concerned about my due date/conception date

[babykaisen]

i found out I was pregnant unexpectedly. with my periods being irregularit's hard for me to pin point any actual dates. i was given my first ultrasound Oct 26 and messured 15w and some odd days. with that measurement she gave me the due date of April 15 and a conception date of July 20-24t. what is the change of my due date/doc being accurate? me and my ex split up and I had itercource in july with a new parter but don't remember the date we had sex. me and my ex got back together July 15th and I was given the conception date of July 20-24 does this mean it would be my exs? please dont judge and no rude comments thank u

[AnnieBrooke]

A baby is conceived, it's one cell, and the next day it splits into two, and then the next day four, and then 8, and so on at a pace that is understood by medical science.  But after some time goes by, due to their genetic heritage and the health of the mother and the amount of nutrition and other factors, some babies will grow faster and some grow slower than the "average."  Some babies stick with the averages for their number of weeks pregnant the whole pregnancy, but the doctor will assume that the 12th week ultrasound is showing a baby that is 12 weeks plus or minus 7 days, and by the end of pregnancy the margin for error is 3 weeks.  If you had said you got your ultrasound in the 6th week, your margin for error if you were to use it for dating the pregnancy would only be about +/- 1 day.  But by your 40th week, it's +/- 3 weeks if used for dating.  So your 15th week pregnancy is probably something like +/- 12 - 15 days, meaning it is not going to be precise enough to determine between the unknown July date guy and the July 15 guy.

[AnnieBrooke]

Hi, with the first time you had an ultrasound being so late, it is not possible to rule out anyone.  Not long to wait now, you can get a DNA test when the baby is born with both men.

[babykaisen]

so that means my due date could not be accurate with the messurements of the baby?

[babykaisen]

and how come the time of the ultrasound has anything to do with the accuracy?

[maw4389]

Only way to know for sure would be to be honest with both of them and do a dna test.