Association between the number of oocytes retrieved and cumulative live birth rate in women aged 35–40 years undergoing long GnRH agonist IVF/ICSI cycles

To study the association between the numbers of oocytes retrieved and the cumulative live birth rates (LBR) in women aged 35–40 years undergoing long GnRH agonist IVF/ICSI cycles.

A total of 931 women aged 35–40 years who underwent their first cycle of IVF/ICSI treatment between January 2010 and December 2013 at Nanjing Drum Tower Hospital were identified and reviewed. The main endpoint of this study was the cumulative LBR after one complete oocyte retrieval, which included fresh and all subsequent frozen–thaw embryo transfer cycles. Odds ratios (OR) and 95% confidence interval (CI) for live birth were estimated by multivariate logistic regression analysis. Furthermore, all the women were divided into four groups based on the number of oocytes retrieved: 0–4, 5–9, 10–14 or ≥15 oocytes group. Variables were then compared among groups.

We found that 634 out of the 931 patients (68.1%) achieved at least one live birth. The number of oocytes retrieved was an independent predictive factor for live birth, with OR 1.20 (95% CI 1.15–1.26) when adjusted for age (years), duration of infertility and Gn (gonadotrophin) doses. The cumulative LBR in the four different oocyte groups was 35.6, 68.8, 83.4 and 89.2%, respectively. When the 1–4 oocytes group was issued as a reference, the ORs for cumulative LBR gradually increased to 3.66, 6.74 and 11.77 in other three oocytes groups, respectively. The moderate–severe ovarian hyperstimulation syndrome (OHSS) rate was dramatically increased in the ≥15 oocytes group (6.9%) when compared to that in the 10–14 oocytes group (0.8%), while the cumulative LBR only increased 5.8% (from 83.4 to 89.2%).

The ideal number of oocytes retrieved in women aged 35–40 years is 10–14 oocytes, which achieves a high cumulative LBR while maintaining an acceptable low OHSS rate.