“Just relax. Try not to think about it, because there’s nothing you can do now,” your friend advises you after your most recent intrauterine insemination (IUI).
Aren’t suggestions like that just… beyond frustrating? Your friend’s right, of course. But they’re also presuming that their advice can be followed — which is sometimes wrong.
In reality, for many people, relaxing after an IUI is so much easier said than done. You want to know — yesterday, preferably — if it worked.
But unfortunately, there are good reasons why you shouldn’t take a pregnancy test before your clinic advises you to. And in many cases, that’s at least 14 days after your IUI.
To understand why you can take a pregnancy test about 14 days after IUI, it’s important to understand how IUIs — and the treatments that typically accompany them — fit into the whole conception timeline.
Timed for ovulation
In an IUI, sperm are injected into the uterus directly. But as with sex, an IUI has to be timed accurately in order for pregnancy to occur.
It does no good for sperm to be hanging around in your reproductive organs unless there’s an egg that’s ready for them. The release of an egg is called ovulation, and in a healthy natural cycle, it typically happens a couple weeks before your period is due.
In a natural IUI — that is, one without fertility drugs — you’ll receive ultrasound monitoring and possibly be asked to take at-home ovulation tests to pinpoint your ovulation date. You’ll get the IUI a day or so before your expected ovulation window.
Did you know?
Most often — especially in cases of infertility but also for situations where same-sex couples or single individuals use sperm donors — fertility drugs and frequent ultrasound monitoring are used in the lead-up to IUI to pinpoint when a mature egg will be released from the ovaries.
This aligns with what happens in a natural cycle, except that the drugs can be used to change the timing a bit and can also lead to more than one egg maturing (and releasing). More than one egg = higher chances of pregnancy, but also higher chances of multiples.
The fertilized egg’s journey
If an IUI works, you end up with a fertilized egg that then needs to travel down one of the fallopian tubes to the uterus and implant. (This is the same as what would need to happen if fertilization happened as a result of sex.) This process — fertilization to implantation — can take about 6 to 12 days, with the average being around 9 to 10 days.
From implantation to adequate levels of hCG
You begin producing the pregnancy hormone hCG after implantation — and not before.
Home pregnancy tests work by picking up hCG in the urine. These tests have a threshold — meaning they can only detect hCG if your level is above that threshold. This is usually around 20 to 25 milli-International Units per milliliter (mIU/mL), though some more sensitive tests may pick up smaller amounts.
It will take a few days after successful implantation for you to have enough hCG in your urine to turn a home pregnancy test positive.
All this adds up to the need to wait 14 days after your IUI before taking a home pregnancy test. Your clinic may go ahead and schedule you for a blood hCG test 14 days post-IUI as well.
Doing the math
If it takes 6 to 12 days after a successful IUI for a fertilized egg to implant, and 2 to 3 days for hCG to build up, you can see why it’s best to wait at least 14 days to take a pregnancy test.
Sure, if the fertilized egg only takes 6 days in your case, you may be able to take a pregnancy test at 9 or 10 days post-IUI and get a faint positive. But you could also get a negative when, in fact, everything worked — and that can be discouraging. So for the most accurate results, wait.
Things get a little more complicated if your IUI includes certain medications, but the 14-day guideline still applies — and may be even more important.
The trigger shot
If your doctor wants to time your IUI even more precisely, they may prescribe a “trigger shot.” This injection of hormones tells your body to release its mature egg(s) in preparation for an IUI (rather than wait for it to happen naturally). Your doctor will usually schedule the IUI for 24 to 36 hours after the shot.
Here’s the kicker: The trigger shot usually contains hCG to the tune of 5,000 or 10,000 IUs. It’s literally what “triggers” your body to release any mature eggs. (What a multitasker!)
To see why that’s a problem, imagine taking a home pregnancy test a few hours after your trigger but before your IUI. Guess what? It would be positive. But you’re not pregnant — you haven’t even ovulated!
Depending on the dose, it can take about 14 days for the trigger shot to leave your system. So if you take a pregnancy test sooner than 14 days after your IUI and get a positive, it may be a false positive from the leftover hCG in your body — not from new hCG produced after implantation. And false positives can be devastating.
‘Testing out’ the trigger
Some women choose to “test out” their trigger. For this, they’ll purchase a bunch of cheap home pregnancy tests and take one daily, starting a day or two after their IUI.
The test will of course be positive initially, but should get lighter and lighter as the trigger shot leaves your system over the next two weeks. If you get a negative test but then start getting positives again — or if the line has become very faint and then starts getting darker in the days following — it may indicate newly produced hCG from an implanted embryo.
Your doctor may also have you start progesterone supplements right after your IUI. These are designed to thicken your uterine lining to make it more receptive to implantation. Progesterone can also help support pregnancy if your natural levels are low.
Unlike the trigger shot, progesterone won’t mess with a home pregnancy test. But progesterone can give you common pregnancy symptoms whether the IUI worked or not. (It’s probably increased levels of progesterone in pregnant women that causes telltale signs like morning sickness and sore boobs. So supplementing can do the same.)
Bottom line: Don’t rely too much on symptoms if progesterone is part of your IUI plan. Take a home pregnancy test 14 days after the IUI — or when your clinic advises you — and if it’s negative, you unfortunately may have to attribute your symptoms to the progesterone supplements you’re on.
While you’re waiting to test, you may start to have some really early signs of pregnancy — especially toward day 13 or 14. If you’re not on progesterone, these might be promising:
- sore boobs
- frequent urination
- implantation bleeding
But these symptoms don’t always occur, even in women who are pregnant. The only sure signs are a missed period with a positive pregnancy test from your doctor’s office.
The two week wait (TWW) after an IUI can be excruciatingly difficult, but it’s worth it to avoid potential false positives and false negatives on home pregnancy tests. Follow your clinic’s instructions and wait at least 14 days post-IUI before taking a test.
Many clinics will schedule you for a pregnancy blood test at the 14-day mark. A blood test can detect lower levels of hCG and is considered even more accurate than urine tests.
Hang in there. We see you, and we know how eager you are to see that positive. If you must take a test before your TWW is up, know that we totally understand. Just don’t put all your hope or despair in what you see, and test again when your doctor tells you to.