Objective: To study prospectively the fate of oocytes collected from the follicular aspirate and subsequent flushes during transvaginal ultrasound directed oocyte recovery for in-vitro fertilization (IVF).
Setting: A tertiary referral assisted conception centre.
Subjects: 100 consecutive patients undergoing 100 cycles of IVF. Four patients were withdrawn because their embryos were electively cryopreserved. Therefore 96 cycles were studied.
Main outcome measures: The oocyte recovery rate, viability, fertilization and cleavage rates and outcome of embryos generated from oocytes that were obtained from either the initial aspirate (A1), dead space in the collecting system (A2) or the first two 2 ml flushes (F1 and F2) were compared.
Results: The overall oocyte recovery rate was 87.8%. Of the 1046 oocytes collected, 40.3% were from A1, 41.3% from A2, 13.7% from F1 and 4.7% from F2. There were comparable numbers of viable and fertilized oocytes and cleaved, transferred and frozen embryos in tubes A1 and A2 but all these parameters were significantly lower in tubes F1 and F2 (P < 0.0001). All these parameters were also significantly higher in F1 compared with F2 (P < 0.001), except for the number of embryos frozen, in which there was no difference. The overall pregnancy rate per cycle was 28.1% and the pregnancy rate per embryo transfer was 31.0%. There were no pregnancies in any of the cycles in which embryos originating from F2 were transferred, nor were there pregnancies in cycles in which only embryos from F1 were transferred.
Conclusion: Follicular aspiration together with one 2 ml flush maximises the recovery of oocytes that will result in pregnancies.