Perimenopause or Pregnancy?

Hot flashes, brain fog, weight gain, and changes in mood are common symptoms experienced during pregnancy. However, these can also be signs that a woman has entered the menopause transition at the first phase known as perimenopause. 

For most women, perimenopause starts between the ages of 45 and 55, lasting an average of 4 years before the body progresses into the menopausal stage.⁽¹⁾⁽²⁾ It’s during this time that women begin to experience irregular periods, which is another potential sign of pregnancy. Because there is no set age at which the menopause transition begins for everyone, how can women tell the difference between perimenopause and pregnancy? While they may share certain symptoms, this article will explore the different ways in which perimenopause and pregnancy affect the body.

Perimenopause vs. Pregnancy

Both perimenopause and pregnancy can cause hormone fluctuations, resulting in significant physiological changes. Here are some of the changes women can expect during perimenopause and pregnancy.

Changes in the Body During Perimenopause

Perimenopause begins when women start to experience irregularities in their menstrual cycle and ends 1 year after their last period. This signals the start of menopause, when women can no longer conceive. In early perimenopause, women may occasionally miss a period. During late perimenopause, however, the absence of menstruation may last up to 60 days.⁽²⁾ 

Vasomotor symptoms are common during late perimenopause, with research showing that up to 80% of perimenopausal women are affected by hot flashes and night sweats.⁽²⁾ The menopause transition is also associated with mood changes, sleep disturbances, vaginal dryness, and painful sex, among other symptoms. These changes are the result of declining levels of estrogen, progesterone, and testosterone, as well as fluctuations in androgen levels that occur during this time.

Changes in the Body During Pregnancy

Pregnancy occurs in three stages: the first trimester, second trimester, and third trimester. Pregnancy progression is marked from the first day of a woman’s last period to birth, spanning an average of 40 weeks.⁽³⁾ 

Hormonal changes begin during the first trimester, when a fertilized egg is implanted in the uterine wall. During this stage of fetal gestation, essential organs, external structures, and sex organs develop. In the second trimester, muscle and bone formation progresses along with the development of eyebrows, eyelashes, and taste buds, continuing until the fetus comes to full term in the third trimester.⁽³⁾

While hormone levels may fluctuate throughout both perimenopause and pregnancy, the menopause transition is largely characterized by decreases in hormone levels. In contrast, hormones such as estrogen, progesterone, cortisol, and oxytocin typically increase during pregnancy.⁽⁴⁾

Perimenopause vs. Pregnancy Symptoms

Since both perimenopause and pregnancy involve many of the same hormones, women may experience similar symptoms, making it hard to distinguish between the two. Some symptoms that perimenopause and pregnancy often share include the following:

1. Irregular Periods: A woman’s menstrual cycle lasts an average of 28 days. While a missed period is usually the first symptom of pregnancy, some women may experience irregular periods, making early pregnancy sometimes difficult to detect.⁽⁵⁾ During the menopause transition, the length of the menstrual cycle can also change, along with changes in flow, longer or shorter periods, or missed periods.⁽⁶⁾

2. Hot Flashes: A hot flash is a sudden rush of warmth and sweating in the upper body, particularly the neck, face, and chest. Weakness, faintness, or heart palpitations may also occur.⁽⁷⁾ One study published in Fertility and Sterility found that out of more than 400 women, 35% experienced hot flashes while pregnant.⁽⁸⁾ Hot flashes are also one of the most frequently reported symptoms during perimenopause.⁽²⁾

3. Brain Fog: Hormonal fluctuations during pregnancy and perimenopause may affect cognition, particularly memory. However, these effects are typically mild and usually do not significantly interfere with daily functioning.^(9)(10)

4. Changes in Mood: Women who are pregnant or in perimenopause are at a higher risk for anxiety and depression.^(2)(11) Abrupt changes in mood are common during the first trimester of pregnancy.⁽³⁾

5. Fatigue: In a study of 300 women, researchers found that over 46% of perimenopausal women experienced physical and mental fatigue, while approximately 19% of premenopausal women reported similar symptoms.⁽¹²⁾ It’s also common for women to experience fatigue during the first trimester of pregnancy.⁽³⁾

6. Sleep Difficulty: Hot flashes, night sweats, and mental health symptoms can make falling and staying asleep difficult for perimenopausal women.⁽²⁾ Women in their third trimester of pregnancy may also have difficulty sleeping.⁽³⁾

7. Changes in Sex Drive: Decreased libido is common during the menopause transition, and changes in sex drive may also occur during pregnancy. While sexuality is unique to each person, some research shows that sexual desire among pregnant women and their partners tends to be low during the first trimester, increases during the second trimester, and decreases again throughout the third trimester.⁽¹³⁾

8. Headaches: Many women experience headaches during the first trimester of pregnancy.⁽³⁾ Similarly, perimenopause has been associated with more frequent headaches among women who experience migraines.⁽¹⁴⁾

9. Food Cravings: As hormone levels increase during pregnancy and decline during perimenopause, women may develop certain cravings or food aversions. Research indicates that pregnant women in the U.S. often gravitate toward foods that are high in sugar, like ice cream, chocolate, or fruit.⁽¹⁵⁾ On the other hand, a study in China found that women in perimenopause preferred vegetables and fruit over fast food or salty food.⁽¹⁶⁾

Although it can be difficult to differentiate between the signs of perimenopause and the early stages of pregnancy, there are some symptoms that tend to be more strongly associated with one over the other. There are also additional symptoms to take into account. Women who suspect they may be pregnant should see a doctor for an accurate diagnosis. The following are signs that a woman may be pregnant: 

1. Nausea or Vomiting: Nausea and vomiting, also known as morning sickness, are more closely associated with pregnancy than perimenopause. Some women may feel queasy or throw up during the first trimester.⁽³⁾

2. Tender Breasts: While some women may experience breast tenderness as menstruation becomes more irregular during perimenopause, sore breasts are a common symptom of pregnancy during the first trimester. Some women may also develop protruding nipples.^(3)(17)

3. Heartburn or GERD: It’s estimated that anywhere between 30% and 80% of pregnant women experience heartburn, a burning sensation in the chest due to the backflow of stomach acid into the esophagus. A study involving over 500 pregnant women found that reports of gastroesophageal reflux disease (GERD) symptoms (heartburn and regurgitation) increased throughout pregnancy, from 26% of women in the first trimester to 51% in the third trimester. Only about 9% of nonpregnant women reported symptoms.⁽¹⁸⁾

4. Bladder Symptoms: Pregnant women urinate more frequently due to hormonal shifts and the increased pressure placed on the bladder as the fetus grows. While hormonal changes during the menopause transition may also affect urination, one study showed that bladder symptoms were more common among women in the late reproductive stage compared to women in perimenopause. Therefore, increased urinary frequency is more closely associated with pregnancy.^(3)(19)

5. Missed Periods: Missed periods can occur both during pregnancy and perimenopause. However, the complete absence of a period is more common in pregnancy, while irregular periods are more closely linked to perimenopause. 

The Connection Between Pregnancy and Perimenopause Hot Flashes

Hormone fluctuations during pregnancy and perimenopause are believed to disrupt the regulation of body temperature, causing hot flashes.⁽⁸⁾ 

While more research is needed, hot flashes associated with pregnancy and those experienced in perimenopause are not thought to be different from one another.⁽⁸⁾ In fact, some research suggests a link between the age of a woman’s last pregnancy and the likelihood of experiencing hot flashes during perimenopause. Although results have varied, a study published in the Journal of Women’s Health involving 388 perimenopausal women found that women who reported their age at the time of their last pregnancy as 36 or older were at a lower risk for hot flashes than women who were last pregnant at the age of 35 or younger.⁽²⁰⁾

As women age, it can be difficult to determine whether certain physiological changes are indicative of pregnancy, perimenopause, a health condition, or aging. While at-home pregnancy tests can be purchased over-the-counter (OTC), the most reliable way for women to know whether they’re pregnant is to see a healthcare provider. A doctor can assess symptoms, conduct a pelvic exam, and issue a blood or urine test to confirm pregnancy. 

If perimenopause is the cause of symptoms, bioidentical hormone replacement therapy (HRT) may be recommended. Bioidentical hormones come from plants, and their chemical structure closely resembles that of natural hormones made in the body. HRT treatments can help reduce common symptoms during the menopause transition, including hot flashes, fatigue, mood changes, and decreased libido.