That's a point Shades, I only found out recently that thats why I always had to have internal scans, normal scans didn't work. I thought it was because of my weight but the doc said it wouldn't matter if I were Angelina Jolie, my uterus tilts away from the scanner
All the scans done at the IVF clinic were internal anyway, so I never knew that could be an issue! I think I was nearly 10 weeks pregnant before I had a regular scan instead of an internal.