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

ObjectivesTo 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).Study designProspective 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.ResultsWhereas 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.ConclusionThese 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.