Blood work during pregnancy: the tests and how to read them

Why pregnancy needs its own guide

Blood work during pregnancy has two jobs. Some tests look for conditions that can be treated before they affect you or the baby, such as anemia, an infection or a blood group mismatch. Others, like the glucose test in the second trimester, are screenings for problems that pregnancy itself can create.

The prenatal blood tests page walks through the whole schedule, from the first visit to the third trimester, and explains which lines on your lab report move simply because you are pregnant. Hemoglobin and platelets drift down, and creatinine falls as the kidneys filter more, so a value printed against a non-pregnant range can be flagged for no good reason.

The test most people worry about

The glucose test is the one that fills forums. In the United States it usually comes in two steps: a sweet drink with a blood draw one hour later, then, if that number is high, a longer fasting test. The gestational diabetes test results page explains the cutoffs, why many people who fail the first step turn out fine, and what happens next.

Where the rest of the site helps

Pregnancy does not change how a report is laid out. The guides on reading a complete blood count, iron tests and what an out-of-range value means still apply, as long as you keep in mind that pregnancy shifts several of the numbers they discuss.