Birth control pill - series

Normal female anatomy

Normal female anatomy

The internal female reproductive organs include the uterus, ovaries, cervix, and vagina. These organs are necessary to produce a successful pregnancy. To prevent pregnancy, birth control pills affect how these organs function.

FSH and LH from pituitary gland

FSH and LH from pituitary gland

Follicle stimulating hormone (FSH) and luteinizing hormone (LH) travel through the bloodstream and stimulate the ovary into producing a ripe egg ready for fertilization by sperm during a normal ovulation cycle.

Release of estrogen

Release of estrogen

During a normal menstrual cycle, hormones stimulate the ovary, causing an egg to ripen. The uterine lining thickens, preparing itself for implantation of a fertilized egg, and the cervical mucus thins to help sperm reach the egg.

Release of LH

Release of LH

Changing levels of estrogen in the body causes the pituitary gland to release LH and FSH, stimulating the ovary to produce a ripe egg.

Birth control pill

Birth control pill

The steady low levels of estrogen in birth control pills suppress FSH and LH, "fooling" the pituitary gland into thinking a woman is pregnant. Ovulation will then not occur, therefore preventing pregnancy.

Progestin in pill

Progestin in pill

The progesterone in birth control pills also creates a thick cervical mucus, making it difficult for sperm to reach the uterus. It also impedes an egg from attaching itself to the uterine lining (endometrium) because of changes in the cellular structure of the lining.

Version Info

  • Last Reviewed on 05/21/2012
  • Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital.

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This page was last updated: September 18, 2013

         
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