I know the only way to tell 100% is a test, but until then we'd like to know what you guys think. You're well versed in ultrasounds and the like, right?
Someone I know had her dating ultrasound on March 25, and it dated the pregnancy at 13 weeks and 1 day along with a due date of Sept. 29.
She last had sex with this guy on Dec. 21. She's not sure if she stopped before that, but definitely no later.
So, what do you think the chances are that he's the father? Remember that ultrasounds at 13 weeks can be off 8 days (as far as I know, what have you read?), and sperm can be found in the woman's system for up to 7 days.
Her current due date gives her a conception date of around Jan. 6th so if that's accurate it's impossible, but we want to consider worse case scenario with ultrasound being off the maximum days and sperm living 7 days as well.