By the way, the first ultrasound was done showing baby to be 8 weeks and 5 days.
The ultrasound is likely more accurate, but also remember that it's an estimate.
I agree with maw, ultrasound a little more accurate since they use your last period to calculate due date and not everyone is regular. And also the ultrasound can be off too since babies develope a different rates throughout the pregnancy sometimes measuring bigger or smaller. The only way to he sure is a paternity test which can be done later during the pregnancy or once baby is born (they even sell kits over the counter now I believe)
It sounds like you are the father. There are many factors that contribute to the due date being an estimate, how long s perm can live before ovulation occurs and fertilization talked place-up to a week, how long it takes to implant 5-12 days, how long her luteal phase is. It isn't like you are talking about a months discrepancy. It sounds like you and your wife need to communicate better to reestablish trust in the relationship. Better to do it now before baby is born and it leads to more developed problems. A baby with two parents has a better chance at life. Don't let fear control you, suspicion is fear.
Remember that the due date is an estimate! Baby could also be measuring a little ahead or behind. My baby always measuring larger than what my "due date" was.
When you say "My wife is showing as being 10 weeks and 3 days pregnant / that makes the conception day the 7th of October" you are wrong. If she is at gestational age 10w3d on the 17th of December, conception would be around October 14 - 24. Her last period should have come around the 5th of October.
When a doctor gives a gestational-age count, he is NOT counting from the conception date. He is counting from the assumed first day of the last period, which comes two weeks before conception. A doctor saying you are 10 weeks 3 days "pregnant" means you are 8 weeks 3 days from conception.
If you don't understand this, call the doctor and ask. Pregnancy is calculated from the first day of the last period because in grandma's day, that was the only signal they had to begin the count.
Get a copy of Your Pregnancy Week by Week, or A Child is Born, or any pregnancy book, and they will say things like "6 weeks pregnant (4 weeks from conception)" alll throughout the book. Or just look up "gestational age" and see how it is calculated.
As the previous poster says, suspicion is fear, don't be fearful. If you have a genuine reason to think your wife has been with someone else, talk to her and find out. But the g.a. of her pregnancy is not that reason. It leads to you as a perfectly plausible candidate for dad.
ps - When was the first ultrasound done, that showed the baby to be 8 weeks 5 days? On what date (on the calendar) was that?
Thanks for the feedback everyone.
It is great to know that there is a huge chance that I am the father. From what doctors and midwifes had told me it was a very small chance.
No, from what you thought they told you, you had a small chance. Not from what they told you. They were speaking in medicalese, and thought they were being clear. Another doctor or nurse would have understood immediately that they were using a GA, which count begins on the first day of the last period. The problem is, medicalese sounds just like plain English. They spoke in medicalese and you heard it in English, and nobody realized the other was misunderstanding. I am SURE they did not say "You have a very small chance of being the father," and am sure you didn't say "Do you mean CONCEIVED on October 7?" It would have never occurred to either of you to say these things, because you thought you were understanding each other.
Anyway, it sounds (if the ultrasound was on December 10 and said 8 weeks 5 days) that the baby was conceived December 24, give or take a couple of days.
Have a merry Christmas!
sorry, conceived October 24, not December 24! Wish there was an edit function. lol