is it bad to ..

So my baby is currently 3 weeks and a day old. and I've been going out with her to her dads so he can see her. They've been picking us up. And my mom is mad because she says it's bad to take her out the first 40 days? Is this true? It's getting me a little annoyed because she gets upset over my personal decisions and it's not like I'm doing my baby any harm or something.