Pregnancy Test

A pregnancy test is a test used to indicate whether or not a woman is pregnant. Pregnancy tests can sample blood or urine to detect the presence of a certain type of hormone that designates a pregnancy. Urine tests that detect this hormone, called human chorionic gonadotropin (hCG), usually require a woman to wait at least ten days after missing a menstrual period before testing a urine sample. Blood tests can determine pregnancy slightly sooner, approximately six to eight days after fertilization, or the union of male and female reproductive cells. Home pregnancy tests allow a woman to test for hCG in her urine in her own home. These tests reveal the results through simple symbolic or language-based indicators.

History

Ancient peoples were known to test for pregnancy using various methods. The Egyptians would pour a woman's urine over wheat and barley seeds. If sprouts grew from the seeds, it meant the woman was pregnant. The type of grain that grew also determined the sex of the baby. If barley grew, the baby would be male; if wheat grew, the baby would be female. Methods changed by the Middle Ages. The common pregnancy test of this time was based on urine color. Pregnancy urine was supposedly a pale yellow color and had a cloud on its surface. Some people mixed wine with urine and observed its reaction to see whether or not a woman was pregnant. These methods were eventually abandoned over the centuries.

By the nineteenth century, the most accurate pregnancy detection methods involved a woman being observant of certain physical signs such as morning sickness. It was not until the end of the nineteenth century that scientists gained a better understanding of female hormones and their relation to pregnancy. This era coincided with the medical community's new emphasis on prenatal care. By the early twentieth century, scientists recognized that the hCG hormone was present only in pregnant women and could be used to test their blood and urine to determine pregnancy. Women were encouraged to visit the doctor to confirm pregnancy.

The first urine-based pregnancy test was developed in the 1960s, but the method was not always foolproof. Urine could be sent to laboratories to test for the presence of hormonal pregnancy markers. Home kits were soon developed that instructed women on how to collect a urine sample at home, which they could then physically transport to a lab or send the sample to a lab by mail. Scientists continued to improve upon the hCG tests over the years. In 1976, the Food and Drug Administration (FDA) granted approval for the first at-home pregnancy test, known as the Early Pregnancy Test (EPT). EPT became the first pregnancy test on the market in 1978. The test cost ten dollars and required a woman to test her own urine sample using premeasured ingredients such as purified water and red blood cells from sheep that reacted with the urine to detect hCG. The test took two hours to show results and was more accurate for positive results than negative results.

The twenty-first century saw further improvements in home pregnancy testing, simplifying the method and the design. Pregnancy tests were soon made available over the counter at drug stores. Modern tests involved urinating on a small plastic stick containing a chemical strip that reacted with the urine to indicate hCG. Modern tests made results available in minutes. The home pregnancy test became the most widely used test by women, though doctors often used blood tests to confirm the pregnancy.

Urine Tests

Home pregnancy tests are completed by placing a urine sample on a plastic stick that contains a prepared chemical strip. Women remove the pregnant test stick from its packaging and urinate on the absorbent area indicated in the instructions. Urine often is directly applied to the absorbent strip by placing the strip under streaming urine for a few seconds. With some tests, urine can be collected in a container and the strip can be dipped in the urine for several seconds. Once complete, the test takes one to two minutes to show results. Result time is dependent on the brand. Pregnancy indicators also vary by brand. Some tests show a simple plus or minus sign to indicate a positive or negative pregnancy. Others use the words "pregnant" or "not pregnant." Tests also can indicate results by using different colors to represent pregnancy or non-pregnancy. Home pregnancy test kits are more accurate when conducted by experienced technicians. Accuracy falls when consumers perform the tests themselves, usually because they misunderstand or incorrectly read instructions. Improper usage can lead to both false positives and false negatives.

Blood Tests

Although modern home pregnancy tests have a much higher level of accuracy at detecting a pregnancy than ever before, blood-based tests remain the most precise method for detecting early pregnancy. Blood tests can detect a pregnancy earlier than urine tests, but results take longer to process. These tests can be performed at a doctor's office, where the blood is then analyzed for the presence of hCG. Doctors often order blood tests to confirm a woman's pregnancy after she has already performed a pregnancy test at home.

Two types of blood pregnancy tests exist. The qualitative hCG test checks to see if hCG is present in the blood. These tests provide a simple "yes" or "no" answer to whether or not a woman is pregnant. A quantitative hCG test measures exactly how much hCG is in the blood. Quantitative tests measure the concentration of hCG, which also can be useful in detecting potential problems during pregnancy. Combined with other tests, hCG levels can rule out the possibility of an ectopic pregnancy, in which a fertilized egg implants outside of the uterus. Doctors often keep track of hCG levels in a woman who has suffered a miscarriage to ensure her health.

Bibliography

"E.P.T. Pregnancy Test: Key Information." EPT Family Planning Solutions. Prestige Brands Holdings, Inc. Web. 30 Jan. 2016. http://www.eptfamily.com/products/ept%E2%84%A2-pregnancy-test

"Home Pregnancy Tests: Can You Trust the Results?" Mayo Clinic. Mayo Foundation for Medical Education and Research. Web. 30 Jan. 2016. http://www.mayoclinic.org/healthy-lifestyle/getting-pregnant/in-depth/home-pregnancy-tests/art-20047940

"Pregnancy Test." Planned Parenthood. Planned Parenthood Federation of America Inc. Web. 30 Jan. 2016. https://www.plannedparenthood.org/learn/pregnancy/pregnancy-test

"Pregnancy Test." MedlinePlus. U.S. National Library of Medicine. Web. 30 Jan. 2016. https://www.nlm.nih.gov/medlineplus/ency/article/003432.htm

"Pregnancy Tests." WebMD. WebMD, LLC. Web. 30 Jan. 2016. http://www.webmd.com/baby/guide/pregnancy-tests

"A Timeline of Pregnancy Testing." Office of NIH History. National Institutes of Health. Web. 30 Jan. 2016. https://history.nih.gov/exhibits/thinblueline/timeline.html