gestational aging

[hjustin04]

My girl friend has had 2 ultrasounds they Are both agreeing that she is 20w5d. Her blood work shows she should be in the 19th week. However she told me her LMP was December 16th 2010 and it ended on 12/18/10. Which doesn't sound right to me.  I wasn't with her at this time it just sounds really short. She was with her ex from 12/24/10 to 12/28/10. We got together on 12/31/10.  She is saying there is really no chance this little girl is mine. I want to know if since the ultrasounds agree and they were taken a month a part which is more likely the correct dating of the child. The ultra sound says she would of had her LMP on 12/23/10

[hjustin04]

Ok thank you

[alaysha]

Ultrasounds that late in pregnancy wouldn't be accurate. Ultrasounds for dating purpuses are only accurate in the first trimester after they they can be weeks off. Only thing you can do is have her get a paternity test once the baby is born since the dates are so close.

[hjustin04]

She had 2 one at what they said was 15w1d and the other at what they said was 19w1d. They were exactly 4 weeks apart

[hjustin04]

Ok so she could have ovulated later or the baby may be smaller is what I think im understanding. From the comments

[hjustin04]

Ok I just know she had blood work done and the they changed the date to 10/9/11. The original date was 11/5/11. And the ultrasounds gave the date of 9/29/11. These are all due dates in the order they gave them to us

[AmyG89]

Babies grow at different rates. Blood work does not tell you how far along she is and most ultrasounds are not exact.  Personally, my ultrasounds have always shown my baby to be measuring 6 days ahead. She could have ovulated either earlier or later then the "average" 14 days, I ovulated on Day 12 and I know for a fact that is when we conceived this baby since I was tracking it but there are many factors that can cause dates to be off. Early or late ovulation, sperm can live inside a women for up to 7 days, and It takes a few days for implantation to occur. So all these factors cause a difference in dates. At this point in her pregnancy, an ultrasound measuring within 2 weeks can be completely normal. If she had a dating ultrasound at the beginning of her pregnancy then that would be more accurate than an ultrasound at this point in her pregnancy.

[texasangel343]

I've never heard of blood work in later pregnancy telling what week a woman is.  Even in the beginning there is such a wide range the only way to tell is ultrasound.

[hjustin04]

Could  the 2 ultrasounds and the blood work be off that much

[hjustin04]

I think she's just scared and. And maybe thinks if she's not mine I wont still love them both.  And instead of talking she ran now. Instead of getting hurt later.  Or she thought it might hurt me so to take be out of the equation was easier in her eyes.  

[AmyG89]

Since she was with her ex on the 28th & you on the 31st it is impossible to tell who the father would be. If her LMP was on the 16th, most women ovulate approximately 14 days before the start of her next period. If she has an average cycle length of 28 days, ovulation would occur around Dec. 30th - Give or take a few days.

Long story short, it is impossible to tell without a paternity test. I don't know why she is saying it's impossible for you to be the father. If these dates are accurate, it's very possible.

I would request a paternity test when the child is born.