Unless you already have seen the blood, then it
Would be after. (sorry if I'm confusing) the way it works is ovulate-bleed-ovulate-bleed-ovulate-bleed. A period and/or ovulation while pregnant isn't possible.
You conceive before. A female will always ovulate before she ever experiences a period and this is why young girls who have yet to see a period can become pregnant before it happens.
Most women concieve about 10-14 days after, keep in mind that everybody is different. But you pregnancy starts counting the first day of that period.
You conceive after. A period is the shedding of the uterine lining, and if you're pregnant, the uterus can't shed. You may have some bleeding after pregnancy is achieved, but it's most likely light spotting caused by implantation or something else. Hope this helps!