Curious.

[newmompink]

I'm 35+4 pregnant. Due August 25. I thought your pregnancy goes by your LMP & cycle. Okay my LMP was November 15, 2012 my cycle is 34 days. I had sex with my ex November 26 & 28. Then had sex December 3rd with my boyfriend. I know this sounds confusing but who would be the father? Both men know about the situation & are happy. But its urking me.

[AnnieBrooke]

Unless you can find the report of the ultrasound that was a while back and find out when it was:  i.e.; how far along you were in your pregnancy when you were given the due date of August 25; all the dates you're listing are going to have margins for error big enough to make room for either guy to be the dad.  The ultrasound is your key here, it needs to be ruled out or in as far as being reliable for dating.  It is quite plausible you ovulated early or late, but the ultrasound measures the embryo quite precisely, and that is what will help you here.

[newmompink]

I'm having a girl. I can't remember my first appointment but my doctor went by my LMP without using my cycle days which would make me 36weeks as of today.But when I got a ultrasound a while back my due date was 8/25/2013. Okay I understand about the calculations you got for ovulation but sometimes ovulation dosent occur when your really suppose to ovulate. I was noticing signs of ovulation on the 26 & 27 it was that clear stretchy cervical mucus.

[AnnieBrooke]

Well, your problem really is that if all the sex was unprotected, there were still live sperm in your system from November 28 when you had sex on December 3.  It's pretty hard to rule out anyone when both men's sperm were there at the same time.  Is the baby a boy or a girl?

The length of the cycle is only useful if you don't have an ultrasound -- you would do a computation sort of like this:

    ovulation to the first day of the period: 14 days
    my cycle: 34 days
=
    projected ovulation date in a given cycle:  day 20

This is basically an educated guess based on how ovulation leads the next cycle, and the calendar.  Using that method, ovulation would have been around December 5.

But, if you have gotten an ultrasound and your doctor gave you the due date of August 25, AND if the ultrasound was early enough in your pregnancy, it is going to be more reliable than a forward projection by the calendar from the first day of the last period.  This is because women don't ovulate exactly by the calendar, and because the ultrasound saw and measured the actual baby.  The conception calculator gives the following for your due date of August 25:

Probable date of ovulation:  December 2
Possible dates of conception:  November 28 to December 6

Due date:  August 25 (40 weeks)

At what point in your pregnancy was your first ultrasound, and what estimated due date (EDD) did they give you then?