We discovered that the maximal follicle diameter on the trigger day is too high, which might impair the outcome of assisted reproduction in vitro fertilization. Excess follicles may reduce the quality of follicles that can be removed during this cycle of ovarian hyperstimulation, resulting in the formation of a relatively small number of embryos that can be used for transfer and decreasing the possibility of clinical pregnancy and final live birth after embryo transfer. Although in the process of ovulation induction, excluding the patients' own ovulation dysfunction leading to the luteinization of unruptured follicles, it is unusual to have enormous follicles without early removal of follicles, it should nevertheless be avoided as far as feasible.
When hCG is utilized early, the appearance and function of follicles are not completely mature, and the LH receptor on follicular granulosa cells is not rich enough (7), so they cannot react adequately to hCG. According to Rubens fadini et al., hCG may stimulate the meiotic recovery of follicle oocytes with a diameter of 10-12mm and advance to the MII stage. As a result, hCG can hardly affect the growth and development of small follicles, causing follicles to be excreted at the wrong time; or the cumulus complex is not loose enough and close enough to the follicular wall, the egg recovery rate is low, and even affects the maturity of oocytes, affecting the fertilization rate and pregnancy rate. Some research examined the major proteins influencing follicular maturation in follicular fluid from the standpoint of proteomics, and they examined the follicular fluid at various phases (9). It has been discovered that mature oocyte follicular fluid There are changes in the composition of immature oocyte follicular fluid and follicular fluid during ovulation, as shown by the combined action of mature oocytes, cumulus cells, and granulosa cells on the microenvironment (10, 11). The egg misses the optimal period for fertilization, the follicle expands to a certain amount, the oocyte is impacted by endogenous LH and prematurely restarts mitosis, resulting in a change in endometrial receptivity and missing the best time for fertilization and implantation.
Follicular formation must be well-regulated in order to provide highly developing oocytes for fertilization. Many components of ovarian follicular fluid (proteins, cell growth factors, peptide hormones, steroids, and so on) vary dynamically with oocyte growth and development and ultimately have a positive or negative effect in oocyte maturation (12).
The proper hCG injection time is critical for obtaining high-quality eggs (13, 14). There is no single standard for the maximum follicle diameter of the hCG trigger day at the moment. Mehri and colleagues Follicles bigger than 18 mm are thought to have mature oocytes with a high fertilization rate, but tiny follicles have a high aberrant or non-fertilization rate despite the fact that they may still contain mature oocytes (15); Wirleitner et al. Believe that follicles with a diameter of 13–23 mm have the best potential to generate high-quality blastocysts leading to live birth (16); studies have also indicated that in the antagonist regimen, more mature follicles may be obtained when the trigger day is chosen at a diameter of 12–19 mm (17). Nonetheless, it is difficult to uncover meaningful information in current research concerning the influence of maximum follicle diameter on oocyte retrieval result and pregnancy outcome when the greatest follicle diameter on the trigger day exceeds 25 mm. Follicles having a diameter more than 25mm had a detrimental influence on the result of in vitro fertilization in this investigation. Because the follicular fluid of such individuals was not examined for effective components as part of the retrospective study, it was unable to systematically detail the influence of large follicular fluid contents on pregnancy outcome from a micro viewpoint. We think that this is due to follicular over-maturing and alterations in associated proteins and growth hormones, which causes barriers to the maturation of additional oocytes (18). Furthermore, mature oocytes may contain larger quantities of estrogen. High estrogen levels shorten the implantation window and cause abnormal expression of implantation-related genes, including insufficient secretion of endometrium under high estrogen action, asynchronous development of glands and stroma, decreased expression of estrogen and progesterone receptors, and premature expression of pinocytes (19, 20).
On the trigger day, the highest follicle diameter in some individuals included in the trial surpassed 25mm. One cause might be that some patients are elderly. Female fertility declines with age, as does follicular cell activity, resulting in out-of-control follicular growth and development. Wu et al. discovered that granulosa cell proliferation reduces and apoptosis rises in aged women. Early egg retrieval in elderly individuals may (21). Second, some people who are not old have impaired ovarian function. Through clinical observation of non-elderly individuals with impaired ovarian reserve, Wu et al. Also showed that selecting the dominant follicle diameter line of 16 ~ 18 mm as the trigger time may acquire the greatest clinical pregnancy rate (22).