How Prenatal Testing Works

Swab Tests

At different times during pregnancy, your doctor may take swab samples (Q-tip) from your vagina or rectum. The cells on the swab will be examined under a microscope or cultured to determine various conditions or diseases.

In the first trimester, you may have a Pap smear in which cells from your cervix are examined to look for signs of cervical cancer. Later, when you are closer to delivery (around week 35), your doctor will take swabs from your vagina and rectum. These swabs will be cultured to look for Group B streptococcus bacteria. These bacteria are common in many women and are considered a normal part of an adult woman's reproductive system. For an unborn child, however, these bacteria can spread during delivery and cause several problems:

  • respiratory distress - problems with breathing that threaten the baby's life
  • mental retardation
  • vision problems
  • hearing loss

Group B strep infections can be treated with IV antibiotics before delivery.