Pregnancy begins when the sperm from the man fertilizes the egg cell released from the woman's ovaries. The period from this moment until the end of the 8th week is called the embryonic period, and from the 8th week until birth, it is referred to as the fetal period.
Once the embryo implants into the endometrium, the inner lining of the uterus (about 5-6 days after fertilization), the pregnancy hormone called human chorionic gonadotropin (HCG) is secreted by the cells surrounding the embryo. The main principle of pregnancy tests is to detect this pregnancy hormone.
As pregnancy progresses, the β-HCG hormone, which increases in the blood, begins to appear in the urine after surpassing a certain threshold, leading to a positive result in the urine pregnancy test. A blood pregnancy test also measures the amount of B-HCG in the blood and can detect the presence or absence of pregnancy even before a menstrual delay. Urine tests can never reach the reliability of blood tests. While the presence of pregnancy is unlikely to be falsely indicated in a urine test, if it shows the absence of pregnancy, considering the possibility of early pregnancy, the test should be repeated after some time. (In very early pregnancies, the urine test may not detect the pregnancy. This situation may also apply to the blood test with a very low probability.)
The BETA-HCG hormone measured in the blood is used to detect pregnancies that cannot be detected by urine tests or seen with ultrasound, as well as in the diagnosis and monitoring of conditions such as ectopic pregnancy, miscarriage, and molar pregnancy (also known as a hydatidiform mole). You can find detailed information about blood pregnancy tests and B-HCG hormone by clicking here.
When does the urine pregnancy test give results after intercourse?
The urine pregnancy test cannot give results in the days immediately after intercourse. Generally, it is necessary to wait until a menstrual delay for it to give accurate results.
The reason for this: The logic behind the urine pregnancy test is based on the HCG hormone, which is formed due to pregnancy, passing from the mother's blood to the urine and being detected in the urine. Pregnancy can occur in the days close to the ovulation period. Even if pregnancy occurs with intercourse close to the ovulation day, it takes 6-10 days for the pregnancy to progress to the uterus and settle there. After settling in the uterus, the HCG hormone secreted from the pregnancy can pass into the mother's blood. In fact, it may take a few more days for this hormone to pass from the mother's blood to her urine. Because of all these, in short, if pregnancy occurs after intercourse close to the ovulation period, it takes almost 15 days for the HCG hormone, which is secreted due to this pregnancy, to pass into the mother's urine. This corresponds to the next menstrual period, that is, the time when the pregnancy occurs and the delay in the period is expected to coincide.
Therefore, if there is suspicion of pregnancy after intercourse, the urine pregnancy test should be done after a menstrual delay. If no pregnancy is detected in the test, it should be repeated one week later to increase reliability. In this way, the reliability of the test, which is 90% in the first test, can increase to 95% if the second test is performed.
A positive test result (indicating pregnancy) is more reliable than a negative result (indicating no pregnancy). However, in any case of menstrual delay, it is important to consult a doctor because even if the test indicates pregnancy, it may not be a normal pregnancy; it could be an ectopic pregnancy. Even if the test indicates no pregnancy, you may be pregnant without realizing it.
Diagnosis of Pregnancy with Ultrasound:
When the period is delayed by a week, which means the pregnancy is 5 weeks old, the pregnancy sac can be seen with a vaginal ultrasound; for it to be seen with an abdominal ultrasound, the pregnancy needs to be at least 6 weeks old, which means a delay of 2 weeks in the period.
The pregnancy sac can be seen with a transvaginal ultrasound when the pregnancy test (BHCG) value reaches 1500. The pregnancy sac can be seen with an abdominal ultrasound when the BHCG value reaches 2000-3000; it cannot be seen earlier.
A positive pregnancy test is definite evidence of the presence of pregnancy in the body, but this pregnancy may not be a normal one; it could be inside or outside the uterus (ectopic pregnancy). Whether the pregnancy is inside the uterus can only be determined with ultrasound, not with urine or blood pregnancy tests.
Summary
Pregnancy tests are used to determine whether a woman is pregnant or not. These tests are based on detecting the pregnancy hormone HCG. Urine pregnancy test generally needs to be done after the menstrual delay in order to give accurate results.
Result of Urine Pregnancy Test
Urine pregnancy test cannot give results in the days immediately after intercourse; it should be done after waiting for a menstrual delay.
Even if pregnancy occurs due to intercourse close to the ovulation day, it may take 6-10 days for the pregnancy to settle in the uterus and for the HCG hormone to pass into the urine.
If there is suspicion of pregnancy after intercourse, the urine pregnancy test should be done after a menstrual delay. If no pregnancy is detected in the test, it should be repeated one week later.
Reliability of Pregnancy Test
A positive result of the test (indicating pregnancy) is more reliable than a negative result.
In case of any menstrual delay, it is important to consult a doctor regardless of the test result, as the pregnancy may not be a normal one.
Diagnosis of Pregnancy with Ultrasound
When the period is delayed by a week, the pregnancy sac can be seen with a vaginal ultrasound; for it to be seen with an abdominal ultrasound, the pregnancy needs to be at least 6 weeks.
When the pregnancy test (BHCG) value reaches 1500, the pregnancy sac can be seen with a transvaginal ultrasound. When the BHCG value reaches 2000-3000, the pregnancy sac can be seen with an abdominal ultrasound.
Result of the Pregnancy Test
A positive pregnancy test is definite evidence of pregnancy in the body, but this may not be a normal pregnancy.
Whether the pregnancy is inside the uterus or not can only be determined through ultrasound, not through urine or blood pregnancy tests.
In light of this information, it is important to follow the monitoring processes recommended by the doctor based on the results of the pregnancy test.
