How many hours can you work before universal credit is stopped?

Before and whilst I was pregnant I worked 40 hours but had to quit due to illness so I have been claiming universal credit.

I hate not working and I’m ready to go back but I know I won’t be able to work many hours as my baby is only 4 months and also my illness. I was hoping to work between 15-20 hours or less until I can go back full time.

How many hours can I work before my universal credit is stopped? Once baby is a bit older and I’m better I want to stop my claim for universal credit but at the moment it is a big help so I hope people don’t think I’m just using the benefit system, I genuinely want to work.

Thanks