Pregnancy Tests: Accuracy and Timing Concerns

Pregnancy test (not using first morning urine)

Hello Doctor: I had sexual intercourse on March 28 (my boyfriend wore a condom throughout and only withdrew after ejaculation, but he remained inside for a few seconds after ejaculation).
I took a pregnancy test on April 10 and April 18.
The test on April 10 at the obstetrics and gynecology clinic was negative, and the doctor said I was not pregnant.
On April 18, I used a home pregnancy test, which also showed negative (one line).
My questions are: 1.
Would the fact that I did not use first morning urine for both tests on April 10 and April 18 affect the results? 2.
If I took a pregnancy test at the obstetrics and gynecology clinic 13 days after intercourse (urine test and not first morning urine), would the result be accurate? 3.
On April 18, I urinated about half an hour to an hour before the pregnancy test; would this affect the HCG concentration and thus the result? 4.
Based on the above, is my chance of being pregnant high? 5.
My expected period was due on April 7, but as of today (April 20), I still have not gotten my period.
Could this indicate a possible pregnancy? Thank you, Doctor, for taking the time to answer my questions.
I wish you success in your career and all the best.

Niming, 20~29 year old female. Ask Date: 2019/04/21

Dr. Huang Jianzhong reply Obstetrics and Gynecology

On March 28, I had sexual intercourse (my boyfriend wore a condom throughout and only withdrew after ejaculation, but he remained inside for a few seconds after ejaculation).
I took a pregnancy test on April 10 and April 18.
The test on April 10 at the gynecologist's office was negative, and the doctor said I was not pregnant.
On April 18, I used a home pregnancy test, which also showed negative (one line).
My questions are:
1.
Would the fact that I did not use first morning urine for the tests on April 10 and April 18 affect the results?
Answer: No, it will not affect the results.

2.
If a pregnancy test is taken 13 days after intercourse at the gynecologist's office (urine test and not first morning urine), will the result be accurate?
Answer: Yes, it will be accurate.

3.
I urinated approximately half an hour to an hour before the pregnancy test on April 18.
Would this affect the HCG concentration and the result?
Answer: No, it will not affect the result.

4.
Based on the above, is my chance of pregnancy high?
Answer: The chance of pregnancy is low.

5.
My expected menstrual period was on April 7, but as of today (April 20), I still have not gotten my period.
Could this possibly indicate pregnancy?
Answer: Take another pregnancy test on April 25.

Reply Date: 2019/04/21

More Info

Understanding pregnancy tests can be quite complex, especially when considering factors such as timing, urine concentration, and the accuracy of the tests themselves. Based on your situation, let’s break down your questions and concerns regarding the possibility of pregnancy.

1. Impact of Testing Timing: The timing of when you take a pregnancy test is crucial. Home pregnancy tests (HPTs) are designed to detect the hormone human chorionic gonadotropin (hCG), which is produced shortly after a fertilized egg attaches to the uterine lining. Generally, the best time to take a pregnancy test is after a missed period, as this allows for the hCG levels to rise sufficiently for detection. Since your expected period was on April 7 and you tested on April 10 and April 18, you were within a reasonable timeframe to detect pregnancy if it had occurred.

2. Accuracy of Non-Morning Urine Tests: While morning urine is typically more concentrated and may yield more accurate results, testing at other times of the day can still be reliable, especially if you have not consumed large amounts of fluids prior to testing. However, the sensitivity of the test can be affected by dilution. If you tested on April 10 and April 18 with non-morning urine, the results could still be valid, but there is a slight chance that the hCG levels were not high enough to detect if you were indeed pregnant.

3. Effect of Recent Urination on Results: If you urinated about half an hour to an hour before taking the test on April 18, it is possible that the hCG concentration in your urine was lower than it would have been if you had not urinated recently. This could potentially lead to a false negative result, especially if you were in the early stages of pregnancy.

4. Likelihood of Pregnancy: Given that you had two negative tests and considering the timing of your sexual activity, the likelihood of pregnancy appears low. However, it is important to note that no test is 100% accurate, and false negatives can occur, particularly if the test is taken too early or if urine dilution affects the hCG concentration.

5. Missed Period and Pregnancy Possibility: Since your period was due on April 7 and you have not yet menstruated as of April 20, this could indicate a potential pregnancy, especially in light of the negative tests. Stress, hormonal imbalances, or other factors can also cause a missed period. If you continue to miss your period, it may be advisable to consult with a healthcare provider for further evaluation, which may include a blood test for hCG, as blood tests are more sensitive and can detect pregnancy earlier than urine tests.

In summary, while your negative pregnancy tests suggest that you are not pregnant, the missed period and the timing of your tests warrant further investigation. If you remain concerned about the possibility of pregnancy or if your period does not arrive soon, I recommend consulting with a healthcare provider for a more definitive assessment. They may suggest a blood test or an ultrasound to clarify your situation. Remember, it’s always best to seek professional advice when in doubt about your reproductive health.

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