Occurs in the ovarian follicle of the ovary.
Oocytogenesis is completed in the perinatal period.
A newborn female has all the oocytes she will have and it is about 7 x 10 to the 6th power.
Primary oocytes are arrested in prophase I until ovulation.
Secondary oocytes are arrested in metaphase II until fertilization.
Within minutes of fertilization the ootid cell type appears and becomes an ovum before pronuclei combine to form a zygote.
Maturation of the oocyte takes place within an ovarian follicle.
Women have a finite pool of oocytes that decreases throughout their reproductive years, with fewer than 1000 eggs remaining at the onset of menopause.
Probability of achieving pregnancy in each cycle diminishes as they age because of increasing rates of aneuploidy in association with older oocytes.
Factors associated with accelerated decrease in the number of primordial follicles and early reproductive senescence include: family history of early menopause, smoking, genetic factors, pelvic radiation, ovarian surgery, and the use of chemotherapy.