My 11-1/2-year-old daughter recently started menstruating for the first time. It lasted about four days and the flow seemed to be normal. However, she started again within about 18 days from the last day of her first period. Is that normal?
Yes, that sounds perfectly normal for someone going through puberty. Young girls are beginning puberty earlier than previously believed and are having their first period somewhat earlier as well. As puberty continues, most girls have their first menstrual period two years after the onset of breast development. Even after they have their first period, girls continue to grow taller and "regular" menstrual cycles usually do not happen for one to two years. During these first two years, one half to three quarters of cycles early on are anovulatory (no egg is released from the ovary), which accounts for this variability. Reassuring your daughter that what she is experiencing is normal should help during this sensitive time for teenagers.
The glands in the body and the hormones that communicate between the glands need to be functioning together to then have "regular" menstrual cycling. Remember that a menstrual cycle is defined as the number of days between the first day of bleeding with the last menses and the first day of bleeding with the next menses. The normal menstrual cycle lasts between 21 and 35 days. Changing cycle lengths from month-to-month can be normal. Most women usually bleed for three to seven days. If her bleeding seems excessive, too frequent, lasts more than a week, or if she has other associated symptoms, I would contact her physician.