Hi, sorry to read about your mum. I am in a similar situation my mum got diagnosed just before christmas last year. She had surgery then 8 weeks of treatment. Unfortunately her tumour has progressed and they can't do anymore. It's a terrible disease but it seems to be very individual on how it progresses and at what speed.
having been through it all I would say just start enjoying your time together, making memories and being there. They re scan a fair bit later after treatment as the radiation takes a while after treatment to work (if that makes sense) it's going to be a tough road ahead and I feel for you with a young child and being pregnant. I too have young children. But keep positive and just live life together whilst you can. Try not to read too much on the internet, it can be a minefield of information which really can't give you any answers. Yes be prepared for what inevitably will come further down the line but just also keep a positive mindset that it won't be soon. 

I was diagnosed with GBM4 in July 2019. I had an operation and followed the chemo and radiotherapy route. My consultant gave the standard 12 to 15 months scenario, I am still here and never take each day for granted. It was upsetting for my wife and children but you cannot dwell on the negative and focus on the positive. Enjoy every day. Dr Google has a lot to answer for. Everyone is different so a timescale is just a measure that fluctuates. Keep positive. 

John