<human>: the first time I had sex with my girlfriend was 83 dags ago and the ultra sounds pictures shows the age of the foster (babe) 89 dags. and that means thereare  6 dags lost I mean I didnt have sex with here at that time, and I am really in doubt about being the father.I need an advise if the ultra sound can make mistakes about giving the exact right age.hope to hear soon from youbest regards
<bot>: Hello, I have gone through your query and here are your answers: firstly, the age of any pregnancy is determined clinically from the first day of the last menstrual period. Secondly, the gestation age in sonogram also is determined on the same basis; a pregnancy detected one week after the missed period is considered as 5 weeks gestation, counting from the last menstrual period. So, based on this, it is more likely that YOU are the biological father. There can be a variation of 3-4 days in a very early pregnancy in a sonogram as this is the period when the age of a pregnancy can be determined most accurately. Hope your query has been clarified.