Use a Standard Lens
A standard lens – something like a 50mm on a full frame camera – is one of the best maternity photography lenses because it offers you so much versatility in what you can do.
You can get in close, take a few steps back, easily get high-angle or low-angle shots, and much more.
What’s more, standard prime lenses offer excellent sharpness, minimal aberrations, and great low-light performance due to their large apertures.
Standard lenses also capture the scene in a manner that closely resemble what our eyes see, so the images taken with these lenses look natural.
You can certainly use other lenses – longer focal lengths offer beautiful compression, for example – but for me, it’s hard to beat a 50mm prime.