Third Trimester: Urine Screen for Glucose and/or Protein
At each prenatal visit through the first, second, and third trimesters, the expectant mother may be asked to give a urine specimen, which will usually be tested in the office using a dipstick to screen for the presence of glucose (sugar) and/or protein. Although small amounts of both glucose and protein are normally present in urine, high levels can indicate a problem and may call for further testing.
A high level of protein in the urine is a warning sign. It may indicate kidney damage or disease or it may be a transient elevation due to, for example, an infection, medication, or emotional or physical stress. Examples of additional tests that may be done to help determine the cause include a 24-hour urine protein test, full urinalysis, or urine culture (to identify any bacteria or yeast present; see Bacteriuria).
Of particular concern during the second and third trimesters is preeclampsia (sometimes called toxemia or pregnancy-induced hypertension), a disorder characterized by high blood pressure and large amounts of protein in the urine that occurs in approximately 8% of all pregnancies. Symptoms include swelling, sudden weight gain, headache, and vision changes. Risk factors include first pregnancy; being pregnant with more than one child; age (teenagers and women over 40 years of age); being African American; and having pre-existing diabetes, hypertension, or kidney disease. It can result in a decrease of air and food getting to the baby through the placenta, causing low birth weight or other complications. If caught early enough, however, through routine checking of blood pressure and urine protein levels, health problems for the mother and baby due to preeclampsia can be prevented.
High urine glucose levels may be a sign of undiagnosed diabetes that is already present in the mother or gestational diabetes, a form of diabetes that can develop during pregnancy. A positive urine test for glucose will usually be followed by a confirmatory blood glucose test, which is also routinely used to screen for gestational diabetes during the second trimester (between 24 and 28 weeks of pregnancy).