Why would a 13 year old period came 1 month and then did not return next month?

There are several reasons why a 13-year-old girl's period may have come once and then not returned the following month. Some possible causes include:

1. Normal variation in menstrual cycles: It is common for menstrual cycles to be irregular during the first few years after a girl's first period. This is because the hormones that regulate the menstrual cycle are still developing and fluctuating. As a result, some cycles may be longer or shorter than average, and some months a girl may not ovulate at all, which can lead to missed periods.

2. Stress: Stress can affect the menstrual cycle, causing periods to become irregular or even stop temporarily. This is because stress can disrupt the balance of hormones in the body, which can interfere with the normal functioning of the menstrual cycle.

3. Illness: Some illnesses, such as thyroid problems or diabetes, can affect the menstrual cycle. If your daughter has any underlying health conditions, it is important to see a doctor to rule out any medical causes for her missed period.

4. Pregnancy: Although it is less likely in a 13-year-old girl, it is possible for her to become pregnant even if she has only had one period. If your daughter is sexually active, it is important to consider the possibility of pregnancy and to take a pregnancy test if she misses a period.

5. Birth control: If your daughter is taking birth control pills, it is possible that she may experience irregular periods, missed periods, or changes in her menstrual cycle. This is because birth control pills work by altering the levels of hormones in the body, which can affect the menstrual cycle.

If you are concerned about your daughter's missed period, it is important to talk to her doctor. They can help to determine the cause of the missed period and recommend any necessary treatment or follow-up.