One often hears the expressed opinion that the BCP suppresses response to ovarian stimulation. This is not the case, provided that the BCP is overlapped with administration of an agonist (e.g. Lupron, Buserelin, Superfact) for several days leading up to the start of menstruation and the initiation of ovarian stimulation cycle with gonadotropin drugs. If the latter precaution is not taken, and the cycle of stimulation is initiated coming directly off the BCP the response will often be blunted and subsequent egg quality could be adversely affected. The explanation for this is that in natural (unstimulated) as well as in cycles stimulated with fertility drugs, the ability of follicles to properly respond to FSH stimulation is dependent on their having developed FSH-responsive receptors . Pre-antral follicles (PAF) do not have such primed FSH receptors and thus cannot respond properly to FSH stimulation with gonadotropins. The acquisition of FSH receptor responsivity requires that the pre-antral follicles be exposed to FSH, for a number of days (5-7) during which time they attain “FSH-responsivity” and are now known as antral follicles (AF). These AF’s are now able to respond properly to stimulation with administered FSH-gonadotropins. In regular menstrual cycles, the rising FSH output from the pituitary gland insures that PAFs convert tor AF’s. The BCP (as well as prolonged administration of estrogen/progesterone) suppresses FSH. This suppression needs to be countered by artificially causing blood FSH levels to rise in order to cause PAF to AF conversion prior to COS commencing, otherwise pre-antral-to –antral follicle conversion will not take place in an orderly fashion, the duration of ovarian stimulation will be prolonged and both follicle and egg development may be compromised. GnRH agonists (e.g. Lupron, Buserelin, Superfact) , cause an immediate surge in release of FSH by the pituitary gland thus causing conversion from PAF to SAF. This is why, women who take a BCP to launch a cycle of COS need to have an overlap of the BCP with an agonist. By overlapping the BCP with an agonist for a few days prior to menstruation the early recruited follicles are able to complete their developmental drive to the AF stage and as such, be ready to respond appropriately to optimal ovarian stimulation. Using this approach, the timing of the initiation of the IVF treatment cycle can readily and safely be regulated and controlled by varying the length of time that the woman is on the BCP.Since optimizing follicular response to COS requires that prior to stimulation with gonadotropins, FSH-induced conversion from PAF to AF’s first be  completed and the BCP suppresses FSH, it follows when it comes to women launching COS coming off a BCP something needs to be done to cause a rise in FSH for 5-7 days prior to menstruation heralding the cycle of CO S.This is where overlapping the BCP with an agonist (e.g. Lupron/Superfact/Buserelin) comes in. The agonist causes FSH to be released by the pituitary gland and if overlapped with the BCP for several days and this will  (within 2-5 days) facilitate PAF to AF conversion…. in time to start COS with the onset of menstruation. Initiating ovarian stimulation in women taking a BCP, without doing this is suboptimal I believe it to be essential regardless of the protocol of COS protocol being contemplated, for women who launching ovarian stimulation coming off a BCP to overlap with an agonist for several days in advance of initiating ovarian stimulation with the onset of menstruation.