Premenstrual syndrome causes several symptoms that closely resemble those of early pregnancy. As a result, some women have difficulty determining if they are pregnant or if their period is about to start.
Symptoms of both premenstrual syndrome (PMS) and pregnancy can vary from person to person, but they often include tenderness in the breasts, cramping, and changes in mood.
In this article, we compare the symptoms of PMS with those of early pregnancy and explore the differences between the two.
Symptoms common to both PMS and pregnancy include:
Changes in mood
Feeling irritable, anxious, or sad, or having crying spells, are common in both early pregnancy and the days leading up to a period.
These symptoms of PMS typically disappear once menstruation begins. However, if mood changes persist and a person misses their period, this may suggest pregnancy.
Persistent feelings of sadness can indicate depression. See a doctor if low moods last for 2 weeks or more.
Hormonal changes are a common cause of constipation in women. The fluctuations can slow down bowel movements.
Research suggests that constipation affects up to 38 percent of women during pregnancy, but it also affects many women just before their periods.
Pregnant women are most likely to have constipation in the first two trimesters, while women with PMS-related bowel problems typically experience relief after their periods begin.
Breast pain and tenderness
Breast changes are a common symptom of both PMS and early pregnancy. The changes can include:
- bumpy breast tissue
The severity of these symptoms varies among individuals.
However, in people with PMS, breast-related symptoms are usually most significant just before a menstrual period, and they typically get better during the period or just after it ends.
In early pregnancy, the breasts may feel particularly tender to the touch, and they often get heavier. The area around the nipple may sting or feel sore. Some women also develop more noticeable blue veins near the surface of the breasts.
Breast symptoms during pregnancy begin 1 or 2 weeks after conception and may persist until childbirth.
For women with heavy periods, excessive tiredness can last throughout the period. It may also be a sign of iron-deficiency anemia.
Fatigue is also a common symptom of early pregnancy. It often persists throughout the first trimester, and some women feel tired for the full 9 months. Difficulty sleeping and frequent nighttime urination can make pregnancy fatigue worse.
Bleeding or spotting
Light spotting or bleeding can occur in early pregnancy. This is called implantation bleeding, and it typically occurs 10–14 days after fertilization.
Many women do not experience implantation bleeding. Others may not notice it. It is much lighter than menstruation.
PMS does not typically cause spotting, although a period can be very light on the first day. Usually, menstrual bleeding lasts for 4 or 5 days, and it causes more significant blood loss than the spotting of implantation.
Cramping is common in both PMS and early pregnancy. Early pregnancy cramps are similar to menstrual cramps, but they can occur lower down in the stomach.
These cramps may persist for weeks or months during pregnancy, as the embryo implants and the uterus stretches.
Headaches and back pain
Changes in appetite
Increased appetite and food cravings are common symptoms of pregnancy, but they can also occur with PMS.
Many people with PMS experience increased appetite and cravings for sweet or fatty foods, or carbohydrate-rich meals. Changes in the hormones estrogen and progesterone likely influence cravings just before a period.
Research indicates that 50–90 percent of pregnant women in the United States have cravings.
Many crave specific foods and have aversions to others, finding their sight or smell deeply unpleasant. Food aversions are much less common in people with PMS.
Some pregnant women crave non-food items, such as ice or dirt. The medical term for this phenomenon is pica. Anyone with pica should speak to a doctor.
Some symptoms are more likely to indicate early pregnancy than an impending period. However, a person can only be sure by taking a home pregnancy test or visiting a doctor.
Symptoms that are likelier to signal pregnancy include:
A missed period
Missing a period is one of the most obvious signs of pregnancy. If a period is 1 week late and pregnancy is a possibility, take a pregnancy test.
Many tests are highly sensitive and can detect pregnancy hormones several days before a missed period.
However, there can be many other reasons for a missed or late period, such as:
- low body weight
- polycystic ovary syndrome
- going on or off birth control, or switching methods
- having a medical condition, such as thyroid disease or diabetes
While mild digestive discomfort can occur just before a menstrual period, nausea and vomiting are not typical PMS symptoms.
Typically, these symptoms subside by the second trimester, but some women experience nausea throughout pregnancy.
Although breast changes can occur during both PMS and pregnancy, changes to the nipples rarely happen before a period.
If the areola, the colored area around the nipple, gets darker or larger, this can suggest pregnancy. These changes can occur as early as 1 or 2 weeks after conception.
Women who suspect that they are pregnant should take a home pregnancy test. If the result is positive, make an appointment with a doctor to confirm the pregnancy and plan the next steps.
If the test is negative, but no period occurs within 1 or 2 weeks of when it was due, it is also a good idea to see a doctor.
The doctor can help determine the reason for a late or missed period and recommend treatment options. They can also address concerns about any unusual symptoms.