Who is the dad?

[Msmith1723]

I had sex with two different men in a short period of time. As time gets closer for my delivery I’m growing more concerned that I may not know who the dad is. I am currently 26 weeks pregnant. According to the ultrasound I had done my conception date would be June 22nd and the second guy I slept with was on June 30th. Being that the ultrasound said it was the 22nd made me feel as if it was the first guy for sure but now I am getting more concerned that maybe it’s wrong and could be the second guy. Is there a chance it could be the second guy or am I just getting paranoid?

[AnnieBrooke]

Well, it depends on when in the pregnancy your ultrasound was, and what your due date was that you were given by the ultrasound. If you would answer a couple of questions, we might be able to figure out if you've got it right or if it's questionable.

You slept with the first guy, what  dates?
You slept with the second guy June 30th only?
You got the ultrasound (that gave you a conception date), on what date?
What estimated due date (EDD) did that ultrasound give you? (Not what conception date)

[Msmith1723]

The first guy a few times before June 22nd so I wouldn’t know the exact date. Yes I only slept with the second guy on the 30th only. I don’t remember the exact date I got my ultrasound done but I was 6weeks along by then. My estimated due date is march 29th

[AnnieBrooke]

And you didn't have sex with anyone the week of July 1-8? For a March 29 due date, the window for sex that would produce a pregnancy is the first week of July. If the sex with the first guy stopped after the 22nd, he would probably be out of the running unless his sperm lived an unusually long time in your body. Here's from a conception calculator:

Due date March 29, (2023):
  Most likely conception time frame: July 4 - July 8 (2022)
  Most likely dates of intercourse that led to the pregnancy: Jul 1 - July 8
        

[AnnieBrooke]

I should clarify. You had said "According to the ultrasound I had done, my conception date would be June 22." But ultrasounds don't tell you a conception date, which made me wonder if you were confusing the beginning point of the weeks pregnant (given to you by the ultrasound or doctor as "6 weeks GA") for the date of conception. When an ultrasound, or a doctor, nurse, medical textbook or "What to Expect When You're Expecting" talks about "weeks 'pregnant," the count begins on the first day of your last period before you got pregnant, not on the presumed conception date. If the doctor or tech were to have said "You're 6 weeks pregnant," if you had asked "Does this mean I conceived 6 weeks ago?" they would have said, "No, you conceived 4 weeks ago." The GA count stretches back in time two extra weeks, to calibrate to the first day of your last period and begin the pregnancy count there. This is done for historical reasons (before there were ultrasounds, the count always began on the first day of the last period because that was the only signal available.) And it's still counted out that way. Pregnancy from conception to full-term birth is 38 weeks, but a 40-week count is used for pregnancy, including the first two weeks that are after the period begins but before conception.

What it means in your case is that (given your due date and that you're in your 26th week now), sex from the first week of July, not the next to last week of June, almost certainly produced the pregnancy. Men's sperm can live a few days in your body, but not 10 days or more.

You haven't said whether you had sex again with the first guy after June 30, so it's not possible to make a blanket statement that your due date rules him out. But if you didn't have sex with him after the 22nd, he does sound ruled out.