If you use what is familiar and you are confident in, you will be more confident and probably take better photos. That's probably the overriding factor.
I would shoot MF if at all possible, i.e. if there is enough light. Most hospitals allow you to shoot with bounced flash (it can startle the first couple times but is harmless: flashing for f/8 EI400 is 1600 times less light than a second in full sun but somehow we still have a huge bitchfight on APUG about it occasionally) and that's what I did when my daughter was born.
In terms of finding Portra washed out, was that a scan or an optical print? They both scan quite differently and need different scan settings to render properly. I find the Fuji films far easier to scan accurately (and I suspect they handle fluorescent light better with less green tinge) but if you nail the scan of the Kodak, it will be just as vibrant etc and of slightly finer grain. They both print beautifully to RA4 paper.
Just don't use Ektar or you'll end up with a picture of a wrinkled beetroot. I'd also suggest taking some B&W film too, e.g. TMY2. If you're shooting in a hospital and not flashing, or trying to balance flash with ambient, the lighting will usually be a mix of horrible colours and B&W will hide all of that.
Pro 400H has dropped darker tones on me so many times.. even in even lighting has dropped out dark hair to simply nothing.. Portra 400 has never failed me. In terms of grain Portra 400 is significantly finer than 400H I've found. An optical 8x10 from 6x7cm Pro 400H, and Portra 400.. the 400H looked like it was from 35mm. I could never go back to 400H.
I never had much of a problem with 160S, really liked it. I do prefer Portra 400 to Portra 160 usually.
Thanks guys. I'll go with some Portra 160. The baby is 3 months now and been home a while. They have a new house with lovelly big windows and big rooms so the light gets difused arpound the room nicely. Before they asked me I was sat in various rooms in their house thinking "I'd get some great photos in this house with this light" and then the question arose :-)
Funny the issues raised about 400H - I am having problems with some 800Z but that is a new thread I am about to open.