Can pregnancy test be positive 3days after sex?

Hello
Thanks for writing to us with your health concern.
Yes, if you had sex around the time of ovulation, you could have a value under 50 within 1 week of sex, and it can be positive.
All the best.
Please feel free to discuss further,
Regards.

I have been searching online and I am not sure how you can have a positive test in 2-3 days after sex?? I thought a test is only positive after implantation. Please help to understand the process further.

Okay
Let me explain.
Implantation occurs around 5 - 10 days after fertilization, it can be as early as 5 days.
Generally , at 3 weeks from LMP, the levels from 5 -50 are considered normal for early pregnancy.
It is possible that you might have had early implantation , around the 4th day itself.
I am just going by normal values for a probable early pregnancy, at 3 weeks from LMP.
Please go through this link -
http://www.early-pregnancy-tests.com/blood-pregnancy-test.html
Of course, values lesser than 25 should be re confirmed after a gap of 5 days.
Take care.

Thanks. Here's my dilemma. I was going through fertility treatment-- on a drug called Metrodin. LMP was 3/10. I had IUI on 3/24. Unfortunately, I had a sexual encounter on 4/2 and found out from a urine test on 4/4 I was pregnant. Blood test confirmed on 4/5 Hcg 24. Based on this additional information is it likely the encounter on 4/2 resulted in a pregnancy? I had another HCG test on 4/9 and it was 72 and I was experiencing ovarian hyper stimulation as well.

Frankly it could be from either of the encounters.
You will have to wait for a few more days until you are atleast 6 weeks pregnant when a dating scan would be done.
Based on the dating scan, you would know when exactly you conceived, though even dating scans are off by 5 - 7 days.
If you had IUI on the 24th of March, you would be 5 weeks pregnant on the 5th of April, and the levels should be more.
Are you talking in retrospect, since it is not yet April !! ???

Yes.. Speaking in retrospect. When I do the calciulation I should have been 3weeks 5 days on 4/5. How do you get 5 weeks? LMP 3/10 and 14 days later would be 2 weeks 3/24 when I had the IUI and then my encounter was on 4/2 9 days later-- I thought I would have already ovulated by then. I saw online where the median hcg level at 3 weeks 5 days is 25.

My mistake.
I did not know for sure all this was retrospect.
Of course, you would be 3 weeks 5 days on the 5th of April.
SO yes, most definitely you conceived from the IUI.
There is no way that you had intercourse on the 2nd of April and had the level that was observed on the 5th.
It is less than 1 % likely, and 99 % likely that you conceived from the IUI.
You would have had pregnancy scans, can you please upload the earliest one ?
That will be very conclusive.