Hatch maternity navy floral dress one size fits most

This adorable dress from hatch was worn once while I was pregnant. It’s a very lightweight and feels like cotton. I couldn’t find any tags with the materials. It hits above the knee and has pockets! It is marked as “one size”. I wear a 27/4-6 pre pregnancy and wore small and medium in Hatch clothes while pregnant depending on how I wanted things to fit.