My lover is pregnant. Her LMP was June 4th. She has had her 2nd ultrasound today. The EDD is 11th March, but based on the LMP. Her cycle has always been a little irregular (completely in fact until the April, May and June). We had sex but used a withdrawal method, although I did ejaculate on the surface of her vagina, on 27th June. Please don't judge, but she is married and had unprotected sex around 18th June - which fits the 'standard' ovulation date. What chance - I realise it may not have a % but 'approximately' - is it that the baby was conceived in 27th June, given the 'withdrawal' method and the distance from the 'standard'. I do want this to be my baby as does she, but we both feel it isn't. The nurse at the 2nd ultrasound (today) said that the embryo was larger than 'expected' and growing well - I'm not sure if that lends itself to an earlier conception date or not, or, as I am western and she (and her husband) are Asian, this might make it more likely to be mine. I know no-one can 'guarantee' either way without testing but I have read some forums/used some calculators that seem to show it's an minutely small chance of being mine, but others have said you can conceive at any point...

So her last period was June 4 and she had intercourse on the 18th and 27th of June. Sorry, but it could be from either. The timing is too close to call. Calculating conception is an inexact science. While the sex on the 18th is more likely to have resulted in conception, I would put it at much more than a minute chance that its yours.

On the other hand, testing may not be required if the baby shows "western" characteristics. But it still mean you have to wait until birth to know.

I don't understand what being "western" or Asian has anything to do with conception

That said, depending on where you live, this baby may legally be the child of her husband, genetically yours or not.

Not sure how to 'add' information for my question. Apologies for the Asian/Western reference - I am clutching at straws for hope it may be mine. I realise the size of the embryo now is not relevant. Additionally, she had a blood test (not expecting to be pregnant) on July 5th that showed she was pregnant. This would have been 8 days after we had sex. Can a blood test show pregnancy that quickly.

I understand you want this to be your child, and it may be genetically, but not legally.

8 days is a little too early for a positive result.

So, based on the blood test within 8 days (she didn't have any symptoms, the blood test was for something else), the chance of him/her being mine is less?

Stop concerning yourself about this. NO ONE CAN SAY POSITIVELY ONE WAY OR THE OTHER! No matter how many factors you give us, the bottom line is the sex was too close together to rule out one or the other partner. Our answer is not going to change.

There is no way to know whether this baby is yours until it is born and a DNA test is done.