Probably the number one question when trying to conceive aside from “When should we have intercourse?” is “When to test for pregnancy?”

The answer varies, depending on when you implanted, what brand of pregnancy test you have, etc.

Let’s look at what happens in the body first, to give you an idea of why it can take up to 10 days or longer to see a result.

First, when ovulation occurs the egg pops out of the ovary and into the fallopian tube. The egg will only live for 12 to 24 hours if it doesn’t get fertilized. This is why it’s important to have sperm in the fallopian tube waiting for the egg. Sperm can live up to five days in the fallopian tube. Once the egg, if fertilized within the first day, will sit in the fallopian tube for a couple of days, taking its time rolling along toward the opening into the uterus. It takes another day or so for the fertilized egg to float into the uterus and to find the spot where it will implant. Up until that moment, your body will not produce any hCG – the hormone that the pregnancy test picks up to show a positive.

When to test for pregnancy depends on how many days past ovulation you are. Implantation takes place anywhere from 3 to 10 days after ovulation. In about a day or so after implantation, the implanted fertilized egg sends signals to the corpus luteum – the cyst on the ovary that formed when the egg popped out – to begin producing hCG and more progesterone. It’s this hCG that is detected when using a home pregnancy test. At first, the levels will be low, starting at around 10, then doubling every other day. Depending on how much hCG is first emitted into the body will depend on when a home pregnancy test will show a positive result.

With the very sensitive home pregnancy tests, ones that detect 15 mIU/hCG you can test as early as 8 days post-ovulation, assuming that you implanted early. Normally, a test that detects 20 mIU/hCG can show a positive at 10 days post-ovulation. Tests that detect 40-50 mIU/hCG can show a positive at 12 days post-ovulation, and tests that detect 100 + mIU/hCG usually show positives at around 14 days post-ovulation. This is all under the assumption that implantation took place early. If implantation takes place later, around 10 days post-ovulation, and then even a sensitive test won’t show a positive until 12 to 14 days post ovulation.

So the question remains, When can I test? Well, much of the answer depends on when ovulation occurred and when implantation took place. If you don’t mind taking a risk and possibly seeing a negative, try testing early at 8 to 10 days post-ovulation. But remember that even if you see a negative, you still may be pregnant. If you don’t want the risk, wait until at least 14 days post-ovulation. Sometimes, but rarely, it may take up to 17 days post-ovulation to detect a positive test.