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.
Your doctor listens to your heart with the aid of a stethoscope. The opening and closing of your valves make sounds (lub dub) known as the heart sounds. The doctor can evaluate your heart and valve function and hear your heart's rate and rhythm by listening to your heart sounds.