Some labs are relatively common, but not routinely done on all women. There is more information about each one of these in the following pages.
If your doctor or midwife suspect a problem with your blood pressure, s/he may want to do some lab tests to look for other signs. “PIH” stands for pregnancy-induced-hypertension. Both PIH and toxemia/pre-eclampsia have some common attributes. Both may involve complications with your kidneys. Toxemia/pre-eclampsia may also involve complications of the liver and blood clotting factors. “PIH labs” may help diagnose a problem or be used to establish a “baseline” for comparison later in the pregnancy.
Some of the tests commonly used to look for signs of a hypertensive disorder include the BUN, serum creatinine, platelet count, hematocrit, SGOT and uric acid (Glossary). Each of the values of these tests may be elevated in hypertensive disorders of pregnancy except the platelets, which may decrease.
Hemoglobin A1c is a specific type of hemoglobin produced in elevated amounts when a person’s blood sugar is too high. Hemoglobin is the molecule inside red blood cells which transports oxygen to the cells of the body. Since red blood cells have a fairly predictable lifetime (about 120 days), the amount of specific types of hemoglobin, such as A1c, gives a glimpse of the recent past. Elevated A1c may be an indication that a person has had elevated blood sugars in the recent past, and thus has implications for management of diabetic problems during pregnancy.
The infection, commonly known as “herpes”, is caused by the Herpes Simplex Virus (HSV). Genital herpes infection in adults is common. Herpes infection of the newborn is quite uncommon. If a woman becomes infected with HSV prior to a pregnancy, the risk of infection to a fetus or newborn is quite low. Most of the worst newborn herpes infection occur in women who develop their first herpes infection (a “primary outbreak”) during pregnancy and give birth to an infected premature baby.
The use of viral cultures to detect herpes and prevent newborn infection is somewhat limited. If your doctor or midwife suspect a primary outbreak, cultures may be helpful in making the diagnosis, and guiding the next step of the process (determining the risk to the fetus). However, in a person with a known history of herpes, cultures are usually not very helpful. Most people with recurrent herpes infections have symptoms (usually heralding the outbreak of herpes sores). Depending on the timing and location of herpes sores, a doctor or midwife may or may not recommend delivery by c-section if the sores are present during labor. (see Herpes Infection).
Varicella (Chicken Pox)
By early adulthood, most people have been exposed to, and are immune to the varicella virus. The Varicella Zoster Virus is one of the herpes viruses and causes both chicken pox and shingles. Chicken pox in the adult, and especially in pregnancy, can cause significant illness.
Most people develop lifelong immunity to chicken pox after they are exposed as children. Antibodies against the varicella virus can be detected in the blood. If one has the antibodies, s/he is considered immune to chicken pox. If a person does not have the antibodies, s/he is considered susceptible to the disease. A pregnant woman without antibodies should avoid anyone (usually children) suspected of having chicken pox.
Antibodies for Parvovirus B19, Toxoplasmosis, and Cytomegalovirus
When the body becomes infected with harmful organisms (whether the organism is a bacteria, virus or protozoan), the immune system produces antibodies. Antibodies are complex proteins which attack and disable the intruders. It is possible to draw a person’s blood and measure the specific type and quantity of the antibody when infection is suspected.
Early in an infection, the body produces immune globulin M (IgM). Later in the recovery phase of infection, the body produces immune globulin G (IgG). In many diseases, IgG protects against future infection and may be a sign of immunity.
Parvovirus B19 and Cytomegalovirus are both viruses capable of severe, debilitating infections in fetuses and newborns. Toxoplasmosis is a protozoan (a large single, celled organism) also known to cause newborn infections. Your doctor or midwife can use antibody tests to evaluate your risk for these uncommon infections if you have symptoms or think you have been exposed. (See Parvovirus B19 Infection, Toxoplasmosis Infection, or Cytomegalovirus Infection).
Autoimmune diseases are illnesses which occur when the body’s immune system produces antibodies against itself (called autoantibodies). Some of the autoimmune disease processes (for example, systemic lupus erythematosus, or SLE) are important in pregnancy, since they are associated with increased risks of miscarriage, stillbirth and maternal complications.
A host of autoantibody tests may be helpful in determining if a woman is at risk for poor pregnancy outcome. The most common is the ANA (anti-nuclear antibody). If a woman is producing this antibody, a second round of tests may look for other autoantibodies including the lupus inhibitor, anticardiolipin and other antiphoslipid antibodies.