Pregnancy & the Menstrual Cycle

The Menstrual Cycle

Usually lasting for approximately 28 days, your menstrual cycle consists of a series of events and physical changes that occur to prepare your body for pregnancy. Your monthly menstrual cycle is measured in days counting from the first day of your last menstrual period to the first day of your following menstrual period. According to the U.S. Department of Health and Human Services, the adult menstrual cycle ranges in length from 21 to 35 days, whereas the menstrual cycle in teens may last as long as 45 days.

Each month, your menstrual cycle begins with menstruation, the discharge of tissue and blood from your uterus, which usually lasts for three to seven days. The American Pregnancy Association states that at some point in the middle of your menstrual cycle, usually between day 11 and day 21 (11 to 21 days following the beginning of your period), a surge in hormones causes your ovary to release a mature egg (ovulation) which then travels down your fallopian tube, available to be fertilized for 12 to 24 hours. If this egg is not fertilized, it disintegrates, leaving your body during your next period, which marks the end of your menstrual cycle. Each month that you don't get pregnant, this process repeats itself.

In the event that you get pregnant, your menstrual cycle is completely suspended as your body adapts to providing for the needs of the developing fetus. In order for pregnancy to occur, sperm must fertilize your mature egg during the brief time it is available in your fallopian tube. When conception takes place, the fertilized egg travels to your uterus and attaches to the uterine wall, which has already thickened in preparation for the fertilized egg's arrival. This implantation triggers the production of pregnancy hormones, such as progesterone and estrogen, which cause your body's menstrual cycle to halt for the duration of your pregnancy, so your body can care for the unborn baby.

Many women falsely believe that they can experience a menstrual period during pregnancy. According to PregnancyInfo.net, bleeding similar to menstruation may occur during pregnancy but it is not related to your menstrual cycle. Up to 30 percent of women who are pregnant experience vaginal bleeding or spotting during the first trimester of pregnancy that you may mistake for a period, falsely assuming that your body is still going through the menstrual cycle, when in fact the bleeding is caused by other events, such as implantation of the fetus, miscarriage, vaginal irritations or ectopic pregnancy.

Once your pregnancy ends in the birth of your baby, your body requires some time to get back to normal in order for your menstrual cycle to return. Since breastfeeding causes your body to continue to produce hormones that inhibit ovulation, whether or not you breastfeed your baby is the most important factor in determining how soon after pregnancy your menstrual cycle returns. Sally Sago, a midwife with the BabyCenter.Com editorial team, states that your menstrual cycle could return as soon as a month (if bottle feeding) or as late as a year (if breastfeeding) after your pregnancy ends.