Third-trimester exams and tests

Routine exams and tests

At each prenatal visit, you can expect to be weighed and have your urine and blood pressure checked. Your health professional will monitor your fetus's growth and position by measuring the size of your uterus (fundal height) and feeling (palpating) your abdomen.

If your fetus is not in the head-down (vertex) position after 36 weeks (as confirmed by fetal ultrasound), your health professional may try to turn it gently from the outside (version). Version carries some risks, and not all health professionals are skilled in this technique. For more information, see the topic Breech Position and Breech Birth.

Late in your pregnancy, your health professional:

• Is likely to check you for group B streptococcus, which can cause severe newborn illness, disability, or death. This is done by rubbing the vaginal and rectal areas with a cotton swab. If you test positive for group B strep (or if for some reason you are not tested), you will be treated with antibiotics during labor.
• Will check to see how far the baby's head has dropped into your pelvis. Close to delivery, you may be checked to see whether your cervix has begun to stretch and open (cervical effacement and dilatation).
• May check you for hepatitis B. If you test positive for hepatitis B infection, your baby will receive the hepatitis vaccine and hepatitis B immune globulin (HBIG) within 12 hours of birth.

Additional testing

Later in pregnancy, your health professional may recommend an amniocentesis if:

• You are going to deliver prematurely. An amniocentesis is commonly used to see whether the fetus's lungs are developed enough for delivery.
• There is a concern about infection in the amniotic fluid.