Purpose: This clinical study was designed to identify and compare the pregnancy rates of simultaneous program of natural-cycle IVF and cryopreserved-thawed ET (NICE) with those of natural-cycle IVF and cryopreserved-thawed ET.
Methods: All three groups comprised spontaneously ovulating infertile women under the age of 40 and without any male factor present. The NICE program was performed in 36 patients (47 cycles) who had previously undergone IVF-ET resulting in cryopreserved embryos. As control groups, the natural-cycle IVF was performed in 45 patients (80 cycles), and the cryopreserved-thawed ET alone in 29 patients (40 cycles).
Results: The cancellation rate of the initiated cycles prior to ET was 19.1% (9/47) in the NICE group, 23.8% (19/80) in the natural-cycle IVF group, and 2.5% (1/40) in the cryopreserved-thawed ET group. The mean number of embryos transferred was 4.0 +/- 1.1 (2-5) in the NICE group, 1.0 in the natural-cycle IVF group, and 4.2 +/- 1.8 (1-5) in the cryopreserved-thawed ET group. The clinical pregnancy rates per aspiration cycle (32.5%) and per ET cycle (34.2%) in the NICE group were significantly higher than those (14.9, 16.4%) in the natural-cycle IVF group. The clinical and delivered pregnancy rates per ET (34.2, 26.3%) in the NICE group were higher than those (20.5, 15.4%) in the cryopreserved-thawed ET group, without statistical significance.
Conclusions: Since the NICE program results in saving the fresh oocyte for patients participating in cryopreserved-thawed ET, more favorable pregnancy rates may be obtained from NICE cycles in women ovulating normally who had previously undergone IVF-ET with embryo cryopreservation.