Pregnant women should be tested for diseases that directly affect their health and thus secondarily affect the outcome of the pregnancy. Some of these tests are mandated by law or public health regulation. Others are widely accepted as the standard of care. Failing to diagnose or manage maternal illness properly is a major source of liability in obstetrics. The problem arises because most pregnant women are healthy. This makes it easy to attribute what would otherwise be symptomatic illness to the normal effects of pregnancy.

Once the tests are done, the physician must be very careful to evaluate the results in every patient and take action when necessary. In caring for a pregnant woman, a few days can make a tremendous difference in the outcome, so a physician should pay particular attention to the timely evaluation of test results. If a result has not been received, it should be treated as bad news until the result is available. If the syphilis serology or the blood type has been lost, it should be repeated promptly. The only true negative screening test is the one that has been reported by the laboratory and evaluated by the physician.

Tests should never be ordered simply as a defensive measure. It is legally more dangerous not to act on a test that indicates maternal illness than not to do the test. For example, if a patient has a negative rubella titer, her physician should be concerned if she develops a rash. What may be dismissed as an allergy in an immune patient should be worked up in a woman who may have rubella. In addition, this patient should be immunized as soon as she delivers. The obstetrician who failed to immunize a patient after her first pregnancy may be liable for a congenital rubella baby from her second pregnancy.