How Things Work: Birth Control Pills

According to research done by the National Center for Health Statistics, 53 percent of women aged 15 to 24 that use forms of pregnancy prevention choose to use birth control pills.

There is more to a birth control pill than just a circle of color. Each pill contains a special ingredient. When it is taken every day, the birth control pill has the power to prevent a woman from becoming pregnant. How can birth control pills possibly prevent the fertilization of an egg?

Normally, pregnancy occurs when an egg in the uterus is fertilized by a man’s sperm. The pill prevents ovulation by fooling the body into believing that it is pregnant.

During menstruation, the pituitary gland secretes follicle-stimulating hormone (FSH) and luteinizing hormones (LH) in response to gonadotropin-releasing hormone (GnRH) from the hypothalamus. FSH stimulates growth of the follicles, the cells in the ovary that release the egg. This in turn stimulates the secretion of the hormone estrogen. As estrogen levels rise, there is an increase in LH concentration, which causes ovulation — the release of the egg. The levels of estrogen and the progesterone hormone rise, which in turn inhibit the secretion of FSH and LH.

The birth control pill contains hormones that work with the body’s natural hormones to prevent pregnancy by putting a stop to ovulation. It suppresses the natural hormones in the body that would stimulate the release of an egg. The most common pill, called the combination pill, consists of the hormones estrogen and progesterone. These synthetic hormones negatively feed back to the pituitary gland and inhibit the normal cyclic production of hormones that stimulate ovulation.

Estrogen stimulates the pituitary gland to produce a hormone called prolactin. Prolactin inhibits the release of GnRH, which halts the secretion of LH and FSH. These hormones are responsible for ovulation, so prolactin effectively prevents the release of the egg. If there are no eggs to be fertilized, pregnancy is impossible. Progesterone thickens the cervical mucus, hindering the movement of sperm, and prevents the uterus’s lining from developing normally, making implantation of an egg very unlikely.

Birth control pills also result in lighter periods due to excess progesterone. The progesterone causes thinner uterine walls and thicker cervical walls, which make it difficult for sperm to travel. Both ovulation and the normal lining of the womb, which is normally meant to prepare for egg and sperm implantation, are inhibited. When menstruation occurs, there is no excess lining to be shed.

In a 28-tablet packet, the first 21 days contain the active pills, or the hormones. If the tablets are arranged in three different colors, each color indicates the different amounts of hormones in each pill. The last seven tablets contain iron or an inactive ingredient. They are not birth control pills and serve the purpose of continuing the cycle of taking a pill each day. Menstruation occurs during the period of these seven days.

There are other types of birth control pills. In a 21-tablet packet, one pill is taken daily for 21 days. There is also a 91-day tablet packet. Another type of birth control is the minipill, which contains no estrogen. It inhibits the egg’s ability to travel through the fallopian tubes, prevents the sperm from traveling up the cervix, and therefore suppresses the sperm’s ability to unite with an egg.

There are many advantages to birth control pills. They greatly decrease menstrual cramps and reduce blood loss and PMS symptoms. Plus, at a young woman’s age, it isn’t time to be worrying about pregnancy. But birth control pills also carry many disadvantages, which include the expenses for the pills, possible side effects of headaches or depression, and having to remember to take the pill every day.

Bottom line: Choose wisely and be safe!