arguing after having a baby?

Sounds pretty normal after having a baby. A baby is a big change plus your hormones are all over the place from birth. It’ll get better with time especially if you guys make sure to make some time for yourselves too

It's probably you're both overwhelmed with this big change of having a baby. You as a mama have been through a lot and hormones are all over the place, there's also something called postpartum blues. Both of your lives have just significantly changed and are now faced with a big responsibility. All these things will make anybody on edge and can bring out versions of you that you are not familiar with. If you guys are best friends and have been good partners for years, then you should talk things over, like the things that irritate, hurt, annoy each other. Give each other grace (like a lot!). It's hard to be pregnant and to deliver a baby, also from a man's perspective even though they didn't go through the physical, hormonal roller coaster, they also go through mental, emotional stress and anxiety, heck you're bringing a human being in this crazy world. When you feel like you're starting to get snarky, breathe and try to describe your feelings or whatever is wrong and have a conversation first.

This is totally normal. You've just gone (and are still going) through a massive change in your lives in a very short space of time. For one thing, each of you is no longer their partner's sole reason for living. You're also likely to mess up a lot because this is all new. Plus you're probably both sleep-deprived. Try to have patience and forgive each other. A phrase I used a lot is "we're both just trying our best". It will get easier, you just need time to adjust to the new normal.