We get this question a lot, and the honest answer is that muslin clothes don't run big or small the way some fabrics do. They run true to age. Our sizes cover roughly newborn up to 4 years, and because every piece is pre-washed before it leaves us, it arrives already at its finished size. That means no surprise the first time you wash it: it won't pull in and turn a 12 month outfit into something that only fits a 6 month old.
The open, loose weave of muslin gives the fabric a bit of natural stretch and drape that a tighter cotton weave doesn't have. That's why a piece can feel roomier than the size on the label suggests, especially around the arms and middle. It's just how the weave behaves, not a fit problem. Our clothes are double layer muslin cotton with flat seams, so there's nothing pressing or rubbing as your baby moves around in them.
For care, wash cold on a gentle cycle and tumble dry low or hang to dry. Skip fabric softener and high heat, both work against the weave over time. Muslin also creases easily, that's normal for this fabric, and it softens more with every wash. If a piece doesn't fit the way you expected, we ship worldwide with tracked delivery and accept unworn returns within 30 days, so sizing is never a real risk. We're Vanessa and Bob, we design these pieces ourselves in Bali and size them for real kids, not just a chart.