Timing oocyte collection in GnRH agonists down-regulated IVF and ICSI cycles: a randomized clinical trial

The evidence underpinning the timing of an oocyte collection in IVF or ICSI is limited. The aim of this study was to assess the effect of the follicle diameter size of the dominant follicle on ongoing pregnancy rates.

We conducted a randomized controlled trial, including women aged between 18 and 43 years who were scheduled for GnRH agonist down-regulated IVF/ICSI treatment in four assisted conception units. Women were randomized between timing oocyte collection when the leading follicle had a diameter of 22 mm or when the leading follicle had a diameter of 18 mm. The primary end-point was ongoing pregnancy, defined as a viable pregnancy at 12 weeks of gestation.

The trial had major problems with recruiting patients and after the planned 2 years of recruiting only half of the aimed 400 inclusions were obtained. We allocated 97 women to the 22-mm group and 93 women to the 18-mm group. In the 22-mm group more women reached an ongoing pregnancy (37 of 97 women, 38%) compared with the 18-mm group (22 of 93 women, 24%) resulting in a relative risk of 1.6 [95% confidence interval (CI): 1.03-2.5]. In a logistic regression analysis, the timing of oocyte collection, adjusted for female age, IVF/ICSI and centre, was still associated with ongoing pregnancy, although the association was no longer statistically significant (OR: 2.0; 95% CI: 0.96-4.2) CONCLUSIONS: This study suggests that delaying the timing of oocyte collection in IVF or ICSI results in better ongoing pregnancy rates, however, larger studies have to be performed to prove or refute these findings.

ISRCTN24724622.