Realistically, the most reliable result comes from taking the test after your period is due or late. We understand though that you more than likely don't want to wait that long , however once you fully understand conception and how a pregnancy implants you'll see why it's important to wait as long as possible.

Once an egg is fertilized, it takes 7 to 10 days for it to implant in the walls of your uterus. When the fertilized egg is imbedded, it then begins to product HCG which is the hormone that pregnancy tests try to detect. Each day the implanted egg produces more and more HCG and the higher that HCG level gets, the easier the pregnancy test can detect it.

All pregnancy tests vary in their sensitivity levels. The lower the mIU number, the better the detection is of HCG. Some pregnancy tests can detect as little as 20 mIUs and others up to 150 mIUs. The lower then number, the earlier you can take the test. If you are using a 20 mIU pregnancy test you may be able to pick up some HCG around 8 days after ovulation although most women won't be able to get a positive result until 10 days after ovulation.

Things to remember:

1. Sometimes a fertilized egg will implant and begin to produce HCG, but then cease to develop. The HCG can take some time to leave your system and this could result in a false positive pregnancy test. This is one more reason to try to wait until your period is late.
2. Pregnancy tests are very precise in their reading time. If you wait too long to read the test, you could begin to see evaporation lines from the test decomposing.
3. The egg doesn't always implant before you're expecting your period, so if you test on that first day, you may get a false negative result.
4. Research shows that 10 percent of pregnancies weren't detected when lab tests were done the first day of a missed period. OTC kits, which are less sensitive, may miss as many as 25 percent