Understanding “DPO,” or Days Past Ovulation, is helpful when considering a home pregnancy test. This refers to the number of days that have passed since an egg was released from the ovary. Home pregnancy tests detect a specific hormone in urine to determine if pregnancy has occurred.
How Pregnancy Tests Work
Home pregnancy tests detect human chorionic gonadotropin (hCG), a hormone produced during pregnancy. After a fertilized egg implants in the uterine wall, the developing placenta begins to release hCG, which then enters the bloodstream and, subsequently, the urine.
Tests contain antibodies that react to hCG, leading to a visible positive result. The amount of hCG in the urine increases rapidly in early pregnancy. For a test to show a positive result, the hCG level must reach a certain “threshold” that the test is designed to detect.
When to Take a Pregnancy Test
Timing is important when taking a pregnancy test due to how hCG levels rise. Implantation, the process where the fertilized egg attaches to the uterine lining, typically occurs between 6 and 12 DPO, with 8 to 10 DPO being the most common timeframe. Once implantation happens, the body starts producing hCG, which then begins to increase.
HCG levels generally double approximately every 48 to 72 hours in early pregnancy. Testing too early, before sufficient hCG has accumulated, can result in a false negative, even if pregnancy has occurred. Waiting a few days after your expected period provides a higher chance of detecting adequate hCG levels.
Many highly sensitive pregnancy tests can detect hCG levels as low as 6.3 to 10 mIU/mL. While these tests might show a positive result earlier, testing closer to or after a missed period still yields more reliable results. Using first morning urine is often recommended because it is typically the most concentrated, containing the highest amount of hCG.
Understanding Your Test Results
A positive pregnancy test result, even a faint line, generally indicates pregnancy. If you receive a positive result, contact a healthcare provider for confirmation and to discuss next steps. They may recommend a blood test, which can detect even lower levels of hCG, or an ultrasound.
A negative test result does not always mean you are not pregnant. Factors like testing too early before hCG levels are high enough or using diluted urine can lead to a negative result despite pregnancy. If you test negative but your period does not start, or if you continue to experience pregnancy symptoms, retest in a few days.
Sometimes, an early positive test might be followed by a negative result or the start of a period; this indicates a chemical pregnancy. This is an early miscarriage that occurs shortly after implantation, before a gestational sac can be seen on an ultrasound. If you have concerns about your test results or your menstrual cycle, consulting a healthcare professional is always the best course of action.