Pregnancy Chances After Trigger Shot: A 12-13 Day Test

The probability of pregnancy when taking a pregnancy test on the 12th or 13th day after ovulation can vary based on several factors, including the timing of ovulation, the sensitivity of the pregnancy test, and individual hormonal levels. Generally, testing around this time can provide a reliable indication of pregnancy, as it is close to the expected date of menstruation. However

Hello Dr.
Tsao,
I had my menstrual period on July 16, and I only tested positive for ovulation on August 8 (I usually have a regular ovulation day, with a cycle length of 32 days).
I saw a doctor on August 9, and the ultrasound confirmed that I ovulated late this month.
I then received an ovulation trigger injection and started taking progesterone on August 11 (there was no embryo transfer, just the injection and progesterone).
As of yesterday, August 20, my period still hasn't arrived (although I understand that late ovulation can lead to a delayed period).
However, I wanted to take a pregnancy test, and I got faint second lines on two consecutive days (August 20 and 21) after the ovulation trigger injection, with the second line appearing after about 20 to 30 minutes.

Could you please advise whether the faint lines on the test are more likely due to residual medication from the ovulation trigger injection, or is there a higher probability that I am actually pregnant? Thank you for your response!

Pan, 20~29 year old female. Ask Date: 2022/08/21

Dr. Cao Guotao reply Obstetrics and Gynecology

Hello, you may be pregnant.
Wishing you good health.

Reply Date: 2022/08/21

More Info

When considering the chances of pregnancy after administering a trigger shot (often referred to as an ovulation trigger), it's essential to understand how these shots work and the timing of ovulation in relation to conception. In your case, you received a trigger shot after a confirmed late ovulation, and you began taking progesterone shortly thereafter.
The trigger shot, typically containing human chorionic gonadotropin (hCG), is designed to induce ovulation. It is usually administered when a follicle is mature, and ovulation is expected to occur within 36-48 hours. After receiving the shot, if ovulation occurs as expected, the egg can be fertilized by sperm if intercourse occurs within a suitable timeframe.

You mentioned that you tested for pregnancy 12-13 days after the trigger shot and observed faint lines on the pregnancy test. This timing is critical because it falls within the window where hCG levels would begin to rise if implantation has occurred. Generally, it takes about 6-12 days after ovulation for a fertilized egg to implant in the uterine lining, and then hCG levels start to increase, which can be detected by home pregnancy tests.

The faint lines you observed could indicate a few possibilities:
1. Pregnancy: If implantation occurred and hCG is being produced, you could be pregnant. The faintness of the line may suggest that the hCG levels are still relatively low, which is common in early pregnancy.

2. Residual hCG from the Trigger Shot: Since the trigger shot contains hCG, it can remain in your system for a short period. However, this typically clears from the body within 7-10 days after administration. Given that you tested 12-13 days post-trigger, it is less likely that the faint lines are solely due to the residual hCG from the shot, especially if you have not experienced any bleeding or other signs of menstruation.

3. False Positive: While less common, it is possible to receive a false positive result, particularly if the test is sensitive to lower levels of hCG.
Given your situation, if the faint lines persist or darken over the next few days, it would be advisable to follow up with a quantitative blood test for hCG. This test can provide a more definitive answer regarding your pregnancy status, as it measures the exact amount of hCG in your bloodstream.
In summary, while there is a possibility that the faint lines are due to residual hCG from the trigger shot, the timing of your test suggests that pregnancy is also a strong possibility. Monitoring your symptoms and following up with a healthcare provider for further testing will provide clarity. If you have any concerns or experience unusual symptoms, do not hesitate to reach out to your healthcare provider for personalized advice and support.

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