A woman's body prepares for pregnancy each month. If she does not conceive during the month, she sheds the uterine lining -- which includes menstrual blood that passes through the vagina. The average age for a female to begin menstruating in the United States is at 12 years old, but it may begin anywhere between the ages of 8-15, according to the U.S. Department of Health & Human Services. Women typically have a monthly period until they are between the ages of 45-55 and experience menopause.
For most women, periods last between three to five days. The U.S. Department of Health & Human Services says anywhere from two to seven days is normal. A woman's flow tends to shorten and become more regular with age.
What Moms Can Do about Menstruation
Understanding the menstrual cycle is important for moms trying to conceive. The average cycle length is around 28 days.
Women are believed to be most fertile during ovulation. The menstrual cycle is divided into two parts -- one before ovulation and one after ovulation -- according to Planned Parenthood. This is an overview of the two parts of a 28-day cycle:
Part One: The first day of the cycle is when a woman begins her period (and this will usually last for 3-5 days). During days 7-11, the uterine lining begins to get thick. Then hormones get the egg ready to be released from the ovary. The egg is typically released on day 14, 15, or 16.
Part one usually lasts between 13-20 days, but it varies for different women. An individual woman's regular cycle may also change if she is sick, stressed, or even exercises a lot during the month.
Part 2: The second part of the cycle lasts for 14-16 days in most women. The egg travels down the fallopian tube to the uterus (an egg usually joins with sperm in the fallopian tube). If a fertilized egg reaches the uterus and attaches to the lining, the woman will become pregnant. An egg that has not been fertilized will break apart in the uterus in one or two days. The hormones that could support a pregnancy drop off around day 25 and cause the lining of the uterus to break down. A woman will start her period a few days after that -- starting the cycle over at day one.
Women trying to become pregnant often try to figure out exactly when they will ovulate. Fertility expert Dr. Daniel E. Stein, MD, medical director of the IVF program at the Continuum Reproductive Center at St. Luke's Regional Hospital in New York City, says, "There are multiple ways to figure out when you're ovulating. You can use a basal body temperature chart, you can use a urine ovulation kit, you can count back two weeks from the first day of your next period, or a fertility doctor can use blood tests and ultrasound exams to better time ovulation."
Since a woman usually ovulates two weeks before the first day of their next period, if she expects her next period will start on April 1, she will probably ovulate around March 14.
A woman who believes she has become pregnant should not take a pregnancy test before her period. Dr. Hilda Hutcherson, OB/GYN and professor of Obstetrics and Gynecology at Columbia University in New York, says, "Don't take the pregnancy test until you've missed your period by one day. It just doesn't make sense. There are some tests that will pick up pregnancy before you miss your period, but you just set yourself up for a lot of disappointment if you test before you miss your period. So I tell my patients to wait."
For moms trying to get pregnant, it would be nice if every day were a possible pregnancy day. But that's not necessarily the case. Dr. Stein says a woman will not become pregnant the day after her period.
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