<blockquote><b>Quoting snglemama:</b>" nurses are (the good ones anyway) good about not commenting on obesity, or how difficulty someone ... [snip!] ... heart rate on an obese person... assisting them in holding legs up is hell.. especially with an epidural. but.. we do it."</blockquote>
My mum is a diagnostic ultrasonographer and she says that it is almost impossible to get any clear image or trace on a woman over about 30kg overweight. The vast majority of missed severe defects are in obese women, because ultrasound doesnt travel through fat well at all.