Absence of Period While Taking Birth Control Pills

Content provided by the Faculty of the Harvard Medical School

Absence of Period While Taking Birth Control Pills

Question:

I'm on Ortho Novum 777-28 and have not had a menstrual cycle for five months. I'm not pregnant. Is that normal and safe for my body?

Answer:

Most women have lighter periods while taking the pill, and in some the flow stops altogether. Light or absent flow is a normal effect of the pill, and it is quite safe. Indeed, many users consider it to be one of the pill's non-contraceptive benefits.

In the first half of a regular menstrual cycle, the ovaries produce only estrogen. Estrogen stimulates growth of the uterine lining (the endometrium). After mid-cycle ovulation, the ovary secretes both estrogen and progesterone. The progesterone blocks estrogen from continuing to stimulate endometrial growth in the second half of the cycle. At the end of the cycle, estrogen and progesterone levels drop, the endometrial lining sheds as the menstrual flow, and the cycle starts again.

In contrast, women on the pill are exposed to both estrogen and progesterone throughout the month. The progesterone dose in the pill is set at a level to have a dominant effect on the endometrium. As a result, the uterine lining grows less than it would if you weren't taking the pill. With less build up of the uterine lining, the menstrual flow is lighter. In some women the lining does not grow at all, so no period occurs. This effect is completely reversible after the pill is discontinued.

Some women are troubled by the lack of at least a light period. They may worry it is a sign of pill failure and pregnancy. Pregnancy testing can be done for reassurance. Some women prefer to try a different pill, one that allows for some flow.

Joan Bengtson, M.D., is assistant professor of obstetrics, gynecology and reproductive biology at Harvard Medical School and a member of the Department of Obstetrics, Gynecology & Reproduction at Brigham and Women's Hospital.

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Last updated:	July 20, 2009

Medical content reviewed by the Faculty of the Harvard Medical School. Harvard Health Publications, Copyright © 2007 by President and Fellows of Harvard College. All rights reserved. Used with permission of StayWell.

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