Fetal Lung Maturity Test

What is a fetal lung maturity test?

A fetal lung maturity test checks the development of an unborn baby's lungs to see if the baby will have breathing problems after birth (respiratory distress syndrome). Your health care provider takes fluid from inside the amniotic sac for this test with a procedure called amniocentesis. The amniotic sac is a thin sac filled with fluid that surrounds the baby in the uterus. The sample of amniotic fluid is tested in the lab.

When is it used?

This test may be done when early delivery of the baby may be likely or necessary. Your health care provider can use the result of the test to help weigh the risks of early delivery against the possible risks of waiting until the baby is more mature. Results of the test can be used to help prevent respiratory distress syndrome.

How do I prepare for this procedure?

It helps to have a full bladder, so you may need to drink a lot of water before the procedure. Follow any other instructions your health care provider gives you.

What happens during the procedure?

The baby's heart rate is checked before and after the procedure. Your abdomen is cleaned with an antiseptic. Usually your skin is numbed with an anesthetic. Ultrasound helps the technologist guide the needle through your abdomen and uterus, away from the baby and to the area where the most amniotic fluid is. You may feel some discomfort when the needle is inserted into your abdomen.

A small amount of fluid is withdrawn and sent to the lab. The fluid is tested in various ways. The test results help the health care provider predict whether the baby's lungs are developed enough for delivery.

What happens after the procedure?

Depending on the reason for the test, you may be kept in the hospital or you may be discharged after the procedure. The health care provider will ask you to rest for 24 hours.

What are the benefits of this procedure?

The test helps your health care provider see how mature the baby's lungs are. If the lungs are not fully developed, the baby could have serious problems breathing after birth and might need extra oxygen or might die. When possible, your provider may decide not to deliver the baby until the lungs are more mature. If the baby needs to be delivered soon, the baby may be given a medicine 12 to 24 hours before delivery to help the lungs mature more quickly. The medicine is given as a shot to the mother.

What are the risks associated with this procedure?

The overall risk of complications from this procedure is very low. Less than 1% of women have problems. However, you should know what problems can occur. The following are possible complications of amniocentesis:

• excessive loss of blood
• infection
• harm to the baby, placenta, or cord from the needle
• premature breaking (rupture) of the amniotic sac
• premature contractions or labor.

When should I call my health care provider?

Call your right away if:

• You start having contractions or severe cramping. (It is normal to have some brief cramping.)
• You have bloody or persistent liquid vaginal discharge. (It is normal to have a little spotting or leaking.)
• You develop a fever over 100°F (37.8°C).
• You notice a decrease in fetal movement.

Call during office hours if:

• You have questions about the procedure or its result.
• You want to make another appointment.