You may qualify to file as head of household even though you do not claim an exemption for your child if you meet all of the following requirements:
  1. You are unmarried or considered unmarried on the last day of the year.
  2. You paid more than half of the cost of maintaining a household that is your home and the main home of your child for more than one-half of the year.
  3. Your child is your qualifying child for purposes other than the dependency exemption and the child tax credit. [ยง2(b)(1)]
2013 IRS Pub 501, pages 8-10 has more details on head of household filing status.