I Have Some Very Conservative Investments, Mostly Mutual Funds. What Will Happen To Them In A Deep Recession?

I have some mutual funds which are made up of very conservative investments – nothing too risky. Over the past few decades this fund has done nothing but grow slowly. Sometimes it goes down a bit, sometimes it spikes a bit, but overall it shows a pattern of growth, which is great.
What will happen to these investments if we go into a bad recession?
Will they decrease in value a lot?
Should I try and head this off by changing my portfolio? Or just ride it out?
Thanks!