Im posting this here in the hopes that someone in the medical field sees this and is able to answer. I hope this is not too off topic for /sci/

Hey guys,

Last August I broke up with my girlfriend at the time because I knew she was sleeping with her ex for a majority of our relationship. When I broke up with her she said she was pregnant, which I completely disregarded because I thought she was trying to manipulate me. Ever since then I've been checking her facebook every couple of weeks to see if she posted a picture with a preggo belly or if she said anything on the subject.

Well today I checked and saw that she posted this picture of the ultrasound in late January saying that it was her and her boyfriend's (the ex she was cheating on me with) kid.

What I need help with is figuring out how old the baby (female) in the ultrasound is and determine if it's old enough to be my child.

Please, please, please, if anyone knows how to determine the age of a fetus from an ultrasounds I would greatly appreciate the info.