Complete Blood Count (CBC): What This Common Blood Test Measures and Why Your Doctor Ordered It

The complete blood count, or CBC, is a routine blood test that measures the different cells in your blood, including red blood cells, white blood cells, and platelets. It gives your care team a broad picture of your overall health and helps detect a wide range of conditions, from infections and anemia to bleeding or clotting disorders.

The 3-hydroxypropionate test measures the amount of a substance called 3-hydroxypropionate (also written as 3-OH-C3) in the amniotic fluid. Amniotic fluid is the clear, slightly yellowish liquid that surrounds and protects a developing baby in the womb. This test is a specialized prenatal test performed in a chemistry laboratory.

Your doctor may order this test as part of a routine checkup, to investigate symptoms such as fatigue, weakness, fever, easy bruising, or unexplained weight loss, or to monitor an ongoing condition or treatment. The CBC can confirm an infection, show signs of anemia or blood loss, and track how therapies like chemotherapy affect your blood cells over time.

This test is performed during pregnancy to check for certain inherited metabolic disorders. These are genetic conditions that affect how the body converts food into energy. Elevated levels of 3-hydroxypropionate in the amniotic fluid may indicate conditions such as multiple carboxylase deficiency, biotinidase deficiency, or other metabolic disorders that involve problems with how the body processes certain proteins and fats.

A sample is collected by drawing blood from a vein, usually on the inside of your elbow or the back of your hand. A phlebotomist cleans the site, wraps a band around your upper arm, inserts a small needle, and fills a collection tube. The process takes only a few minutes, and you may feel a brief pinch. Pressure and a bandage are applied afterward.

The sample is collected through a procedure called amniocentesis. During this procedure, a thin needle is inserted through the mother's abdomen into the uterus to withdraw a small amount of amniotic fluid. The procedure is performed under ultrasound guidance to ensure safety. The fluid sample is then sent to a laboratory for analysis.

Results are compared with reference ranges for each cell type. A high white blood cell count may point to infection or inflammation, while low values can suggest anemia, blood loss, or certain chronic conditions. Abnormal platelet levels may affect clotting. Your doctor will interpret the numbers together with your symptoms and history, since many factors can influence a single value.

Normal levels of 3-hydroxypropionate in amniotic fluid indicate a lower likelihood of the tested metabolic disorders. Elevated levels suggest that the unborn baby may have a metabolic disorder. However, your healthcare provider will interpret the results in conjunction with other tests and your family history to make an accurate diagnosis.