Taking a pregnancy test is an emotional time for many women. With so much riding on the result of the test, women would like to know about the accuracy of the result they receive. Unfortunately, this does not always occur and a negative pregnancy test does not always mean a woman is not pregnant. Women need to learn when they can trust a negative result on a pregnancy test and when they may need to retest.
Significance
Women who receive a negative result on a pregnancy test may be lulled into a false sense of security. They may engage in behavior that they wouldn't do if they believed there was a chance they may be pregnant, including smoking cigarettes, drinking alcohol, using illicit drugs or engaging in other unhealthy habits. Knowing the possibility of false-negative results on a pregnancy test may help these women behave cautiously and avoid risky behavior until they conclusively confirm the results.
Causes
Pregnancy tests work by detecting the presence of the pregnancy hormone human chorionic gonadotrophin, or hCG. This pregnancy hormone is only present after the embryo implants into the lining of the uterus, which usually occurs six days after ovulation or later, according to the National Women's Health Information Center. When a woman takes a pregnancy test before the embryo implants or before hCG levels have reached high enough to detect, she will receive a negative result on a pregnancy test even though she is pregnant. Using an expired test, not following the pregnancy test instructions or drinking too much fluid before taking the test may also cause false negative results, according to MayoClinic.com.
Prevention
Women should wait until they miss a period before taking a pregnancy test for the most accurate results. This gives the pregnancy hormone hCG enough time to build up to become easily detected by a pregnancy test, which makes the results of the test more accurate. Women who do not want to wait until after their period may consider getting a blood pregnancy test taken, as these typically prove more accurate than home pregnancy tests, explains the American Pregnancy Association.
Considerations
While some pregnancy tests can detect hCG at a concentration of 20 mlU, others cannot detect hCG until the concentration reaches as high as 50mlU, explains the American Pregnancy Association. Pregnant women prove less likely to experience a false-negative result with a test that is more sensitive, so they may want to consider checking the sensitivity level before purchasing a pregnancy test.
Warning
While false-negatives often occur due to late implantation or testing too early, having low levels of hCG levels in early pregnancy may indicate a problem with the pregnancy. Pregnant women who received a false-negative result around the time of their missed period should consider getting a quantitative blood pregnancy test, sometimes referred to as a beta hCG test. This test measures the exact amount of hCG, which can give a doctor a good idea if the pregnancy is developing normally.
