Pregnancy Test Accuracy: What to Do When Your Period is Late

Accuracy of Pregnancy Tests

The last menstrual period was from June 28 to July 2.
On July 16, there was sexual intercourse with condom use throughout, but it was not checked for any leaks.
The period was expected on July 31, but it has not arrived.
On the mornings of August 3 and 4, pregnancy tests were taken, both showing one line.
The following day, a visit to the hospital for a urine test and a transvaginal ultrasound was conducted.
The ultrasound doctor mentioned that the endometrium was thickened, but it was unclear whether this indicated an upcoming period or pregnancy.
Later, a visit to the outpatient doctor confirmed that the urine test result indicated no pregnancy.

Is it true that there is no pregnancy? On August 5, a medication to induce menstruation was administered, but two days later, the period has still not arrived.
I am unsure if this is due to stress or if the pregnancy test results were inaccurate.
Thank you.

199.27, 20~29 year old female. Ask Date: 2016/08/07

Dr. Cao Guotao reply Obstetrics and Gynecology

Hello, after taking general menstrual induction medication, menstruation typically occurs within 3 to 7 days.
You may observe for now; however, if menstruation does not occur after one week, it is advisable to consult a gynecologist.
Wishing you good health.

Reply Date: 2016/08/07

More Info

When it comes to understanding pregnancy test accuracy, especially in the context of a missed period, there are several important factors to consider. Based on your description, you had your last menstrual period from June 28 to July 2, and you had unprotected intercourse on July 16. Your expected period was due on July 31, but it did not arrive. You conducted home pregnancy tests on August 3 and 4, which returned negative results, and subsequent urine tests and a vaginal ultrasound at the hospital also indicated no pregnancy.

Timing of Pregnancy Tests
The timing of when to take a pregnancy test is crucial for accuracy. Most home pregnancy tests are designed to detect the hormone human chorionic gonadotropin (hCG), which is produced shortly after a fertilized egg attaches to the uterine lining. The levels of hCG can typically be detected in urine about one week after a missed period. Since your period was due on July 31, testing on August 3 and 4 was appropriate, but it may still be early for some tests to detect pregnancy, especially if implantation occurred later than expected.

Factors Affecting Test Results
1. Test Sensitivity: Different pregnancy tests have varying sensitivities. Some can detect lower levels of hCG than others. If you used a less sensitive test, it might not have detected pregnancy even if you were pregnant.

2. Timing of Ovulation: If your menstrual cycle is irregular or if you ovulated later than usual, this could affect the timing of when hCG levels rise enough to be detected.
3. Stress and Hormonal Factors: Stress can impact your menstrual cycle and may delay your period. Hormonal imbalances or other health issues could also play a role in missed periods.

Ultrasound Findings
The ultrasound indicated that your endometrium (the lining of the uterus) was thickened. A thickened endometrium can occur in both early pregnancy and in preparation for menstruation. This finding alone does not confirm pregnancy, especially if hCG levels are low or undetectable.

Follow-Up Actions
Given that you received a negative urine pregnancy test and the ultrasound did not confirm pregnancy, it is reasonable to conclude that you are not pregnant at this time. However, if your period does not arrive after receiving the injection to induce menstruation, it is advisable to follow up with your healthcare provider. They may recommend further testing or evaluation to determine the cause of your missed period.

Conclusion
In summary, while your home pregnancy tests and medical evaluations suggest that you are not pregnant, it is essential to monitor your cycle closely. If your period does not resume after the injection or if you continue to have concerns, further investigation may be warranted. Always consult with your healthcare provider for personalized advice and to address any ongoing concerns regarding your menstrual cycle and reproductive health.

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