Association between the proportion of dominant follicles and oocyte developmental competence

Abstract

Purpose To explore the optimal timing for hCG triggering by investigating the impact of different proportion of dominant follicles on the oocyte developmental competence. Methods One hundred ninety-eight infertile women were divided into three groups according to the proportion of dominant follicles on hCG day: (1) low: <15 % (n=66); (2) middle: 15-27 % (n=66); (3) high: >27 % (n=66). The grouping criteria were the bottom and top tertiles of the proportion of dominant follicles. Results The gonadotropin dosage, duration and maximum follicle diameter in the low proportion group were lower than those in the middle and high proportion groups. Oocyte maturation and the abnormal fertilization rate in the low proportion group were lower than those in the middle and high proportion groups. The normal fertilization rate did not differ among the three groups. The cleavage rate and number of transferable embryos in the low proportion group were significantly higher than those in the high proportion group. The high-quality embryo rate, implantation rate, and pregnancy rate in the low proportion group were significantly higher than those in the middle and high proportion groups.Conclusions A high proportion of dominant follicles are closely associated with impaired oocyte developmental competence and low pregnancy rate. These findings suggest that follicular overgrowth induced by delayed hCG triggering may undermine oocyte developmental competence and the proportion of dominant follicles may be a potential parameters for hCG triggering.

Increasing dominant follicular proportion negatively associated with good clinical outcomes in normal ovarian responders using the depot GnRH agonist protocol: a large-sample retrospective analysis

“…Overgrowth of dominant follicles may lead to oocyte overmaturation, which in turn negatively affects the quality of oocytes and the clinical pregnancy outcome. One study was consistent with our results, and the high-quality embryo rate, pregnancy rate, and implantation rate were significantly higher in the low proportion group (≥ 18 mm follicle divided by the total number of follicles, low proportion: < 15%; middle proportion: 15–27%; high proportion: > 27% in the short GnRH-a long protocol) [ 8 ]. In two other randomised controlled trials of GnRH antagonist cycles, follicle size was enlarged by delaying HCG administration for one or two days after three follicles ≥ 17 mm.…”

“…Oocytes derived from large follicles (14−21 mm; mean diameter: 19.1 ± 2.1 mm) seem to be more inclined to form high-quality embryos in the GnRH antagonist protocol [ 17 ]. Therefore, in practice, the HCG trigger is typically delayed with the aim of stimulating more follicle growth and obtaining as many mature oocytes as possible [ 8 ]. However, a previous study reported that oocytes in oversized follicles may decrease the quality and recovery of oocytes [ 5 ].…”

“…To date, there is no universal criteria for the optimal HCG trigger time [ 1 , 2 , 4 , 5 ]. The common standard in most reproductive centres is to trigger when there exist at least three follicles ≥ 17 mm or at least two follicles ≥ 18 mm [ 1 , 2 , 6 – 8 ]. However, triggering is typically delayed in the expectation of obtaining more mature follicles in practice.…”

“…Ectors et al suggested that delaying the HCG trigger allows for larger follicle growth and may result in more mature oocytes, and this may have a positive impact on clinical outcomes [ 9 ]. However, several studies have shown that delayed oocyte retrieval does not increase the number of mature oocytes nor the pregnancy rate, but it may instead compromise embryo quality [ 8 ]. Confusingly, some studies have found that there is no difference in the oocyte maturation rate and the fertilisation rate between large and small follicles (10−14 mm; 15−19 mm; 20 + mm) [ 10 ]; (< 16 mm; ≥ 16 mm) [ 11 ].…”

“…During COH, follicle growth is often asynchronous. Hence, we need to focus on the development of target follicle cohort, not just a few leading follicles [ 8 ]. The proportion of ≥ 17 mm follicles was used to assess the trigger time of the GnRH antagonist protocol, and this reflected the development of the follicle cohort and contributed to more high-quality oocytes and higher pregnancy rates [ 5 ].…”