8 weeks old

Mercy • I'm 27 years old and me and my husband are expecting our 2nd baby in March. Our daughter is almost 2 and we are excited to be giving her a sibling!
My daughter is eight weeks old tomorrow and only poops about once today. She hasn't pooped since the night before last (36 hours ago) and I'm a little concerned. How often should she be pooping at this point? She is mostly breast-fed but has about an ounce of formula in each bottle to help with her acid reflex.