develop beyond a gestational sac. All patients with three or more implantation sites had ongoing pregnancies through the first trimester. The probability of pregnancy loss after visualization of fetal heart motion was 5.7%. Few patients who underwent a natural self reduction of sacs were symptomatic. Conclusions: There is a significant self-reduction in multiple implantation sites in a donor oocyte program. This may obviate the need for a selective reduction procedure. Patients should be followed for up to 10 weeks after ET before committing to a selective reductive procedure.