Abstract
This study investigated whether or not the yield of abnormal eggs produced after repeatedly induced ovulation could be reduced by increasing the interval between gonadotrophin (GTH) administrations. Ovulation was induced, in a mouse model, by subcutaneous injection of pregnant mare serum GTH and human chorionic GTH given once (n = 10), twice (n = 10), three times (n = 10) or four times (n = 10) at intervals of 5 days. In 30 further mice, a fifth induction was performed either 5 (n = 10), 10 (n = 10) or 20 days (n = 10) following the fourth injection. Oviducts were examined microscopically, and the eggs were counted and examined for morphological abnormalities. In the mice who had received four GTH treatments, 33.3% (12 of 36) of the eggs were abnormal. After the fifth induced ovulation performed after an interval of 5, 10 or 20 days, the yield of abnormal eggs was 50.0% (five of 10), 23.1% (nine of 39) and 15.2% (seven of 46), respectively. These results indicate that prolongation of the interval between GTH administrations reduced the yield of abnormal eggs produced following repeatedly induced ovulation.