A period (menstruation) is the time in a woman or girl's monthly cycle in which her unfertilized egg leaves her body, along with blood and uterine tissue lining (endometrium). This normally takes about five days. Periods usually first begin (menarche) at or around age 12 in the US. They may begin between the ages of 10 and 15, though some may also start sooner or later than this. A period begins Day 1 of the menstrual cycle.
The menstrual cycle is the process by which your body prepares an egg for fertilization, and also the period in time when your body removes the egg to prepare for the next egg. This is sometimes called a "monthly cycle," and while 28 days is an average menstrual cycle length, it can range from about 24 days to 34 days.
Menstrual Cycle Timeline (approximated)
- Day 1: Your menstrual cycle begins with the start of your period. The tissue lining around your uterus (endometrium) breaks down and an unfertilized egg begins to leave through your vagina along with blood. The bleeding of a period usually lasts 4-8 days, averaging 5 days for US women.
- Day 5: Your estrogen levels rise once bleeding has stopped, and this does several things. These include:
- The lining of your uterus thickens, preparing it for a new egg.
- Ovarian sacs that contain eggs grow and mature, preparing one for ovulation.
- Ovulation: Starting around day 12-14, an egg releases from your ovary. On this day, and up to three days prior, you are most likely to become pregnant if you have sex. There are subtle ways to help detect that you are ovulating, including body temperature and urine tests. If the egg is not fertilized, the cycle begins again with hormones that tell your uterine lining to break down again.
Many women know if they have a late period, and some keep a calendar to make sure. A late period can turn into a missed period if pregnancy has occurred. But it can also be very normal because women's periods can develop at unpredictable intervals.
A woman's body might offer several clues that she is pregnant. There are also tests available that offer more conclusive proof.
Missed periods are often the first clue that you have become pregnant. But you might continue to have lighter and briefer spotting in some cases.
Your body makes more of the hormone progesterone for the first 13 weeks of pregnancy, which can make you feel tired and sluggish.
When a fertilized egg reaches your uterine wall (about 6-12 days after conception), very light bleeding called "spotting" can sometimes result. Some women also experience cramps at this time.
Your breasts may be tender, swollen, and sore, with a feeling of fullness, as early as one to two weeks after conception.
Some women are nauseous, and might even experience vomiting between weeks two and 14 of pregnancy. This is called morning sickness, and while it is often worse in the morning, this sickness can occur at any time of the day.
You may need to pee more frequently starting at 6-8 weeks of pregnancy. This need to urinate more frequently can last the duration of the pregnancy.
Some women experience mild headaches caused by hormones and blood flow even before their period is missed.
There are both at-home tests and blood tests available to determine if pregnancy has occurred. Both are considered safe methods of detecting pregnancy.
- At-home tests: These test your urine for a pregnancy hormone called hCG. At-home tests are easy, quick, and convenient. However, they are not able to detect pregnancy as early as blood tests. They are most accurate if you wait one week after a missed period to use them.
- Blood tests: Blood tests require a visit to your doctor. But they can detect pregnancy much earlier than at-home tests.
A missed period without pregnancy does not necessarily need medical treatment. However, you should visit the doctor if:
- Your cycle has stopped (despite being regular before).
- You've had unexpected bleeding.
- Your last period was more than 90 days ago.
- Your periods are regularly more than 35 days apart (oligomenorrhea).
- Your periods become unusually heavy, painful, or long lasting, or you bleed between periods.
Depending on your diagnosis, your doctor might recommend lifestyle changes or medication such as birth control hormone therapy.
Late and missed periods can have many causes other than pregnancy. These include:
- Medications, including some anti-epileptics and antipsychotics
- Uncontrolled diabetes
- Medical conditions such as anorexia, bulimia, hyperprolactinemia, PCOS (polycystic ovary syndrome), and premature ovarian failure.
See your doctor if you have any questions about late and/or missed periods.
IMAGES PROVIDED BY:
- NIH: "About Menstruation." Jan. 31, 2017.
- Office on Women's Health: "Knowing if you are pregnant."
- Office of Women's Health: "Prenatal Care and Tests." Jan. 30, 2019.
- PennMedicine: "Irregular Periods: Why Is My Period Late?" Nov. 2, 2020.