Blood Drug Testing

How many hours should pass for a pregnancy blood test to become 100% accurate?

My girlfriend and i had intercourse yesterday at 5 o'clock in the afternoon. is a blood test for pregnancy accurate tomorrow morning?? (After 40 hours or so) please answer if you are completely certain. Thanks! I read the first answer. if that's the case what are these baby checks in the market. there is one brand that claims it shows if you're pregnant after 24 hours. Are they all B.S? By the way, my girlfriend should get her period 4 or 5 days from now. I mean something like 5 days is remaining based on her calculation.

Public Comments

1. Hours? Try weeks. A pregnancy test won't show positive until at least 12-14 days after conception. She might not have even conceived yet if she wasn't ovulating yesterday. . . sperm can live for 5 days in some cases. Wait until her period is due, if she misses it, then she should take a test. If her period comes, then she isn't pregnant. **Edited to add: Sorry that I missed "blood" test in your question at first. A blood test can detect a pregnancy after about 7-10 days. But most doctors don't feel the need to order the test (expense) and will have you wait until you miss a period and take a urine test. There are NO tests which will detect pregnancy earlier than the blood test at 7-10 days. There are some home pregnancy tests (urine) which claim to be able to detect pregnancy 5 days before your period is due, but honestly they have variable results and many women who are pregnant don't get a positive result that early because the hormones haven't built up in your system enough to detect. So I still recommend waiting until she misses her period if you want to have a more accurate result.
2. No. You have to wait until she has missed a period to do a test, otherwise it will come up negative.