A pregnancy test attempts to determine whether a woman is pregnant. Markers that indicate pregnancy are found in urine and blood, and pregnancy tests require sampling one of these substances. One such marker is human chorionic gonadotropin (hCG), that is produced by the trophoblast cells of the fertilised ova (eggs). While hCG is a reliable marker of pregnancy, it cannot be detected until after implantation; this results in false negatives if the test is performed during the very early stages of pregnancy. Most chemical tests for pregnancy look for the presence of the beta subunit of hCG, or human chorionic gonadotropin, in the blood or urine. hCG can be detected in urine or blood after implantation, which occurs six to twelve days after fertilization. False negative readings can occur when testing is done too early. Quantitative blood tests and the most sensitive urine tests usually begin to detect hCG shortly after implantation, which can occur anywhere from 8 to 10 days after ovulation.
Ovulation, in some women, may not occur at a predictable time in the menstrual cycle, however. A number of factors may cause an unexpectedly early or late ovulation. This holds true especially for women with a history of irregular menstrual cycles.
Sometimes the Urine Pregnancy Test kits take some time to detect the HCG in urine. Thus it is advisable to repeat the test at serial intervals more than once to confirm or negate pregnancy.
If still in doubt, or you have missed your period, please consult a doctor who will determine what else can be done to address your concerns about a possible pregnancy.
These Q&A’s are for educational purposes and should not be relied upon as a substitute for medical advice you may receive from your physician. If you have a medical emergency, please call 911. These answers do not constitute or initiate a patient/doctor relationship.