Early versus late hCG administration to trigger ovulation in mild stimulated IUI cycles: a randomized clinical trial

To verify non-inferiority of the clinical pregnancy rate of Early hCG administration (leading follicle sizes within 16.0-16.9 mm in diameter) compared to Late hCG administration (leading follicle sizes within 18.0-18.9 mm in diameter).

Prospective randomized trial. Six hundred and twelve infertile women candidates for intrauterine insemination (IUI) received HP-hMG 75 IU/day SC from cycle days 4 to 8 and then as per ovarian response. Ovulation was randomly triggered (hCG 5000 IU, IM) when the leading follicle diameter ranged between either 16.0 and 16.9 mm (Early hCG group, n=227) or 18.0 and 18.9 mm (Late hCG group, n=207) and IUI was performed approximately 36 h later.

Whereas population and sperm characteristics were comparable in both groups, the number of follicles ≥ 14 mm in diameter (P<0.007) and serum estradiol levels (P<0.001) on the day of hCG were lower in the Early versus the Late hCG groups. Clinical (11.9% versus 12.1%) and ongoing (11.0% versus 8.6%) pregnancy rates per randomized women were similar in the two groups and statistical non-inferiority of clinical and ongoing pregnancy rates was demonstrated.

These results suggest that hCG administered when the largest follicle size reaches 16.0-16.9 mm leads to similar clinical and ongoing pregnancy rates as when it reaches 18.0-18.9 mm in IUI cycles.