Could I be the father?

[harryzona]

Is it in any way possible for me to be the father of a baby if the baby is estimated to be 5 weeks and 5 days old on the 20th November from a scan but I had intercourse on September 15th with the mother to be? I know that 5 weeks and 5 days previous is October 9th but firstly I cannot be completely, 100% sure that the 20th is exactly the date, I can only go on what I am being told from the lady in question. I am wondering exactly how accurate the scans ability predict the exact age of the foetus is and if it is an estimate, could this estimate still make it possible for me to be the father. I have read that various factors such as a woman with irregular periods, a baby that grows more quickly or slowly than average, or a baby with a shorter or longer gestational period are just a few things that may affect the results.

The female involved assures me she took the morning after pill after the 15th but I know that this is not always successful. Also does this artificially start a new menstrual cycle making estimating the date of conception / baby's age by using period dates more difficult, which I believe were used to try and work out the baby's age in this case?

[harryzona]

Thanks a lot for your replies. This has been very helpful.

[Nichole05]

its weird but pregnancy is actually calculated from the 1st day of her last period techically before she is even pregnant, so as a standard you would take away 2 wks from da age at da scan and at da end of that 2 wks would be about when she concieved. Sperm can live inside the vagina up to 7 days so that would give you like a 7 day span on either side of her ovulating. Ultrasounds are more accurate in early pregnancy than later but are also based on a standard average percentile. but what it all boils down to is if you are not completely sure and dont think things are adding up ask for a dna test once the baby is born

[Eirlis]

I highly doubt you're the father if the gestational age was that low at the end of november. Keep in mind that gestational age starts from the last menstrual period, so the actual conception date is generally around 2 weeks later. That would make conception most likely in mid october, not september. Ultrasound scans can be off by a week or so, but generally not much more than that.

Still, the only way to be 100% sure is to do a dna test when the baby is born. Good luck. =)

[spade22]

Ultrasounds when performed in the 1st trimester are usually accurate to within a couple of days.

Pregnancy is dated by adding 2 weeks to conception date (or more commonly from the last monthly period if a women has a regular 28 day cycle).  If the baby's gestational age was 5 weeks and 5 days on 20th November, that means she conceived 3 weeks earlier (end of October/beginning of November).

Based on what you have said, it is very unlikely that you are the father (she would be closer to 11 weeks and an US will not be off by as much as 5 weeks) but no  one can say this with 100% certainty.  A DNA test can be performed when baby is born is paternity remains in question but in my opinion, I do not see how you could  be the father from the information you have provided.