The most important aspect to consider when choosing a photographer for your most precious and important little bundle of joy is whether they are going to handle your baby safely. Most of the photos you see on a professional photographer's website will be edited a little bit. This means that if a pose looks a little unnatural or dangerous, the likelihood is that it isn't what it seems and probably is a composite image. A composite image is an image that is created from merging one or more photographs and manipulated to look like one photograph.
One has to be especially careful with newborn photography as babies under about 1 month old are unable to hold their heads up. A big red flag is if a photographer attempts to 'balance' a neborn to quickly get the shot. Personally, I won't do poses such as the 'froggy' pose (moving the baby's hands to look like they are holding their own heads up) without a trained assistant. I will write a seperate blog specifically for newborn posing later on, but for now lets have a look at some basic techniques for safely posing babies.
On top of lone or unstable objects
There are two ways we can go about achieving this look. Either with baby being fully supported by mum or dad, or with her not being on the object in the first place. One way to do this is by manipulating and merging multiple images together as described above. The other way to do this is to take a seperate picture of baby in the correct position and completely replace the background to look like baby is sitting on a chair alone when actually they are on a mat on the floor.
At the end of the day, you will get a feel for what is safe and what isn't. If you are doubting your photographer's ability to safely pose your baby, then make sure you are vocal about it as you are the one hiring them. It's always better to err on the side of caution and to not let anyone do anything with your baby what you wouldn't feel 100% comfortable doing yourself at home.