Minimal stimulation
In this study, minimal stimulation protocol is defined as: an extended
regimen (from day 3 until the day before triggering) of clomiphene
(25-50 mg/d orally) in conjunction with gonadotropin injection starting
on cycle days 3 with 75IU daily. No hypothalamic-pituitary suppression
was performed, and the final maturation of oocytes was induced by a
GnRH-a administration.
When at least one dominating follicle exceeded a mean diameter of 14–18
mm and serum estradiol was 800-1000pmol/L per follicle, 0.1mg of GnRH-a
(Triptorelin acetate 0.10 mg, fertipeptil, Ferring, Milan, Italy)
were given as trigger, and a transvaginal oocyte retrieval followed 36
hours later.
After in vitro fertilization or intracytoplasmic sperm injection
according to the husbands’ semen samples, embryo morphology was assessed
on the third day after oocyte retrieval. All available embryos were
transferred on day 3 after the retrieval. Remaining supernumerary
embryos were vitrified, and no more than 2 embryos were transferred in
subsequent naturally prepared frozen cycles.
Luteal phase support of progesterone or micronized progesterone or
dydrogesterone were used for 2 weeks until the determination of
pregnancy. The serum hCG level was measured by immunofluorescence assay
2 weeks after the embryo transfer.