Why it's done

A nonstress test is used to evaluate a baby's health before birth. The goal of a nonstress test is to provide useful information about your baby's oxygen supply by checking his or her heart rate and how it responds to your baby's movement. The test might indicate the need for further monitoring, testing or delivery.

Normally, a baby's heart beats faster when he or she is active later in pregnancy. However, conditions such as fetal hypoxia — when the baby doesn't get enough oxygen — can disrupt this response.

Your health care provider might recommend a nonstress test if you have:

• A multiple pregnancy with certain complications
• An underlying medical condition, such as type 1 diabetes, heart disease or high blood pressure during pregnancy
• A pregnancy that has extended two weeks past your due date (post-term pregnancy)
• A history of complications in a previous pregnancy
• A baby who has decreased fetal movements or possible fetal growth problems
• Rh (rhesus) sensitization — a potentially serious condition that can occur, typically during a second or subsequent pregnancy, when your red cell antigen blood group is Rh negative and your baby's blood group is Rh positive.
• Low amniotic fluid (oligohydramnios)

Your health care provider might recommend having nonstress tests once or twice a week — and occasionally daily — depending on your health and your baby's health.