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.
Question: How early can a doctor hear the babyâs heartbeat? Answer: Before the age of radar and sonar as applied medically, it was the olâ stethoscope that was used most often to listen to the baby. Unfortunately this meant an audience of one â the one who sat between the earpieces of the stethoscope.