I always said "Ob/Gyn" (pronounced obb-gin). Last I heard, they were using ultrasound. You can see quite a lot on those *if* you get a good ultrasound tech. And when you're pregnant, they have you coming in to visit pretty frequently -- every month at first, then every other week, then every week as you get close to your due date.
When I was pregnant in 1997, I only had one ultrasound scan, at around six months. When I was pregnant again in 1999, I think I had three. It wasn't a routine visit thing.
They're doing some pretty incredible things with 3-D ultrasounds these days, but they're pretty new -- don't know the timeframe of what you're working on.
Everybody's different, mileage may vary, etc, etc
PJ