Mom out there diaper size advise

Zorayah • I'm a FTM engaged due Jan 8th,2016 with a little girl 💜❤️💗👶🏼
I'm 18 weeks and 6 days I know it's kinda early but I was wondering how long your little one/s stayed in sizes I want to stock up but curious as to the sizes your baby's stayed in newborn? Size1? Size2? Size3? Please and thank you ladies so much