Shi-Ling Chen*,, De-Sheng Ye, Xin Chen, Xin-Hong Yang, Hai-Yan Zheng, Yan Tang, Yu-Xia He, and Wei Guo

Human Reproduction, Vol.27, No.5 pp. 1351 1356, 2012 Advanced Access publication on March 14, 2012 doi:10.1093/humrep/des049 ORIGINAL ARTICLE Infertility Circulating luteinizing hormone level after triggering oocyte maturation with GnRH agonist may predict oocyte yield in flexible GnRH antagonist protocol Shi-Ling Chen*,, De-Sheng Ye, Xin Chen, Xin-Hong Yang, Hai-Yan Zheng, Yan Tang, Yu-Xia He, and Wei Guo Center for Reproductive Medicine, Department of Gynecology and Obstetrics, Nanfang Hospital, Southern Medical University, Guangzhou 510515, People s Republic of China *Correspondence address. Tel: +86-20-62787604; Fax: +86-20-87280183; E-mail: chensl_92@163.com Submitted on November 22, 2011; resubmitted on January 19, 2012; accepted on February 1, 2012 background: The use of gonadotrophin-releasing hormone (GnRH) agonist for triggering final oocyte maturation and ovulation can reduce ovarian hyperstimulation syndrome (OHSS) in high-risk patients. LH levels post-trigger with GnRH agonist might be correlated with oocyte yield and maturity. Our aim was to evaluate the relationship between serum LH level at 12-h post-trigger and oocyte yield, maturity and fertilization rate in patients at high risk of OHSS and therefore who were treated with a flexible GnRH antagonist protocol in which final oocyte maturation was triggered with GnRH agonist. methods: In a prospective cohort study, 91 patients at high risk of OHSS were treated with a flexible GnRH antagonist protocol and divided into six groups according to their serum LH levels at 12-h after GnRH agonist administration: 15.0, 15.1 30.0, 30.1 45.0, 45.1 60.0, 60.1 75.0 and.75.0 IU/l. The oocyte yield, maturity, fertilization rate and clinical outcomes for each LH interval were analyzed. results: There was a statistically significant reduction in oocyte yield with a concentration of serum LH 15.0 IU/l (P, 0.05), whereas no statistically significant differences in the oocyte maturity and fertilization rate among the six groups (P. 0.05) were seen. Only 5 out of 91 patients (5.5%) had a serum LH 15.0 IU/l at 12-h post-trigger with GnRH agonist. In addition, no statistically significant difference was seen regarding high-quality embryos, implantation rate, clinical pregnancy rate and early miscarriage between patients with LH 15.0 IU/l and.15.0 IU/l (P. 0.05). conclusions: Serum LH level at 12-h post-trigger with GnRHa,15.0 IU/l is associated with a dramatically lower oocyte yield but not with the oocyte maturity and fertilization rate. Serum LH levels post-trigger with GnRH agonist do not affect clinical outcomes. Key words: GnRH agonist / GnRH antagonist / LH level / oocyte maturation Introduction Ovarian hyperstimulation syndrome (OHSS) is a rare iatrogenic and potentially life-threatening complication during controlled ovarian stimulation. As an alternative to hcg, the use of gonadotrophinreleasing hormone (GnRH) agonist for triggering final oocyte maturation and ovulation can reduce OHSS in patients at high risk of OHSS (Babayof et al., 2006; Engmann et al., 2008; Humaidan et al., 2010). This is due to the short half-life of the elicited endogenous LH and FSH, which results in acute irreversible luteolysis. Moreover, retrieval of more metaphase II (MII) oocytes has been reported after triggering with GnRH agonist compared with hcg (Imoedemhe et al., 1991; Humaidan et al., 2005). This increase may be due to the possibility that the endogenous LH and FSH surge triggered by GnRH agonist are more physiological and the simultaneous FSH surge is known to promote LH receptor formation in luteinizing granulosa cells, nuclear maturation (Zelinski-Wooten et al., 1995; Yding, 2002) and cumulus expansion (Eppig, 1979; Strickland and Beers, 1976). Triggering final oocyte maturation and ovulation with GnRH agonist has been known to be dependent solely on LH activity. Studies on the relationship between an LH surge and oocyte maturation in humans (Seibel et al., 1982) and monkeys (Zelinski-Wooten et al., 1991) These authors contributed equally to this work. & The Author 2012. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved. For Permissions, please email: journals.permissions@oup.com

1352 Chen et al. have suggested that 14 18 h of an LH surge were required to reinitiate meiosis. Furthermore, only 5% of the normal LH surge amplitude is necessary for oocyte maturation, whereas 85% of the surge is required for ovulation in rats (Peluso, 1990). Recently, two patients with polycystic ovarian syndrome (PCOS) were reported to fail in oocyte retrieval post-trigger with GnRH agonist, but a successful recovery was attained using hcg 36 h later (Honnma et al., 2011). In addition, a study demonstrated that an LH level at 12-h post-trigger with GnRHa,52 IU/l was suboptimal while,12 IU/l was clearly inadequate for oocyte yield and maturity (Shapiro et al., 2011b). Given that the duration and profile of gonadotrophin induced by GnRH agonist trigger are different from that of the natural cycle, we hypothesized that failure to trigger oocyte maturation may be due to a shorter duration and/or a lower LH level post-trigger with GnRH agonist. The aim of the present study was to investigate the relationship between serum LH level at 12-h post-trigger with GnRH agonist and oocyte yield, maturity and fertilization rate in patients at high risk of OHSS and treated with a flexible GnRH antagonist protocol for undergoing in vitro fertilization and embryo transfer (IVF-embryo transfer). Materials and Methods Subjects This was a prospective cohort study of all women attending the Center for Reproductive Medicine, Department of Gynecology and Obstetrics, Nanfang Hospital, affiliated with Southern Medical University for IVF and/or ICSI from September 2009 to July 2011. Women at high risk of OHSS who received IVF and/or ICSI treatment with a flexible GnRH antagonist protocol were recruited to participate in this study. This study was approved by the ethics committee of Nanfang Hospital and written informed consent was obtained from each participant. The inclusion criteria for patients at high risk of OHSS were as follows: (i) patients with PCOS (The Rotterdam ESHRE/ASRM-sponsored PCOS Consensus Workshop Group, 2004) or polycystic ovarian morphology on ultrasound (Balen et al., 2003); (ii) patients who previously experienced an ovarian stimulation cycle, with a high response to gonadotrophins. Patients were excluded due to coasting and past ovarian surgery. Ovarian stimulation protocols All patients underwent pretreatment with oral contraceptive pills (OCPs) starting on Day 2 of spontaneous menses of the cycle or induced menses prior to the treatment cycle, after blood tests confirmed the presence of a baseline hormone profile. Ovarian stimulation was initiated on Day 2 of withdrawal bleeding with recombinant FSH (rfsh; Gonal F, Merck Serono, Modugno, Italy) or highly purified FSH (HP-FSH; Lishenbao, Livzon, Guangdong, China). The gonadotrophin started at 112.5 225.0 IU per day for 4 days according to age, body mass index (BMI), antral follicle count (AFC) and previous ovarian response. Thereafter, the dose was adjusted on the basis of ovarian response and serum E 2. Cetrorelix (Cetrotide, Merck Serono, Halle, Germany) of 0.25 mg per day was initiated when at least one of the following criteria was reached: (i) the presence of at least one follicle measuring 14 mm, (ii) serum E 2 600 pg/ml or (iii) serum LH level 10 IU/l (Lainas et al., 2010) and was continued until and including the day of trigger. When at least three follicles reached 17 mm or two follicles reached 18 mm in diameter, and at least one of the following criteria was reached: (i) serum E 2 3500 pg/ml, (ii) 25 follicles measuring 10 mm or (iii) 18 24 follicles measuring 10 mm and serum E 2 3000 pg/ml and,3500 pg/ml, a single bolus of 0.2 mg triptorelin (Diphereline, IPSEN, Signes, France) was administered for triggering final oocyte maturation. Oocytes were retrieved transvaginally 34 38 h after triptorelin administration. Conventional IVF and/or ICSI were performed as indicated. Two or three embryos were transferred on Days 2 3 after oocyte pick-up (OPU). The luteal phase was supported with 60 mg of progesterone in oil and 6 mg of estradiol (Progynova, Schering, Lys lez Lannoy, French), starting on the day of OPU and continuing until 8 weeks of gestation in the presence of a positive hcg test. A single dose of 2000 IU hcg was administered on the day of OPU to supplement corpus luteum function. Hormone measurement Basal values of FSH, LH and E 2 were routinely determined before the initiation of OCPs, ovulation induction and GnRH antagonist. Serum E 2,LH and P were measured on the day of, and approximately at 12 h after, GnRH agonist administration. The serum FSH, LH, E 2 and P concentrations were measured using electrochemiluminescence immunoassay (cobas e601, Roche Diagnostics GmbH, Germany). The inter-assay coefficients of variation (CV) for FSH, LH, E 2 and P were 4.5, 2.2, 4.9 and 4.8%, respectively. The intra-assay CV for FSH, LH, E 2 and P were 2.8, 1.2, 3.3 and 2.9%, respectively. Definition of oocyte yield, maturity and fertilization rate Oocyte yield was defined as the ratio of the total number of collected oocytes to the number of follicles measuring 10 mm on the day of oocyte retrieval. Oocyte maturity was defined as the ratio of MII oocytes to the number of collected oocytes in the patients undergoing with ICSI. Fertilization rate was defined as the ratio of normal fertilized oocytes (2PNs) to the number of oocytes used for fertilization (i.e. the denominator in IVF in calculating fertilization rate is all oocytes recovered, but in ICSI it is calculated using only the number of MII oocytes). Statistical analysis Patients were divided into six groups according to their serum LH levels at 12 h after GnRH agonist administration: 15.0, 15.1 30.0, 30.1 45.0, 45.1 60.0, 60.1 75.0 and.75.0 IU/l. Oocyte yield, maturity and fertilization rate were calculated for each LH interval and assessed for trend analysis. Data were analyzed using Student s t-test and x 2, as appropriate. A P, 0.05 was considered statistically significant. Statistical analysis was performed with the Statistical Package for Social Sciences (SPSS, version 16.0 for Windows). Results There were 220 patients who gave informed consent to participate in the study during their IVF and/or ICSI cycle at our center between September 2009 and July 2011. Of those, 109 patients at high risk of OHSS met the inclusion criteria of GnRH agonist trigger. A total of 18 patients were excluded due to coasting (n ¼ 9) and past ovarian surgery (n ¼ 9; Fig. 1). All patients were treated with a flexible GnRH antagonist protocol and received routine luteal phase support. However, two patients had to postpone the administration of 2000 IU hcg on the day of embryo transfer due to extremely high E 2 levels, and one of them was coasted for 2 days. Both of them developed

GnRH agonist trigger: LH level may predict oocyte yield 1353 Figure 1 Flow chart of patients for the study. GnRHa, GnRH agonist; LH, luteinizing hormone. Table I Baseline characteristics, hormone profiles and laboratory parameters of patients. Parameter n ¼ 91 Age, years 29.3 + 3.6 BMI, kg/m 2 20.8 + 2.2 Duration of infertility, years 4.4 + 2.5 Procedure, % (n) IVF 56.0 (51) IVF/ICSI 20.9 (19) ICSI 23.1 (21) Basal FSH, IU/l 6.0 + 1.3 Basal LH, IU/l 7.0 + 4.0 Basal E 2, pg/ml 43 + 30 E 2 at 12-h post-trigger, pg/ml 5201 + 1943 LH at 12-h post-trigger, IU/l 46.6 + 23.2 P at 12-h post-trigger, ng/ml 8.8 + 4.2 Follicles 10 mm on the day of OPU 27.3 + 7.8 Oocytes retrieved 16.7 + 6.4 Oocyte yield, % (n) 61.1 (1519/2486) Oocyte maturity, ICSI, % (n) 78.3 (318/406) Fertilization rate, % (n) 71.5 (1011/1414) Values are mean + SD or percentage (number), unless otherwise noted. severe OHSS. Thereafter we discontinued supplementing hcg as luteal phase support in later patients. Baseline characteristics, hormone profiles and laboratory parameters of the 91 patients are shown in Table I. The average age and BMI were 29.3 years (range: 20 38 years) and 20.8 kg/m 2 (range: 17.1 27.0 kg/m 2 ), respectively. The mean level of serum LH at 12-h post-trigger was 46.6 + 23.2 IU/l (range: 9.7 151.2 Figure 2 Relationship between serum LH level at 12-h post-trigger with GnRH agonist and oocyte yield (n ¼ 91, A), maturity (ICSI patients, n ¼ 21, B) and fertilization rate (n ¼ 91, C). *P, 0.05 for comparison with previous LH level interval; ^trend analysis using x 2. LH, luteinizing hormone. IU/l). Oocyte maturity was calculated only for patients undergoing ICSI. Oocyte yield, maturity and fertilization rate were 61.1, 78.3 and 71.5%, respectively. The relationships between LH level at 12-h post-trigger and oocyte yield, maturity and fertilization rate are shown in Fig. 2. As shown, there was a statistically significant reduction in oocyte yield with concentrations of serum LH 15.0 IU/l (Fig. 2A). Furthermore, the difference was statistically significant only between the 15.0 and 15.1 30.0 IU/l intervals (38.3 versus 68.8%, P, 0.05; Fig. 2A). These data suggest that a serum LH concentration of 15.0 IU/l at

1354 Chen et al. Table II Baseline characteristics, hormone profiles and laboratory parameters of patients with serum LH level 15.0 IU/l or >15.0 IU/l post-trigger with GnRH agonist. Serum LH Serum LH 15.0IU/l >15.0IU/l (n 5 5) (n 5 86)... Age, years 29.8 + 0.8 29.2 + 3.6 Weight, kg 54.4 + 8.6 52.3 + 6.8 BMI, kg/m 2 21.6 + 2.8 20.7 + 2.1 AFC 28.4 + 6.3 28.5 + 8.1 Basal FSH, IU/l 5.0 + 0.8 6.1 + 1.4 Basal LH, IU/l 3.6 + 1.0 7.0 + 4.0 LH on the day initiated with 3.0 + 1.8* 6.1 + 3.0* gonadotrophin, IU/l LH on the day initiated with 2.0 + 1.4* 5.5 + 3.8* GnRH antagonist, IU/l LH on the day of trigger, 0.7 + 0.5 1.6 + 1.2 IU/l Follicles 10 mm on the 28.2 + 5.8 27.3 + 7.9 day of OPU Oocytes retrieved 10.8 + 4.2* 17.0 + 6.4* Oocyte yield, % (n) 38.3* (54/141) 62.5* (1465/2345) Fertilization rate, % (n) 75.9 (41/54) 71.3 (970/1360) No. of high-quality embryos 3.0 + 2.0 5.6 + 3.6 No. of embryos transferred 2.0 + 0.0 2.2 + 0.4 Values are mean + SD or percentage (number), unless otherwise noted. *P, 0.05. 12-h post-trigger may represent the critical threshold level below which there might be a negative impact on oocyte yield. No significant differences were observed in oocyte maturity or fertilization rate among the groups (Fig. 2B and C). In the 91 patients, only 5 (5.5%) had a serum LH 15.0 IU/l at 12-h post-trigger with GnRH agonist. The LH levels on Day 2 of menses, on the day administered with gonadotrophin, on the day administered with GnRH antagonist and on the trigger day in patients with LH.15.0 IU/l were higher than those with LH 15.0 IU/l; however, only LH levels on the days administered with gonadotrophin and GnRH antagonist were significantly different (Table II). Patients with LH.15.0 IU/l demonstrated significantly more oocytes retrieved and a higher oocyte yield compared with those with LH 15.0 IU/l (Table II). There were no statistically significant differences regarding high-quality embryos and embryos transferred (Table II). Patients with LH level.15.0 IU/l at 12-h post-trigger were further grouped according to whether hcg was supplemented on the day of oocyte retrieval or not. The implantation rate, clinical pregnancy rate and early miscarriage were comparable among the three groups (Table III). Discussion This study shows that GnRH agonist (triptorelin of 0.2 mg) is sufficient for triggering final oocyte maturation in GnRH antagonist protocol Table III Clinical outcomes of patients with serum LH level 15.0IU/l or >15.0IU/l post-trigger with GnRH agonist. Serum LH Serum LH >15.0IU/l 15.0IU/l (n 5 86)... (n 5 5) No hcg hcg added added (n 5 62) (n 5 24)... Implantation 12.5 (1/8) 12.9(16/124) 18.2(10/55) rate, % (n) Clinical 25.0 (1/4) 17.5 (10/57) 25(6/24) pregnancy rate, % (n) No. of early 0/1 0/10 0/6 miscarriage Patients with LH level.15.0 IU/l were grouped according to whether hcg was supplemented on the day of oocyte retrieval or not. Values are percentage (number), unless otherwise noted. cycles. Only 5.5% of 91 patients had a lower serum LH at 12-h post-trigger with GnRH agonist. A serum LH level of 15.0 IU/l at 12-h post-trigger with GnRHa was identified as an appropriate threshold to define an adequate level for oocyte yield. The findings of this study also demonstrate that oocyte maturity, fertilization rate and clinical outcomes were comparable despite the serum LH levels at 12-h post-trigger with GnRH agonist. The correlation between serum LH level at 12-h post-trigger with GnRH agonist and oocyte yield and maturity was assessed recently (Shapiro et al., 2011b). The study showed that LH level at 12-h posttrigger,52.0 IU/l was suboptimal with the risk of submaximal oocyte yield and maturity, while,12.0 IU/l was clearly inadequate and associated with dramatically lower oocyte yield and maturity (Shapiro et al., 2011b). Our study showed that LH levels,15.0 IU/l were inadequate for oocyte yield, which was similar to 12.0 IU/l in the study by Shapiro et al. However, our results do not support that lower LH levels may have a dramatic effect on oocyte maturity. In contrast to the present study, Shapiro et al. used a defined low oocyte yield and maturity combined with a receiver operating characteristic curve analysis to estimate the impact of LH levels on the outcome of oocyte retrieval. We believe that the defined low oocyte and maturity might not be suitable for the assessment, as there is a scarcity of references. Moreover, the definition of oocyte maturity was different between the two studies (the ratio of MII oocytes to the number of oocytes retrieved in the present study versus the ratio of MII oocytes to the number of follicles.10 mm on the trigger day in the study by Shapiro et al.). Oocyte yield but not oocyte maturation or fertilization rate was significantly different between LH.15.0 IU/l and 15.0 IU/l in the present study, which could be explained by different requirements of level and/or duration of gonadotrophin for oocyte maturation and ovulation. As the resumption of meiosis required 14 18 h of an LH surge (Seibel et al., 1982; Zelinski-Wooten et al., 1991), and the threshold level for follicular rupture was higher than that for induction of oocyte maturation (Peluso, 1990), we hypothesize that higher LH levels (.15.0 IU/l in the present study) continuing for.14 18 h

GnRH agonist trigger: LH level may predict oocyte yield 1355 might be required for expanding cumulus cells that lead to ovulation in natural cycles or oocyte retrieval in IVF cycles. However, compared with natural cycles (Zelinski-Wooten et al., 1991) and cycles triggered with hcg, a shorter duration and a lower amount of gonadotrophin were triggered by GnRH agonist (Hoff et al., 1983), in which an effective duration of action might be shortened. Further investigation is required to analyze whether a threshold level and duration of LH level post-trigger are necessary for oocyte yield. The relationship between LH level at 12-h post-trigger and oocyte yield could be used to predict and optimize oocyte yield. In the study by Shapiro et al. (2008), patients at high risk of OHSS received leuprolide and hcg concomitantly on the trigger day in a GnRH antagonist protocol. No OHSS was diagnosed in any patients. The serum LH and hcg on the day post-trigger were 69.1 + 36.5 IU/l and 62.2 + 35.4 IU/l. The average number of oocytes retrieved was 20.4 + 6.0. Interestingly, a patient with LH of 11.9 IU/l and hcg of 40 IU/l 9.6 h post-trigger had 29 oocytes retrieved, 24 of which were MII. The study implies that a low LH level could be compensated by hcg to increase oocyte yield. However, according to the relationship between hcg and OHSS, whether hcg is safe and effective to rescue the low LH in patients at high risk of OHSS requires further investigation. Regarding hcg as the evocation of OHSS, other methods such as exogenous gonadotrophin and repeated GnRH agonist might be substituted for hcg. Repeated injections of GnRH agonist have been reported to increase the duration of LH secretion (LH level was.100 IU/l) up to.14 h (Zelinski-Wooten et al., 1991). Although the prolonged duration is significantly shorter than that of a natural cycle, it might be enough for the ovulation process. Recently a study found that the intrafollicular FSH concentration was significantly higher when an oocyte was retrieved rather than not retrieved despite the use of a stimulation protocol (Rosen et al., 2009). Furthermore, a statistically significant improvement in oocyte recovery with a concomitant FSH/hCG trigger injection, compared with conventional hcg trigger alone in routine GnRH agonist long protocol (Lamb et al., 2011), illustrated that FSH might promote LH receptor formation in luteinizing granulosa cells, nuclear maturation (Zelinski-Wooten et al., 1995; Yding, 2002) and cumulus expansion (Eppig, 1979; Strickland and Beers, 1976). Nevertheless, whether repeated GnRH agonist or an additional FSH bolus administered at the time of trigger in GnRH antagonist protocol can improve oocyte yield requires further investigation. Comparable clinical outcomes between patients with LH.15.0 IU/l and LH 15.0 IU/l suggests that LH levels post-trigger with GnRH agonist may not affect clinical outcomes. The clinical outcomes we obtained in patients with LH.15.0 IU/l post-trigger were consistent with prior studies. These studies showed that supplementing with a low dose of hcg on the day of trigger (Shapiro et al., 2011a) orontheday of oocyte retrieval (Humaidan, 2009) for luteal corpus rescue improved clinical outcomes in a GnRH antagonist protocol with a GnRH agonist trigger in high-risk patients (Humaidan, 2009; Shapiro et al., 2011a). In conclusion, our study shows that a serum LH level at 12-h posttrigger with GnRH agonist,15 IU/l is associated with a dramatically lower oocyte yield but not with changes in oocyte maturity and fertilization rate in GnRH antagonist protocol. Furthermore, serum LH levels post-trigger might not affect the clinical outcomes. Whether additional hcg or FSH or repeated GnRH agonist administration is safe and effective to rescue low LH levels post-trigger with GnRH agonist in patients at high risk of OHSS requires further investigation. Acknowledgements The authors are grateful to Le-Le Wang, Ya-Qin Wu, Chen Luo, Wei-Qing Zhang, Zhuo-Lin Qiu and Jie Yang from the Center for Reproductive Medicine, Department of Gynecology and Obstetrics, Nanfang Hospital for their technical support and valuable suggestions. Authors roles All the authors contributed substantially to the paper. S.-L.C. and D.-S.Y. contributed to the whole conception and clinical design, acquisition of data, analysis and interpretation of data and drafted the article and revised it critically for important intellectual content. X.C., X.-H.Y. and H.-Y.Z. made an effort to control the quality of this clinical trial, and contributed to acquisition of data and analysis of data. Y.T., Y.-X.H. and W.G. contributed to acquisition of data. All the authors revised it critically and approved the final form of manuscript prior to submission. Funding This work was supported by National Key Basic Research Development Project of China (973 Program; 2007CB948104), Comprehensive Strategic Sciences Cooperation Projects of Guangdong Province and Chinese Academy (04020416) and Guangzhou Science and Technology Program Key Projects (11C22120737). Conflict of interest All authors declare that they have no conflict of interest. References Babayof R, Margalioth EJ, Huleihel M, Amash A, Zylber-Haran E, Gal M, Brooks B, Mimoni T, Eldar-Geva T, Serum inhibin A VEGF and TNFalpha levels after triggering oocyte maturation with GnRH agonist compared with HCG in women with polycystic ovaries undergoing IVF treatment: a prospective randomized trial. Hum Reprod 2006; 21:1260 1265. Balen AH, Laven JS, Tan SL, Dewailly D. Ultrasound assessment of the polycystic ovary: international consensus definitions. Hum Reprod Update 2003;9:505 514. Engmann L, DiLuigi A, Schmidt D, Nulsen J, Maier D, Benadiva C. The use of gonadotropin-releasing hormone (GnRH) agonist to induce oocyte maturation after cotreatment with GnRH antagonist in high-risk patients undergoing in vitro fertilization prevents the risk of ovarian hyperstimulation syndrome: a prospective randomized controlled study. Fertil Steril 2008;89:84 91. Eppig JJ. FSH stimulates hyaluronic acid synthesis by oocyte-cumulus cell complexes from mouse preovulatory follicles. Nature 1979; 281:483 484. Hoff JD, Quigley ME, Yen SS. Hormonal dynamics at midcycle: a reevaluation. J Clin Endocrinol Metab 1983;57:792 796. Honnma H, Hashiba Y, Asada Y, Endo T. Failure of triggering oocyte maturation with a GnRH agonist in polycystic ovary syndrome: two case reports. Eur J Obstet Gynecol Reprod Biol 2011;157:239 240. Humaidan P. Luteal phase rescue in high-risk OHSS patients by GnRHa triggering in combination with low-dose HCG: a pilot study. Reprod Biomed Online 2009;18:630 634.

1356 Chen et al. Humaidan P, Bredkjaer HE, Bungum L, Bungum M, Grondahl ML, Westergaard L, Andersen CY. GnRH agonist (buserelin) or hcg for ovulation induction in GnRH antagonist IVF/ICSI cycles: a prospective randomized study. Hum Reprod 2005;20:1213 1220. Humaidan P, Ejdrup BH, Westergaard LG, Yding AC. 1,500 IU human chorionic gonadotropin administered at oocyte retrieval rescues the luteal phase when gonadotropin-releasing hormone agonist is used for ovulation induction: a prospective, randomized, controlled study. Fertil Steril 2010;93:847 854. Imoedemhe DA, Sigue AB, Pacpaco EL, Olazo AB. Stimulation of endogenous surge of luteinizing hormone with gonadotropin-releasing hormone analog after ovarian stimulation for in vitro fertilization. Fertil Steril 1991;55:328 332. Lainas TG, Sfontouris IA, Zorzovilis IZ, Petsas GK, Lainas GT, Alexopoulou E, Kolibianakis EM. Flexible GnRH antagonist protocol versus GnRH agonist long protocol in patients with polycystic ovary syndrome treated for IVF: a prospective randomised controlled trial (RCT). Hum Reprod 2010;25:683 689. Lamb JD, Shen S, McCulloch C, Jalalian L, Cedars MI, Rosen MP. Follicle-stimulating hormone administered at the time of human chorionic gonadotropin trigger improves oocyte developmental competence in in vitro fertilization cycles: a randomized, double-blind, placebo-controlled trial. Fertil Steril 2011;95:1655 1660. Peluso JJ. Role of the amplitude of the gonadotropin surge in the rat. Fertil Steril 1990;53:150 154. Rosen MP, Zamah AM, Shen S, Dobson AT, McCulloch CE, Rinaudo PF, Lamb JD, Cedars MI. The effect of follicular fluid hormones on oocyte recovery after ovarian stimulation: FSH level predicts oocyte recovery. Reprod Biol Endocrinol 2009;7:35. Seibel MM, Smith DM, Levesque L, Borten M, Taymor ML. The temporal relationship between the luteinizing hormone surge and human oocyte maturation. Am J Obstet Gynecol 1982;142:568 572. Shapiro BS, Daneshmand ST, Garner FC, Aguirre M, Thomas S. Gonadotropin-releasing hormone agonist combined with a reduced dose of human chorionic gonadotropin for final oocyte maturation in fresh autologous cycles of in vitro fertilization. Fertil Steril 2008; 90:231 233. Shapiro BS, Daneshmand ST, Garner FC, Aguirre M, Hudson C. Comparison of triggers using leuprolide acetate alone or in combination with low-dose human chorionic gonadotropin. Fertil Steril 2011a;95:2715 2717. Shapiro BS, Daneshmand ST, Restrepo H, Garner FC, Aguirre M, Hudson C. Efficacy of induced luteinizing hormone surge after trigger with gonadotropin-releasing hormone agonist. Fertil Steril 2011b; 95:826 828. Strickland S, Beers WH. Studies on the role of plasminogen activator in ovulation. In vitro response of granulosa cells to gonadotropins, cyclic nucleotides, and prostaglandins. J Biol Chem 1976;251: 5694 5702. The Rotterdam ESHRE/ASRM-sponsored PCOS Consensus Workshop Group. Revised 2003 consensus on diagnostic criteria and long-term health risks related to polycystic ovary syndrome (PCOS). Hum Reprod 2004;19:41 47. Yding AC. Effect of FSH and its different isoforms on maturation of oocytes from pre-ovulatory follicles. Reprod Biomed Online 2002; 5:232 239. Zelinski-Wooten MB, Lanzendorf SE, Wolf DP, Chandrasekher YA, Stouffer RL. Titrating luteinizing hormone surge requirements for ovulatory changes in primate follicles. I. Oocyte maturation and corpus luteum function. J Clin Endocrinol Metab 1991;73:577 583. Zelinski-Wooten MB, Hutchison JS, Hess DL, Wolf DP, Stouffer RL. Follicle stimulating hormone alone supports follicle growth and oocyte development in gonadotrophin-releasing hormone antagonist-treated monkeys. Hum Reprod 1995;10:1658 1666.