A pregnancy test can provide an accurate result up to ten days after intercourse. If the test is done early, its accuracy is reduced. The standard time frame is 10 to 14 days following sexual intercourse. HCG is produced two weeks following conception or ovulation; therefore, a false result may be given if the test is done too early.
In some cases, even 10 to 14 days following intercourse is still too early for testing. This is because your body may take longer for implantation after conception and ovulation. Since sperm can survive in the human body for up to five days, it is possible for a woman to conceive several days after having sex. Thus, if you received a negative result one week later, you should do the test again. This increases your chance of getting an accurate result.
After a missed period, the pregnancy test can be taken anytime. It is best if you take the test as soon as you miss your period or if you suspect pregnancy. There are some pregnancy tests which claim to give results before the missed period; however, these tests are more likely to be inaccurate. Some even claim to give the results as early as ten days after sex, but these tests may give a false positive or a false negative result.
In cases of women who do not get a regular period, it is best to perform the tests weeks after intercourse.
Menstruation and Conception
Human chorionic gonadotropin (HCG) is the pregnancy hormone. A woman’s cycle starts the first day of the menstrual period. The menstrual period commonly lasts for 3-7 days. As soon as the period ends, the hormones begin working to prepare the egg for ovulation. Generally, ovulation is on day 14 of the cycle. During this time, the ovaries release ovum. If the ovum is unfertilized, it remains for about 5-8 days in the female genital tract.
Sperm may take around two days to reach the fertilization site and unite with the ovum. The site where fertilization takes place is the ampulla. If the ovum becomes fertilized, it may take 6-7 days to reach the uterus. This means that implantation occurs around 8 days after unprotected sex occurs. As the implantation progresses, the placenta develops.
HCG is secreted by the placenta. In the ovary, a structure called corpus luteum is kept active by the HCG. In order to maintain the inner lining of the uterus and pregnancy, the corpus luteum secretes the hormone progesterone. If implantation does not occur, the corpus luteum regresses, since there is no HCG to maintain it. The level of progesterone drops and the inner lining of the uterus from the uterine wall begins to separate. Around day 28, the menstrual cycle repeats.
If you are pregnant, a test will generally give a positive result 8 days after the unprotected sex occurred. There are certain brands that claim their pregnancy tests will determine whether a woman is pregnant four days before the missed period; however, the success rate of these tests is only 69 percent. If it detects 3 days before, then its success rate is 83 percent. Two days before increases to 93 percent.
False Negative Test
If a pregnancy test is performed on the first day of your missed menses, it may provide a false negative result. The common cause of this is early testing. Sometimes, even individuals with very high levels of pregnancy hormone can receive a false negative result. If the test result comes back as a false negative, another test can be taken again the following week.
Another method of testing is to do a blood test, which is far more accurate than standard pregnancy tests.
Various Tests and Their Accuracy
Below is a list of the testing methods and their accuracy.
The success rate of a blood test is 99 percent. Even the smallest traces of pregnancy hormone can be detected by a blood test. The test taken should be a quantitative test.
Quantitative vs Qualitative Blood Tests
The amount of HCG in the blood is measured by the quantitative blood test. In the initial first four weeks of pregnancy, the HCG hormone is at its peak. After which its level starts tapering off. Using a quantitative blood test, the doctor can measure the amount of HCG and check whether the pregnancy is progressing normally or not. The qualitative test will only help determine if you are pregnant.
A blood test can be done earlier than a urine test. Urine tests can only provide accurate results either the first day after a missed period or two weeks after conception. Blood tests can determine if you are pregnant within 7-12 days after conception.
Blood tests can only be taken at a doctor’s clinic; thus, they are more expensive and not as convenient as home tests. Blood tests are also required to be sent to a lab for analysis, which means that the results will not be available instantly. It may take hours or possibly days before you receive your test results.
Urine Tests and Home Pregnancy Tests
The failure rate of a urine test or pregnancy test done at home is 6 percent. The accuracy of a home pregnancy test can be affected by the following factors:
- Early testing
- Fertility medication or any medications that affect the HCG levels
- Whether the urine cup is clean or dirty
- A presence of blood or protein in urine
- Faulty test kit
- Sensitivity of the test kit
- Ovarian tumor
- Recent miscarriage
Women who take fertility medication should consult their doctor about when to take the test.
Stick and Dip Method
Usually, the stick and dip method of testing for pregnancy is available over-the-counter. The sticks are dipped into urine. The minimum amount of pregnancy hormones needed to provide a result varies from brand to brand.
Ultrasound scanning can only detect pregnancy 3-5 weeks following intercourse. Initially, only a small sac is visible with the scan. Later, the heartbeat becomes visible.
Accuracy of Home Pregnancy Tests
If used correctly, home pregnancy tests can provide accurate results. The results are as accurate as the results of the urine test done in a doctor’s clinic. This test detects the hormone HCG, which the body makes only during pregnancy. These tests are only accurate when taken after the missed period. However, If the kit has expired or was used incorrectly, it will not give correct results. Always check the expiration date on the package and read instructions carefully before taking the test.
What If the Early Pregnancy Test Is Negative?
If you suspect that you are pregnant, even after receiving a negative result, test again three days after the first test. Some women at the time of a missed period may have low levels of HCG. It can be as low as 1 to 10.
If you continue to receive a negative result, but still feel that you may be pregnant, go in for a blood test to receive the most accurate results.
Pregnancy Test After Irregular Period
Women with irregular periods have a tougher time detecting pregnancy. For such cases, you cannot go by the monthly cycle to determine if you are pregnant. If you have irregular periods, the best way to determine if you should take a test is to look out for the early symptoms of pregnancy. If you experience the following symptoms 2-3 weeks after having unprotected sex, use a home pregnancy test to determine if you are pregnant or not.
Can You Get a False Positive on a Pregnancy Test?
Although some have argued that it is impossible to get a false positive on a test, it does actually happen. In present day, pregnancy tests are highly sensitive. Shortly after implantation occurs, chemical pregnancy can be picked up by these tests. In the past, these chemical pregnancies would be undetected because they were lost before the actual test could be performed.
However, the probability of getting a false positive result is very low. If you get a positive result, it is always a good idea to do another test at home or confirm it with the help of a blood test.
Pregnancy Test Availability
Any local pharmacy, grocery store, or drug store will have testing kits available for purchase. These are less expensive. At certain health care centers, they are available free of charge. You can also get one from your nurse or doctor.