I have a client that is nursing her nine month old infant.  The
     mother's periods had resumed, but they have now stopped.  The obvious
     answer would be a pregnancy, however, the baby has started to nurse
     again every 2 hours during the night - would this increase in nursing
     cause a delay in her periods when the baby is now 9 months old?  We
     thought that this might be the reason but we are looking for more
     scientific data, to agree or dispute with our theory.  She has no
     other signs or symptoms of pregnancy.