Yes, the smallest size available is 0-6 months, designed to fit infants up to 6 months old. For ages 6 months to 18 months, we suggest considering size 1. However, since every baby is unique, we recommend referring to the sizing chart provided on each product page to ensure the best fit.

If you are not very good at understanding sizing, please check these extended readings:
Baby clothes sizing;
Understand the infant clothing size chart.