Is this a maternity top as well? Will it fit in the last trimester? Or is it just an early pregnancy and postpartum shirt?

This top is classified as an "infinite" fit top in that it can be worn during and after pregnancy. The material is stretchy, so it may accommodate you in you last trimester - that would depend on the size of your growing belly and your personal choice as to fit. Go a size up for a more relaxed fit.