Mums help me please

Pip • Pregnant with a little boy • c-section is booked for 4th July 2016 at 8am ✨
I'm buying baby clothes. It says newborn is 7.5lb. Do I get some tiny baby vests as well just in case at 5lb or is that extremely premature? Also 1 month is 10lb, shall I get more 1 month things then newborn? I don't know these things because it's my first..