This may sound stupid, but bear with me for a moment-I wonder if, legally, one was considered an adult at the age of 19? I think it was some time in the '70s when you became an adult legally at the age of 18-it was in the '70s when you could vote at the age of 18 (prior to that, you had To be 21). This was true for signing a contract, too. I suppose I am nitpicking, but I don't think Jan was considered an adult in 1973, at the age of 19. In any event, that may have nothing to do with her disappearance, and has nothing at all to do with the possibility that she may have had more than one prospect for the father of her unborn child. She may very well have had more than one boyfriend (not judging, either...). For some reason, I doubt it-no good reason to think this, except that it is more common to have only one. Plus, the cold case detective wants to talk to this Eric Shore, and doesn't know where to find him-I guess he thinks this guy might have been the father.
Edit-turns out the voting age was ratified in 1971-
I'm not sure what the laws were. I think you could drink at 18 then couldn't you? I believe if Jan was a runaway at 19 the police wouldn't have picked her up, so in that way she was an adult. And she would be considered old enough to handle her own relationships, jobs, etc. But it seems like I remember my mom saying she had to sign for my brother to get married in the 70s and he was 19 when he got married. Did someone have to sign for you if you were under 21? I was very young then and don't remember.