Tamoxifen is a drug that is used to treat breast cancer. According to the National Institutes of Health, tamoxifen halts the effects of estrogen on the breasts. During pregnancy, however, estrogen production increases. Tamoxifen use should be avoided during pregnancy. In fact, according to the National Cancer Institute, tamoxifen can actually harm a developing fetus. Because of this, it is vitally important to watch for signs of pregnancy while on tamoxifen.
Fatigue
Some of the earliest signs of pregnancy can be similar to the common side effects of tamoxifen. These include fatigue, nausea, cramping and a missed period. One of the earliest pregnancy symptoms is often severe and otherwise unexplainable fatigue. Not all women taking tamoxifen experience fatigue, so if you are taking the drug and suddenly notice this symptom, consult your doctor, as it could be a sign of pregnancy.
Nausea
Nausea is another common side effect women may experience when taking tamoxifen. Of course, it is also another common early symptom of pregnancy. Unexplained nausea that develops suddenly after you have been taking the drug should be assessed by your doctor. If you could potentially be pregnant, it is probably a good idea to take a pregnancy test for safety's sake.
Menstrual Irregularities
According to the National Cancer Institute, another common side effect of tamoxifen use in women is an irregular menstrual cycle. In other words, you may have a late period, or no period at all while taking the drug. Despite this, a missed period should be taken seriously, especially if there is a chance you could be pregnant. If your period has not started two weeks after you usually ovulate, you could potentially be pregnant.
Cramps
Cramps are another common side effect of tamoxifen that can mimic early pregnancy. Tamoxifen cramps are often located in the stomach, according to the National Institutes of Health. However, during early pregnancy it may be hard to distinguish between stomach cramps and uterine cramps. Uterine cramps often occur around the time a fertilized egg implants in the uterine wall, which is also around the time most women expect their period to begin. If you notice unusual cramps, and have not started your period, you might be pregnant.
Breast Tenderness
Some other common early pregnancy symptoms differ from the usual tamoxifen side effects. If you experience any of these pregnancy symptoms while on tamoxifen, you should consult your doctor immediately. One of these is breast tenderness. Breast tenderness is often one of the earliest signs of pregnancy, and can appear as early as two weeks after an egg is fertilized.
Food Cravings or Aversions
Another common early symptom of pregnancy, food aversions can appear early in the first trimester. While nausea and decreased appetite can be side effects of taking tamoxifen, sudden food cravings and aversions are unique to pregnancy. If you notice these symptoms of pregnancy while taking tamoxifen, consult your physician immediately.
Basal Body Temperature
Another symptom unique to early pregnancy is an elevated basal body temperature (BBT). Your BBT is your temperature at rest. It spikes during ovulation, and does not dip again until your period begins. If your BBT is elevated for longer than two weeks, chances are you are pregnant. It is important to watch for this or any other signs of pregnancy while on tamoxifen. If you notice any new symptoms, or if a few symptoms occur together, it might be time to take that pregnancy test.
