Is VERY Small Platy VERY Pregnant?

Hello there, I've not found a direct topic covering both aspects of this question so I'm sorry if it's been raised before by someone, elsewhere... I have a 7 month balloon platy (she was born in the tank, along with one other surviving baby female of the same).  While they've both been very happily swimming about & looking and eating well, they've only grown to approx. 1/2 inch, to date (head to tail tip, so even less if you don't count the tail) - I figured they would be bigger by now, after 7 months?  The adult balloons are, of course, quite small to start with - around 1 1/2 inch (head to tail tip) but I thought the babies would be bigger by now?  Anyway, just to complicate things, one of the 7 month has developed (in the last 24 hours) what can only be described as bulging white roundish shapes coming out from underneath her - right where platy babies come out.  So, is she pregnant and trying to give birth?  Is it normal to see the beginnings of fry coming out, before they actually start coming out (if you know what I mean?)?  I'm just worried that if she's abnormally small, and she is pregnant, could there be some difficulties going on here, i.e. too small for the fry to come out and are getting stuck, or is that a ridiculous notion on my part?  Tank water is consistently good for Ammonia, No2, No3, pH & KH,and regular cleans and W/Cs... All platys feed well, so I'm not sure whether these youngest Platys should be bigger than they are, and if the one with white bulge is pregnant?

If anyone has any ideas I'd be very grateful for your thoughts/suggestions - I'm only about 1 year into fish keeping so very new to this 

Hello Sue, yes they are very much attached, and do look 'egg' shaped (and I totally get what you mean).  I haven't been able to witness anything dropping away, since I noticed it yesterday (definitely wasn't there the day before that).  I did wonder if 'whatever' she is trying to 'pass' is too big for her - oh dear.  I can only keep an eye on her and 'hope' she can get them out.  We didn't think through the 'balloon' distortion side of things, when we first got them, last year, but it's a very good point  . Thanks very much for your reply.