Okay, a couple corrections here for starters. I have to say that the first two are actually not SUVs at all and in fact, the Fiesta is somewhere closer to a hatchback more so than a standard sedan. The Subaru, I'm pretty sure, is somewhere around the likes of a wagon. The RAV4 would be the closest to resembling an SUV and is actually are the smaller end of this anyway.
With all that clarified, were you looking for the SUV with concern to where you live and the weather? If not, I would definitely go with a smaller car, but, maybe a sedan somewhere in the size range of a Honda Accord or Toyota Camry/Corolla. They both get a lot of press but both car brands are extremely reliable and will likely carry you for several children to come. They also have more than enough space for baby in the back. The Fiesta is a bit small, and quite honestly I don't know their safety rating. American cars in general tend to be a little bit less reliable than foreign (unfortunately) but sometimes their price is a little more appealing at first.
I wouldn't get an SUV unless you have some extreme weather where four wheel drive is needed. Some sedans even offer all wheel or four wheel, but they just aren't as high height wise. A RAV-4 probably wouldnt even be a good idea if thats the case since they're not much bigger than a wagon. If you decide on a larger more standard SUV, get ready for the gas price because it is with any larger vehicle much higher. Most generally also have a much lower MPG rating as well. You'll blow through gas money faster than you might think.