PMS vs. Pregnancy: Differences and Similarities

PMS symptoms and signs sometimes mimic those of pregnancy.

Many women have difficulty figuring out if they are pregnant, have PMS, or are about to start their period. The most common signs and symptoms of early pregnancy, PMS, and the start of your period include

• mood swings,
• back pain,
• increased urination, and
• tender breasts.

These three conditions also share other similar signs and symptoms, but there are unique differences between each. Moreover, there are symptoms that only occur if you are pregnant.

The only way to find out if you are pregnant is with a pregnancy test. Home pregnancy test kits are available without a prescription at pharmacies and most grocery stores.

Menstruation (period) is the process of bleeding from the vagina (known as the menstrual period) that occurs at the end of each menstrual cycle. Menstruation begins during puberty and lasts until menopause. Your period starts when the lining of the uterus sheds (approximately every 28 days) because the pregnancy did not occur.

Your menstrual period is due to the normal variation in levels of the hormones estrogen and progesterone, known as the menstrual cycle. Many women experience symptoms including

• cramping,
• bloating,
• breast tenderness, and
• mood changes around the time of the menstrual period.

PMS, or premenstrual syndrome, is a condition characterized by psychological and physical symptoms that develop at some point after you ovulate (which occurs during the middle of the menstrual cycle) and ends when you start your period. Symptoms of PMS can include

• irritability,
• depression,
• crying,
• fatigue,
• bloating,
• acne,
• breast tenderness (mastalgia), and
• appetite changes including food cravings.

While 90% of women are believed to have some symptoms associated with menstruation, true PMS is more severe and likely occurs in 20% to 30% of women.

For many women, the signs and symptoms of early pregnancy can resemble those of her approaching menstrual period or PMS. In fact, it is not possible to tell from early symptoms alone if a woman is pregnant or having symptoms related to her upcoming menstrual period.

The most similar common signs and symptoms that these conditions share include:

1. Headaches: Headaches can be a symptom of pregnancy, but many women also experience headaches or migraines prior to the menstrual period or with PMS.
2. Back pain: This symptom can be if your period is approaching, but it also can be a symptom that you are pregnant.
3. Mood changes (irritability, anxiety, crying spells): Mood changes are common in both PMS and early pregnancy. These changes can include depression, anxiety, irritability, and mood swings.
4. Constipation: The hormone progesterone can lead to digestive disturbances including constipation. Because levels of progesterone rise during the second half of the menstrual cycle, constipation can be present in women with PMS or an approaching menstrual period. Likewise, the hormonal changes of early pregnancy may also cause constipation.
5. Increased urination: You may have increased urination if you are pregnant or you're about to have your period.
6. Breast pain and tenderness: Breast pain, tenderness, breast swelling, or enlargement, can occur in early pregnancy as well as prior to your period. The breasts may feel heavy, sore, or sensitive in both conditions.

1. Bleeding or spotting: Mild spotting (not enough bleeding to soak a pad or tampon) sometimes occurs around the time of implantation of the embryo into the uterus in early pregnancy. This is known as implantation bleeding. This is not the same as the heavy bleeding some women may experience at the beginning of their period.
2. Fatigue: Fatigue is common in women in the early stages of pregnancy, but it also occurs as a sign of PMS in many women. However, the fatigue of PMS generally goes away once the period starts.
3. Food cravings/aversions: Many women experience food cravings or increased appetite prior to the onset of their period. Food cravings and aversions also are typical of pregnancy, although the food cravings of pregnancy are often more specific and intense than during PMS or prior to menstruation.
4. Nausea and or vomiting: Nausea and vomiting are more typical of early pregnancy and are not common symptoms of PMS or an approaching menstrual period. Therefore, if you are pregnant you are more likely to experience these symptoms.
5. Cramping: Abdominal or pelvic cramping and pain occur in many women prior to, or even during their menstrual period. These symptoms often are particularly troublesome for women with PMS. However, some women may have mild cramping in the early stages of pregnancy.

Certain symptoms are more characteristic of early pregnancy and are less likely to occur due to an impending menstrual period or PMS.

1. Missed or late period: The absence of menstruation is the hallmark symptom of pregnancy.
2. Implantation bleeding or cramping: As discussed previously, there may be very mild bleeding and cramping at the time of implantation of the embryo in the uterus during early pregnancy. This is very different from the normal menstrual flow.
3. Vaginal discharge: Increased estrogen production in pregnancy may lead to an increase in milky, white vaginal discharge.
4. Darkening of the areola or nipple: Darkening or enlargement of the areola or nipple can occur as early as a week or two after conception in early pregnancy. It also may develop later in pregnancy. This is not a sign of PMS or approaching menstruation.

The "2-week wait" is a term that has been used to describe the time interval between ovulation and implantation, or the approximate point at which a pregnancy test will yield a definitive answer. Many tests available on the market today are able to determine if you are pregnant, even before the date of the expected menstrual period.