Oral Contraceptives and Cancer RiskOral contraceptives (OCs) first became available to American women in the early 1960s. A correlation between estrogen and increased risk of breast cancer has sparked continuing controversy about a possible link between OCs and cancer. However, in spite of this concern, the convenience, effectiveness, and reversibility of action of birth control pills (which are popularly known as "the pill") makes them the most popular form of birth control in the United States.
This fact sheet addresses only what is known about OC use and the risk of developing cancer. It does not deal with the most serious side effect of OC use--the increased risk of cardiovascular disease for certain groups of women.
Oral ContraceptivesCurrently, two types of OCs are available in the United States. The most commonly prescribed OC contains two synthetic versions of natural female hormones (estrogen and progesterone) that are similar to the hormones the ovaries normally produce. Estrogen stimulates the growth and development of the uterus at puberty, thickens the endometrium (the inner lining of the uterus) during the first half of the menstrual cycle, and stimulates changes in breast tissue at puberty and childbirth. Two types of synthetic estrogens are used in OCs, ethinyl estradiol and mestranol.
Progesterone, which is produced during the last half of the menstrual cycle, prepares the endometrium to receive the egg. If the egg is fertilized, progesterone secretion continues, preventing release of additional eggs from the ovaries. For this reason, progesterone is called the "pregnancy-supporting" hormone, and scientists believe it to have valuable contraceptive effects. The synthetic progesterone used in OCs is called progestogen or progestin.
The second type of OC available in the United States is called the minipill and contains only a progestogen. The minipill is less effective in preventing pregnancy than the combination pill, so it is prescribed less often.
Because medical research suggests that cancers of the female
reproductive organs sometimes depend on naturally occurring sex
hormones for their development and growth, scientists have been
investigating a possible link between OC use and cancer risk. In the
past 18 years, medical researchers have focused a great deal of
attention on OC users. This scrutiny has produced a wealth of data on
OC use and the development of certain cancers, although results have
not always been consistent.
Oral Contraceptives and
Reprinted from the National Cancer Institute, National Institutes of Health