Arterial Blood Gases. Test Overview. An arterial blood gas (ABG) test measures the acidity (pH) and the levels of oxygen and carbon dioxide in the blood from an artery. This test is used to check how well your lungs are able to move oxygen into the blood and remove carbon dioxide from the blood.
How Often the Test Is Done During Your Pregnancy. Your doctor may use the Doppler often to listen to your baby's heartbeat during routine checkups, starting at about 8 to 10 weeks. Handheld Dopplers will not work quite this early.
They need to hear the heart beat to make sure you are healthy. If you have an irregular heart beat that means something is wrong. They also use a stethoscope to listen to your breathing (like if you have labored breathing or wheezing) and to listen to your stomach and organs move and pump.