Pregnancy tests are based on the principle of detecting the presence of pregnancy hormone known as human chorionic gonadotropin in the urine or blood because this hormone will be present only in the urine or blood of a pregnant woman.
Usually hCG is released, when a fertilized egg gets implanted to the wall of the uterus and the implantation may happen any time after the sixth day of conception and in about 10 percent of the women, implantation happens a day after the missed period. There are two kinds of pregnancy tests and they are blood test and urine test.
Blood test can be done only with the doctor’s prescription, but urine test can be done either at the clinic or at home using a pregnancy test kit. A quantitative blood test evaluates the accurate quantum of hCG present in the blood and its result are highly accurate and hence is more reliable. As the blood test can detect even the minute amount of hCG in the blood, it can be done from six to eight days after ovulation with good accuracy.
Home Pregnancy Tests
Home pregnancy test can be done easily at home and is inexpensive as well. Most of the drugstores provide home pregnancy test kit over the counter. Women should collect their early morning urine and with the help of a dropper, add a few drops of the urine so collected to a special apparatus in the home pregnancy test kit and the result can be read instantaneously.
Certain kit manufactures recommend for a repeat test to confirm pregnancy after a few days. However the accuracy of urine tests depends on how the test is conducted.
Factors That Influence The Accuracy of Home Pregnancy Tests
Expiry Date and Instructions on the Kits
Before conducting any pregnancy test, make sure that the kit has not crossed its expiry date. Also follow the instructions given on the kit strictly while carrying out the pregnancy test; else you may end up with inaccurate result. Recheck the result after a gap of five to ten minutes for more accurate result.
Sensitivity of Pregnancy Test
Usually the concentration of hCG in urine is counted as milliInternational Units (mIU). Hence, pregnancy test kits with a sensitivity of 20 to 25 mIU are more accurate over the pregnancy test kits with sensitivity of 50 to 100 mIU, in the early days of pregnancy.
The first urine in the morning should be the ideal sample for carrying out the pregnancy test. This is because, the morning urine should have good concentration of hCG than the more diluted urine obtained during the rest of the day.
Time to Conduct the Pregnancy Test
The level of hCG in urine will be very low during the first day after a missed period and it will be difficult for most of the pregnancy test kits to detect them properly or the results often appears very faint. Hence, a pregnancy test conducted a day after missed period have only 97% accuracy. Hence the best time to carry out a pregnancy test is one week after the missed period. Once the pregnancy is confirmed, visit a gynecologist who would advise you on the precautions to be followed to ensure a smooth pregnancy.