Urine Tests During Pregnancy

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A urine test, or urinalysis, is an important part of routine prenatal care. During most prenatal visits, women will be asked to collect clean, midstream urine (also called “clean-catch urine specimen”) in a plastic cup (1). This means that a woman should clean her genital area with a sterile wipe before urinating, release urine into the toilet, and collect urine in a sterile cup. The urine sample is then screened by a healthcare provider for specific molecules involved in various body functions. Screening for these molecules allows pregnancy-related problems to be identified early, so that treatment and monitoring can be provided, and complications can be minimized.

What are some routine urine tests performed during pregnancy?

 Sugar. Urine tests are performed to evaluate levels of glucose (sugar) to identify women with gestational diabetes. Normal urine contains little or no glucose during pregnancy. However, high blood sugar levels result in increased levels of sugar in the urine. Gestational diabetes can develop if pregnancy hormones interfere with insulin and its ability to process glucose. Even if urine tests are normal, all women receive a glucose challenge test during weeks 24 to 28 of pregnancy (2). This glucose screening test involves consuming a high-sugar drink that contains 50 grams of glucose quickly, usually within 5 minutes, followed by blood collection after one hour. The blood is screened for glucose. As many as 5% of pregnant women may develop gestational diabetes, making it a common problem, so routine urinalysis and glucose blood screening midway through pregnancy are important prenatal tests.

Protein. Urinalysis is performed routinely to detect protein, or proteinuria, which may indicate a urinary tract or kidney infection or chronic kidney disease (3). If protein is found in the urine after week 20 of pregnancy, suspicion of preeclampsia may emerge, especially when coupled with high blood pressure. This is a serious condition affecting an estimated 7% of pregnancies and requires immediate treatment and monitoring. If preeclampsia is a concern, a woman may be asked to collect her urine over a 24-hour timeframe, so samples can be examined for the amount of protein. The amount of protein relative to creatinine, which is always in urine, can be measured to help make the diagnosis.

Bacteria. Urine tests can detect signs of urinary tract infections even if a woman has no physical symptoms. Urine tests may be performed to measure specific enzymes or products secreted by bacteria. Red or white blood cells in urine can also signal a urinary tract infection. If urine tests are suspicious for bacteria, a diagnostic urinary culture may be ordered to confirm if bacteria grow from a urine sample (4). Untreated urinary tract infections can cause serious complications during pregnancy, including pyelonephritis, a type of kidney infection. Urine tests that identify bacterial infections early are important, so that antibiotic treatment can be initiated before serious problems develop.

Ketones. Ketones are acids produced when fats are broken down for energy. If there are a lot of ketones in urine, this may be due to ketoacidosis related to diabetes. This is a serious condition that could lead to loss of consciousness, brain swelling, and organ failure. As with many urine tests, a colorimetric strip is placed into a urine sample to measure ketones. The strip will change color to indicate the level of ketones in the urine. Measuring ketones in urine samples can help avoid dangerous conditions for a mother and her baby.

Routine urinalysis is essential for optimal prenatal healthcare. Most women will go through their pregnancy receiving normal urine test results, which can be extremely reassuring. If a woman receives an abnormal urine test result, identifying these problems early allows treatment and monitoring, potentially avoiding serious complications during pregnancy.

References

Rita Nahta
Dr. Rita Nahta has a Ph.D. in pathology from Duke University. She lives in Atlanta, GA, where she serves as a medical school professor, teaching a variety of classes, including about the effects of drugs on pregnancy. She writes about women’s health, oncology, and medical education.

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