The fertility cycle in women is controlled by a cascade of events, which are
initiated by protein and steroid hormones. These hormones create signals between the
hypothalamus, the pituitary gland and the ovaries. Oral contraceptives contain an
estrogen-like drug, ethinyl estradiol. It is combined with any of a number of progestin
derivatives. Progestin-only pills are available for women who are breast feeding and
those who are not able to tolerate estrogens. There is also an emergency contraceptive
to prevent pregnancy after unprotected intercourse, called Plan B. One form consists of
two pills, each containing 0.75 mg of levonorgestrel. Mifepristone is a synthetic steroid
that is used for the termination of pregnancy up to the 49th day of gestation. It has been
tested as a morning after pill to prevent pregnancy when taken within 12 hours of
unprotected intercourse. It is also used in combination with another drug called
Gemeprost to terminate pregnancies between weeks 13 and 24. In the USA,
levonorgestrel is the preferred emergency contraceptive. It can prevent a pregnancy up
to 72 hrs after unprotected sex or contraceptive failure. Oxytocin and prostaglandin E2
are also available to induce labor by stimulating uterine contractions. Some women
take hormone replacement therapy, in which a low dose of one or more estrogens
(conjugated equine estrogens) and a progestin are given. Another approach is to
increase the consumption of soybeans and foods made from soybeans (such as soy
milk).
Keywords: Gemeprost, Levonorgestrel, Mifepristone, Progestin, Prostaglandin
E2, Soy.
