When undergoing fertility treatments like intrauterine insemination (IUI) or in vitro fertilization (IVF), timing is everything. Knowing when to take ovulation trigger shots, when to time intercourse or insemination, and when to take a pregnancy test can optimize your chances of success. Here’s a look at how many days after a trigger shot you should test for pregnancy.
What is a Trigger Shot?
A trigger shot contains hormones that help control ovulation timing. The most commonly used trigger shot is called human chorionic gonadotropin (hCG). This mimics the hormone that a growing placenta normally produces. Taking a trigger shot leads to ovulation between 24-36 hours later for most women.
Doctors prescribe trigger shots for timed intercourse, IUI, or IVF cycles. For IUI and IVF, the goal is to coordinate egg retrieval right around the time of ovulation. For timed intercourse, the aim is to pinpoint optimal days to have sex to conceive. In all cases, the trigger shot gets the ovaries ready to ovulate one or more mature eggs.
When to Take a Pregnancy Test After IUI
With IUI, sperm is placed directly into the uterus right around the time of ovulation. This increases the number of sperm that can reach the eggs, improving chances of fertilization. IUI is often combined with medications to stimulate ovulation and trigger shot timing.
If you have undergone IUI, doctors typically recommend waiting:
- 10-14 days after the IUI procedure to take a home pregnancy test
- 14-16 days after the IUI to get a beta hCG blood test
The trigger shot contains hCG, so a pregnancy test could show up as positive before you’re actually pregnant. Waiting 10-14 days allows enough time for the trigger to leave your system. A blood test 14-16 days after the IUI can detect very low levels of hCG if implantation has occurred.
Why the Waiting Period?
There are a few reasons to wait before testing after an IUI:
- Avoid false positive from trigger shot – Because the trigger shot contains hCG, testing too soon may give a falsely positive pregnancy test. Waiting 10-14 days allows the trigger to leave your body.
- Allow time for implantation – It takes about a week after fertilization for an embryo to implant and start producing hCG. So testing too early could miss an early pregnancy.
- Detect lower levels of hCG – A blood test can pick up very low levels of hCG a few days before a home urine test turns positive.
The two week wait after IUI can feel long. But try to hold off on early testing to avoid disappointment from false negatives or positives. Follow your clinic’s recommendations on when to take a pregnancy test after the trigger shot.
When to Test After IVF
IVF involves retrieving eggs, fertilizing them in a lab to create embryos, and transferring the embryo(s) into the uterus. Timing of the egg retrieval is precisely controlled with fertility medications and trigger shots.
After the embryo transfer, your clinic will let you know the best time to take a pregnancy test. This is typically:
- 9-12 days after a day 5 embryo transfer
- 11-14 days after a day 3 embryo transfer
This corresponds to about two weeks after egg retrieval, when the embryo would be implanting and starting to produce hCG. As with IUI, it’s important to avoid extremely early testing.
Why Wait to Test After IVF?
Here’s why your clinic will advise waiting 9-14 days after embryo transfer before testing:
- Allow the hCG trigger shot to leave your body – Testing too soon could result in a false positive from the lingering trigger shot.
- Give the embryo time to implant and produce hCG – hCG isn’t detectable immediately after implantation. Waiting 9-14 days allows levels to rise.
- Prevent false negatives – Testing too early could result in a false negative, since hCG may not be high enough to detect yet.
While it’s hard to remain patient during the two week wait after IVF, hold out until the advised testing timeframe. This will give you the most accurate results.
Urine vs. Blood Pregnancy Tests
After embryo transfer or IUI, you have the option of taking a home urine pregnancy or coming into the clinic for a blood test. Which is better?
A quantitative beta hCG blood test can detect lower levels of hCG compared to a qualitative urine test. Blood tests are more precise, detecting hCG levels as low as 1 to 2 mIU/mL. Home urine pregnancy tests usually don’t turn positive until hCG levels reach 25-50 mIU/mL.
So if given the option, a blood test offers the earliest, most sensitive results. It may turn positive a few days before a home test. However, urine tests are easier and cheaper to use at home.
How Many Days After Ovulation to Test?
If you’re trying to conceive through timed intercourse without medical intervention, you may not take a trigger shot. But you can still time when to take a pregnancy test based on your ovulation date.
Here’s a look at when you can expect a positive test based on when you ovulated:
| Days Past Ovulation | Pregnancy Test Results |
|---|---|
| 7 DPO | Too early, wait a few more days |
| 8 DPO | May be too early still, test again in 2-3 days |
| 9 DPO | Some positive results, but could be too early for many |
| 10 DPO | Around 50% of pregnancies can be detected |
| 11 DPO | 80% of pregnancies can be detected |
| 12 DPO | More than 90% of pregnancies can be detected |
| 13-14 DPO | 97% of pregnancies can be detected |
As you can see, the most reliable results come when you wait until at least 10-12 DPO. Even then, a negative test doesn’t rule out pregnancy, since implantation could have occurred later. If your period doesn’t arrive within a week of testing, retest.
How Long After Implantation to Test?
Embryo implantation happens about 8-10 days after ovulation. That’s when the fertilized egg attaches to the uterine lining and starts producing hCG. HCG doubles every 48 hours in early pregnancy.
If you know exactly when implantation happened, here’s the timeline for pregnancy test accuracy:
- 1-2 days after implantation – too early, implantation just occurred
- 3-4 days after implantation – may be too early, but some positive results
- 5-7 days after implantation – very accurate, enough time for hCG to rise
The tricky part is that most women don’t know their exact implantation date. That’s why the most reliable way to test is to wait until about 10-12 DPO, or about a week to 10 days after ovulation.
How Long After Conception to Test?
Fertilization of the egg happens within the first 24 hours after ovulation. Then it takes another 7-10 days for the fertilized egg to travel down and successfully implant in the uterine lining.
Here’s when you can expect positive pregnancy test results after conception:
- 1 week after conception – too early to test, implantation not complete
- 2 weeks after conception – may be able to get a positive result
- 3 weeks after conception – highly accurate results if conception occurred
- 4 weeks after conception – definitive positive or negative result in nearly all cases
While it’s tempting to test as soon as a week after having unprotected sex, this will often give falsely negative results. Try to hold out for two weeks for the most accurate outcomes.
Reasons for False Negative Results
Keep in mind that even if you are pregnant, you may get a negative pregnancy test result, especially if testing too early after a trigger shot. Reasons include:
- Low hCG – There needs to be enough hCG in your system for the test to detect. Waiting longer after implantation allows hCG to increase.
- Diluted urine – Drinking extra fluids before testing can dilute the hCG in urine, causing a false negative.
- Expired test – Outdated tests may not accurately detect hCG.
- Improper testing – Not following the instructions can impact the results.
- Ectopic pregnancy – An ectopic pregnancy may not produce enough hCG for detection.
- Chemical pregnancy – Very early loss of a pregnancy before detection may cause hCG levels to drop.
If you strongly suspect pregnancy but are getting negative home tests, have your hCG levels checked by blood test. This is more likely to pick up lower concentrations of hCG compared to urine.
Tips for Accuracy
To maximize accuracy of at-home pregnancy tests:
- Read the instructions and follow them closely.
- Check the expiration date and avoid using expired tests.
- Try not to drink too much fluid right before testing.
- Test again a day or two later if still unsure of results.
- Use first morning urine, which may contain more hCG.
- Choose a test with a low hCG detection threshold of 10-20 mIU/mL.
Conclusion
When undergoing fertility treatments, timing is critical. While it’s hard to wait, hold off on early pregnancy testing until your doctor’s recommended timeframe after the trigger shot. This prevents falsely positive or negative results and allows enough time for implantation to occur.
If you’re trying to conceive without interventions, begin testing no earlier than 10 DPO for the most reliable outcomes. Knowing what to expect for hCG detection based on days past ovulation or embryo transfer helps set realistic expectations.
While challenging, try to be patient during the two week wait before testing. Follow the timing guidelines from your clinic. Schedule a blood test if still uncertain to detect even tiny amounts of hCG. With the right timing, you can get an accurate result and hopefully celebrate a positive pregnancy test!