Medication Protocol
All the subjects received a standardized long-term protocol in
mid-luteal phase or gonadotropin-releasing–hormone (GnRH) antagonist
regimen for ovarian stimulation. For long-term protocol, GnRH agonist
(GnRHa) was used to downregulate the function of the pituitary gland on
day 21 of the previous menstrual cycle. A dose of recombinant FSH
ranging from 75 to 225 IU was initiated after down-regulation. As for
GnRH antagonist regimen, recombinant FSH at a dose of 75 to 225 IU was
administered on day 3 of the menstrual cycle. GnRH antagonist at a dose
of 0.25mg daily was initiated when at least one follicle was 12 mm or
more in the mean diameter. For all two protocols, urinary human
chorionic gonadotropin (hCG) at a dose of 4000 to 8000IU was
intramuscularly injected when at least two dominant follicles reached
18–20 mm in diameter and oocyte retrieval was performed 36–48 h later.
50ml follicular fluid was collected after oocyte retrieval.