Another u/s accuracy question

Searched and found a similar question, so I probably know the answer already but it helps to be reassured.
My ex g/f slept with someone not long after we broke up, found out she was preg and married the guy.
She went to the Dr. who did a blood test and said she was a week preggo, so at that time there was no doubt who the father was.  Now months later, the Dr said on Tuesday (Aug 4th) she is 18 weeks.  That date now would show me as being the father.  I've read and understand that the farther along, the more inaccurate the u/s are for giving the date of conception or what not.  (Sorry if I don't know all the terms)  
The Dr does not know that there is any question as to who the father is.  The husband is now up in arms over this and is making an issue out of it.  Whether im the father or not I don't want to stress her out but im also trying to help out as much as I can.  Her biggest concern (besides the social nightmare this is) is that what if there are health issues with the baby (its a boy) when its born and they have the wrong family history (the husbands and not mine).

I guess there is nothing to do but wait.  Her due date was Jan but keeps getting pushed back, its now Dec 31st.

[FLnative78]

She is already feeling movement from the baby..can that be placed into a time frame as well?  This is her first child.

Sorry if this is in the wrong section.

[FLnative78]

One more thing, she was on BC for years, and then off for about 1.5 years about the time we started dating and during that 1.5 years she has never had a regular period.  That also was making it hard to figure out the date.

[TristynsMama1oh1]

First of all, I'm a pretty blunt person so I'm sorry if I offend you but I think your ex girlfriend is stupid. Why would she marry someone just because she's pregnant? I know that's not the question here but that's sorta annoying to me because its like women dont know their own strength and they think they have to have a man so they can fit into the social stereo type of being a happily married mommy and daddy.. I was married before I had my children so dont get me wrong I do believe that its better that way but I dont think anyone should get married just because they are pregnant, that only makes things harder for the children when things dont work out. Anyhow back to your question.. Yes ultrasounds can be wrong but nowadays they are a little more accurate then you'd think, so ultimatly if the ultrasound is saying that she is farther along she more than likely is and you are more than likely the father. But why not just wait until the babys born and do a blood test. Simple and discrete no one but you and the girlfriend and the husband will know (besides the doctors) and your social standing wont be compromised unless someone spills the beans. Good luck! Sorry if I'm no help at all! lol

[FLnative78]

Oh believe me the marrying him for that reason has come up a bunch, but that's for a different post (I do totally agree with you).

I did talk to her again and she went back and looked at her 8 week u/s and that showed a EDD of Dec. 25th.  Now the one last week showed her as 18 weeks and a EDD of Dec 31st.

I don't know if this helps with the dates..but the last time her and I were together was March 29th (we think, but definitely not after the end of March).  Her and the new husband were together around April 15th.  I don't know how long the whole process is from ic tell whatever happens.

Ultimately there is nothing we can do but wait and do the test when the baby is born.  I'm just trying to settle my mind some as I'm stressing over this, although I have to say that I'm actually very excited and would love for the baby to be mine..which in turn is a hefty blow if its not.  Another reason I'm just trying to get a better idea if I'm the father, is because I don't want to miss out on anything that's going on with the baby.   Aside from the sh1tstorm this may create if it is mine.  And all this may be for nothing too.. and we may find out they were off and it is his.

[FLnative78]

You'll have to excuse me if I post alot to myself, im just thinking out loud..but
If she found were to have gotten preg the middle/end of April then that would be a late Jan EDD correct?  

[AnnieBrooke]

Conception for a December 25 due date would be at or around April 4, and for December 31 would be at or around April 11.  Unfortunately, that doesn't exactly let you off the hook, because sperm can live in the woman's system for up to 4 or 5 days.  If you had sex at the end of March, the baby could be yours, especially if she ovulated just a day or two earlier than an "average" cycle.  You're going to have to do DNA testing to work this one out.  

[FLnative78]

Wouldnt 9 months from the middle to late April be a middle to late Jan EDD, or is that not how it works?

[AnnieBrooke]

The length of a full-term pregnancy is 266 days from conception to birth, or 280 days when counted the medical way (from the first day of the last period).  So if you were hoping it was a conception date of, say, April 15, the estimated due date would still be no later than January 4.  

You can't really count by months on the calendar, since our calendar months are all different lengths.  To be more exact in your figuring, use one of the many pregnancy calculators online, or count out the days (not months) on a calendar.  (Believe me, the pregnancy calculators are less tedious.)  

Using a pregnancy calculator, I checked backwards from your ex's two possible due dates given by the ultrasounds.  As I said above, they gave a conception date (for the 12/25 due date) as April 4, and a conception date (for the 12/31 due date) as April 11.  If you add maybe 4 to the April 11 date to represent the "middle of April," you'd come up with the due date of January 4.

Given all the ultrasound information so far, an end-of-January date would be wildly overdue.  

[FLnative78]

Well im learning all kinds of stuff, if he's not mine I'll be well prepared for when it is my time.
Thanks for the help!

[FLnative78]

Well she went to the Dr. again this Tuesday (Aug 11th).  Dr. is giving the official EDD as the 25th of Dec.