It’s rare, but it is possible to become pregnant during your period, especially if your cycle is not regular.

A woman’s menstrual cycle (monthly period) is controlled by changing levels of certain hormones. These hormones travel through the blood. Two hormones, estrogen and progesterone, play a big role in the menstrual cycle.

One type of painful period seems to run in families. Researchers in the 1970s and 1980s discovered higher than average levels of prostaglandin -- fatty acids in the body that act much like hormones -- in the menstrual fluid of women who suffered from cramps.

It's estimated that PMS affects 70 to 80 percent of women in their childbearing years; 30 to 40 percent of women have symptoms severe enough to interfere with daily activities, and 5 to 10 percent have symptoms so severe they're considered disabling.

From conception (fertilization) until after the birth of your child, you and your baby will change every day. To help you understand what is happening, we’ve outlined how pregnancy begins and some of the changes you may notice.

These physical changes often signal that your baby will soon be born -- discharge from your vagina may increase and become thicker; you may notice a pink or brownish discharge called the bloody show; the mucous plug may break down; or you may feel Braxton Hicks contractions (false labor).

Your urinary tract helps to get rid of urine (your body’s liquid waste). The kidneys collect unneeded chemicals and water, making urine. Urine travels through the ureters to the bladder. The bladder fills with urine, holding it until you’re ready to release it.

Your body has a special system built to create and support a growing baby. This is called your reproductive anatomy. Get to know the parts of your body and what they do.

Breasts change over time. Their size and texture may vary with shifts in your body weight. Breasts also change as you go through different stages of your life.

Most breast conditions are noncancerous. But if you notice any breast changes that aren’t normal for you, see your healthcare provider.