If it were me, I'd remove InTeen and see if the birth would then proceed normally.
I've never seen a glitch quite like that. Not sure what the solution to your sim's problem is. Did you back your game up before installing it? If you don't have access to these options, InTeen may indeed be what you need, but make sure you get the version that's compatible with your game, if you haven't already. (If a pregnant sim eats cheesecake, twins result.) On the other hand, if you do have OFB, you've got not only the cheat, but cheesecake as well. I think forcetwins came with OFB, though, so if you don't have that EP, you may not have access to that cheat. The cheat you want for that is forcetwins, and I don't think you have to be in debug mode (have the boolprop cheats 'on') for it to work.
Second of all, I'm not aware of what boolprop testingcheatsenabled true has to do with twins. Especially when we're talking about one as complex as InTeen. Well, first of all, a 'Hey, why not.?' attitude toward adding hacks to your game is unwise.
