My boy is formula feed and 3 weeks old and is going every 48 hours. I was really concerned as often he is really trying to poop and nothing happens. I asked the midwife and health visitor and both said is normal at this stage as they are starting to use muscles required so can take some time to establish what they have to do. They also said it would only be a concern if they didn’t go after 5 days!!!
Formula fed, she poops once, max twice a day. Midwife said it’s normal
My little girl is 3 weeks old and gets formula fed with a couple of ounces of expressed breast milk a day too. She only poops every 1 1/2 to 2 days. She’s not straining or showing any signs of discomfort tho so I’m not concerned.