| BACKGROUND: In 1984, Porter [1]declared at the first time that in the setting of IVF, the use of hypophyseal suppression with Gonadotropin Releasing Hormone agonist (GnRHa) before ovary stimulation would improve the qualities of retrievals and obtain much higher pregnancy rate, following by the inhibited premature LH surge. Then many correlative studies had shown an increase in the number of oocytes obtained, higher fertilization rates, better embryo quality and higher pregnancy rates. In 1997, Damario[2] concluded that OC pretreatment would decrease the cancel rate of high ovarian response, and improve the rate of implantation and pregnancy for the double pituitary suppression. Copperman[3] also advocated that OC pretreatment would get better outcomes in low ovarian response crowd. Indeed, OC has been widely used for many years to IVF/ICSI cycles in normal response women and some investigators expected that it would improve the IVF outcome. Although studies on whether pretreatment of OC prior to GnRHa in women with normal menstrual cycles changed the rates of fertilization and pregnancy were controversial[5-6], the advantages of good time-controlling drived most centers to show much favoritism on it.Objective: This study compares response to gonadotrophin (Gn) stimulation under hypophyseal suppression in subjects with spontaneous ovulation in previous cycles between with or without OC pretreatment. Method: A retrospective analysis was performed on 1668 fresh IVF/ICSI cycles received a long protocol of GnRHa treatment from October 2007 to May 2009. Patients were divided into two groups according to the pretreatment with OC or not: Group OC, prior oral contraceptive and the control, no prior oral contraceptive.Result: The total does of GnRHa and Gn, the start day of ovary stimulation and the duration of stimulation were no differences between the two groups (P>0.05). The number of retrieved oocytes, MⅡoocytes and total embryos were not significantly different between the two groups, neither were the rates of fertilization, cleavage and pregnancy, the incidence of ovarian cyst, and the cycle's cancellation rate for poor ovarian response (P>0.05). But the levels of serum E2 before the ovarian stimulation in Group OC were significant lower than in the control. On the day of HCG injection, there were significant higher serum E2 levels and thinner endometrium in Group OC (P<0.001). In addition, the cancelling rate of fresh embryo-transfers caused by high risks of ovarian hyperstimulation syndrome (OHSS) (>20 oocytes and correlative clinical symptom) in Group OC was significantly higher than in the control(P<0.05). The two groups were respectively divided on the basis of age into 4 layers of≤25 years, 25~30 years, 30~35 years, >35 years(The constituent ratio is no difference between the two groups,χ2=3.006,P=0.391), and the variables of every layer between the two groups were analyzed. The comparison outcomes in the other three layers under 35 years between the 2 groups were similar to the whole subjects, But the serum LH levels of women >35 in group OC were much lower than that of control after suppression (P <0.05), and they needed more dose of Gn (P<0.001) which probably caused by deeper suppressive. The serum E2 levels of women >35 years on the day of HCG injection were lower than younger women but there was no significant difference in these older women between the two groups(P>0.05).Conclusion: Pretreatment with OC prior to pituitary suppression with GnRHa can not decrease the ovarian cyst formation or increase the pregnancy rate. On the contrary, it might cause over suppression, especially in older women.
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