When a girl receives her first period (menarche), the flow is usually heavy for the first few days and lighter towards the end. The first period can last for two days or for maximum of seven days, and in certain cases, there is no bleeding but only blood spots. The first few periods can be red, brown or pink in colour and can even be clumpy at times. The first period is usually different from the rest of the menstrual cycle and the flow keeps getting denser with time.
It takes about two years for the period cycle to get stabilised after girls get their first period. Menses in the starting are irregular because the reproductive hormones take time in getting balanced inside the body and keep fluctuating during different menstrual cycles. During the beginning of menstruation, the hormones are not stable and which is why ovulation does not occur during each cycle. The process of ovulation occurs in 2 per 10 cycles which leads to irregular periods. Accordingly, the menstrual cycle is expected to get stabilized by the sixth year because the ovulation happens in 9 out of 10 cycles and the periods tend to become regular.
The first few menstrual cycles can range between 21-45 days and can become shorter or longer — depending upon the hormones in the body. An average period cycle ranges in between 24-38 and girls start experiencing normal period cycles by the third year.