What size should I buy ladies🤔This has me going crazy.

Okay so our baby boy 💙💙is due 10/25(plz let me go full term) lol, I live in the New York area so October especially late October in general is tricky in weather. I don't know if a snow suit is way too hot to take him home, I was thinking about a Sherpa or pram from carters. But what size ladies????What size do I buy newborn or 3months these are the two options from carters. My growth scan showed average weight so far, my GYN said as of now our baby is 60 percentile he feels right on target of weight. I'm looking to order this soon but what if I get newborn size and it doesn't fit , or what if I get 3months and he's swimming in it. Ladies help me out lol. 😩😩😩😩😩😉