Irregular Periods and Early Pregnancy Testing Results

Irregular menstrual cycle + pregnancy test?

Hello doctor, my last menstrual period was on September 3rd, and my cycles have been irregular with unpredictable timing.
I started having unprotected intercourse in early October, but my period did not come.
I have been taking pregnancy tests almost every week, and until October 26th, I only saw one line.
On October 29th, I tested again and saw a faint second line.
That day, I went to the hospital for an abdominal ultrasound, but nothing was visible.
The doctor suggested a urine test to confirm the faint second line, stating that it was too early to see anything and advised me to return the following week.
Two days later, I went to another clinic for an ultrasound, and it was still faint.
The doctor mentioned that the embryo should be less than 20 days old, so I was told to come back for another scan.
When I returned a week later, the gestational sac measured 1.1 cm.
Due to my irregular cycles, we couldn't determine the exact date of conception and could only estimate based on size, which suggested about five weeks.
However, during my last visit, the doctor said it was less than 20 days, and now it suddenly appears to be five weeks? How many weeks pregnant am I actually? A pregnancy test can detect pregnancy 14 days after intercourse, and there were only three days between my tests on October 26th and 29th.

Q, 20~29 year old female. Ask Date: 2016/11/09

Dr. Cao Guotao reply Obstetrics and Gynecology

Hello, a typical pregnancy test is done at 4 weeks, while an ultrasound to check for the gestational sac is usually performed at 5 weeks.
The conception date can only be estimated roughly and cannot be calculated precisely.
Wishing you good health!

Reply Date: 2016/11/09

More Info

Understanding irregular periods and early pregnancy testing can be quite complex, especially when the menstrual cycle is not regular. Based on your situation, it seems you have been experiencing irregular menstrual cycles, with your last period starting on September 3rd. After having unprotected intercourse in early October, you noted that your period did not arrive, prompting you to take pregnancy tests weekly.
Initially, you received negative results until October 26, when you observed a faint second line on the test. This indicates the presence of the hormone hCG (human chorionic gonadotropin), which is produced during pregnancy. However, the faintness of the line can suggest that the hormone levels are still low, which is common in early pregnancy.
When you visited the hospital on October 29, the ultrasound did not show a visible embryo, which can happen if the pregnancy is very early. The doctor confirmed the presence of hCG in your urine but mentioned that the embryo was likely too small to be detected at that stage. This is a typical scenario in early pregnancy, as it can take time for the embryo to develop to a point where it is visible on an ultrasound.

The discrepancy in gestational age can be attributed to several factors. Typically, gestational age is calculated from the first day of your last menstrual period (LMP), which in your case would be September 3. However, since your cycles are irregular, it can be challenging to pinpoint the exact date of conception. The doctor’s estimate of "under 20 days" likely refers to the time since conception, while the ultrasound measurement of 1.1 cm suggests that the embryo is approximately five weeks old based on its size.
In early pregnancy, it is common for the gestational age to be estimated based on ultrasound measurements rather than the LMP, especially if the menstrual cycles are irregular. The embryo's size can provide a more accurate indication of its development stage.
Regarding the timing of pregnancy tests, it is generally recommended to wait at least 14 days after potential conception for the most accurate results. Since you tested on October 26 and received a positive result, it aligns with the expected time frame for detecting pregnancy. The faint line you saw could indicate that you were indeed pregnant, but the levels of hCG were still rising, which is why the line was not very dark.

In conclusion, based on your irregular cycles and the timeline of your tests and ultrasounds, it is likely that you are around five weeks pregnant, as indicated by the ultrasound measurement. It is essential to follow up with your healthcare provider for further monitoring and to confirm the pregnancy's progression. Regular check-ups will help ensure that both you and the developing embryo are healthy. If you have any concerns about your symptoms or the pregnancy, do not hesitate to reach out to your healthcare provider for personalized advice and support.

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