Around week 14, my regular pants starting getting too tight. This was a lifesaver. It allows you to keep your pants up, yet conceals the fact that they're not buttoned. I was nervous it would be noticeable but it hides it well and holds them up, without being uncomfortable.
Around week 25, I was in maternity pants but as maternity pants can droop (especially the jeans), this helped keep them up. Again, comfortable. I wore this until the end of my pregnancy, and it always looked like a white T-shirt underneath my maternity top.
Postpartum, this was also a lifesaver. For the first three months, I still had to wear my maternity pants unfortunately, but obviously the only way to keep them up was this band. Then when I began to fit back into my regular jeans but wasn't quite there, this helped me keep them closed until I could button them again.
This is a great product for all maternity stages and it's really a necessity. The only thing I would recommend, if this price seems high, is to check out other knock offs. For example, Target makes a band similar to this that is supposedly much less expensive though I have not tried.