OBJECTIVETo determine the relatively appropriate actuation time for ovarian super-stimulation of IVF-ET by comparing the influences of different down-regulation days of chorionic gonadotrophin releasing hormone agonist (GnRH-a) upon the follicular diameter, endometrial thickness and the levels of follicle- stimulating hormone (FSH) , luteinizing hormone (LH) and estradiol (E2).

METHODSWe adopted the long protocol of GnRH-a down-regulation in the midluteal phase for 42 patients undergoing IVF-ET. According to the time of GnRH-a down-regulation, we divided the patients into a 10 d, a 15 d and an 18 d group, measured their follicular diameters and endometrial thickness by B-mode ultrasonography, detected the levels of FSH, LH and E2 in the blood, and analyzed the influences of different days of GnRH-a down-regulation on the follicular diameter, endometrial thickness and sexual hormone levels. At 1, 7, 10 and 14 d of down-regulation, we compared the levels of FSH and LH in the blood before the injection of GnRH-a with those 2 and 3 h after it.

RESULTSAt 10, 15 and 18 d after down-regulation, the ovarian follicles with the diameter of 3-4 mm accounted for 16.8, 7.09 and 10.38% (P < 0.05, 10 d vs 15 d and 18 d), those with the diameter of 4.5-7.0 mm made up 80.24, 89.55 and 84.62% (P < 0.05, 15 d vs 10 d and 18 d), and those with the diameter of 7.5-10 mm constituted 2.96, 3.36 and 5%, respectively. Endometrial thickness was (7.73 +/- 2.48) mm in the 10 d group, significantly thicker than (5.41 +/- 0.79) mm and (5.24 +/- 0.85) mm in the 15 d and 18 d groups (P < 0.05). The FSH levels in the 10 d, 15 d and 18 d groups were (3.70 +/- 1.10), (3.51 +/- 0.72) and (3.47 +/- 0.61) mIU/ml, the LH levels were (1.23 +/- 1.00), (1.09 +/- 0.47) and (1.22 +/- 0.72) mIU/ml, and the E2 levels were 41.84 +/- 36.81, 32.84 +/- 14.32 and 9.50 +/- 8.23, respectively, with no significant differences among the three groups. At 1, 7, 10 and 14 d of down-regulation, both FSH and LH levels in the blood were increased at 2 and 3 h after GnRH-a injection, most significantly at 1 d (1.87 +/- 1.49 vs 13.33 +/- 7.81 for FSH, 1.06 +/- 1.13 vs 47.40 +/- 29.97 for LH, (P < 0.05).

CONCLUSIONIn the long protocol of ovarian super-stimulation of IVF-ET, endometrial thickness and the levels of FSH, LH and E2 tended to be stable at 10 d of GnRH-a down-regulation. The percentage of the follicles with the diameter of 4.5-7.0 mm was higher at 15 d than at 10 d, but rose no more at 18 d except for an increased number of smaller follicles 3-4 mm in diameter. Therefore, appropriate prolongation of GnRH-a down-regulation can improve the synchronism of follicular development.