<div class="row-fluid">  <div class="span6">    <p>On an average a period lasts between 3 to 5 days. It is normal for a girl to have irregular periods in the beginning. During this time, the duration of her periods may vary from as short as 2 days to as long as 7 days. It can take up to a year for periods to become regular.</p>  </div>  <div class="span6">	  <img width="380" height="317" alt="Illustration of a girl looking inside her skirt to find if her periods have arrived, to her side are four panels showing the amount of blood flow in first four days of menstruation - Menstrupedia" src="/assets/quickguide/physiology/physiology-menstruation-last.jpg"/>  </div></div><div class="source">  <h5>References:</h5>  <ol>  <li>Menstruation and the menstrual cycle fact sheet, <a rel="nofollow" class="reference" href="http://womenshealth.gov/publications/our-publications/fact-sheet/menstruation.cfm" target="_blank">http://womenshealth.gov</a></li>  <li>Menstrual cycle: What's normal, what's not, <a rel="nofollow" class="reference" href="http://www.mayoclinic.com/health/menstrual-cycle/MY01541" target="_blank">http://www.mayoclinic.com</a></li>  </ol></div>

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