Both of my pregnancies the doctor asked me to come in well before 12 weeks - in fact at about 4 or 6 weeks when I first suspected I was pregnant.
That said, you really can start to hear the heartbeat at about 10 or 12 weeks. You can however SEE the heartbeat on ultrasound starting at about 6 weeks.
Something does sound skeevy here.
Something is screwy here, and any way you slice it, its a train wreck waiting to happen.
Personally, I hope there isn’t a baby, because a baby would be the only innocent involved. And it will be much more fun to watch the train wreck if there are no innocents involved.
If this guy is as irresponsible as you are painting him, I don’t think its likely that his newfound responsibility will last until the baby is born. And if it does, it won’t last through diapers. I really feel for your stupid git of a coworker if she is pregnant - odds are she has a long road ahead of her as a single mom. But I also feel for him if she really is pregnant - as, from your story, it has “entrapment” written all over it. Shame he would have to share a child and spend the next eighteen years writing checks to a manupulative bitch. Course I might be jaded, maybe they’ll get married and live happily ever after just like in all the storybooks.
Personally, I’d be looking for a “miscarriage” at about four months - very emotional one that would require lots of support and attention from him. (I don’t think she’s pregnant, either).