A bodysuit (also called an onesie) snaps at the crotch and is designed as a base layer. It keeps the torso covered without riding up. 

A romper is a one-piece that covers both the torso and legs or shorts, making it a complete outfit on its own. Bodysuits are everyday layering essentials; rompers are more of a standalone look.

Always size by your baby’s current height and weight rather than age alone.

Our ClimaCuddle® bodysuits (both long-sleeve and short-sleeve) share the same sizing and run from 0–3 months (21–23"/53–58cm, 9–12lb/4–5kg) up to 12–18 months (31–33"/79–89cm, 25–27lb/11–12kg).

Our rompers go one size further, covering up to 18–24 months (33–35"/84–89cm, 27–30lb/12–14kg); so if your baby is on the bigger or older side, rompers give you a bit more runway. 

If your baby falls between two sizes, size up. For a full breakdown, visit our size guide.

For temperature regulation and moisture-wicking, our ClimaCuddle® Series uses a blend of merino wool and rayon made from bamboo: naturally thermoregulating, ultra-soft, and meets OEKO-TEX Standard 100.

Look for GOTS or OEKO-TEX certification to confirm the fabric is free from harmful chemicals.

Yes. Our bodysuits and rompers are made from Merino Wool and rayon made from bamboo, meeting OEKO-TEX Standard 100 requirements — no toxic dyes, no bleaching agents, nothing that could irritate delicate skin. 

Bodysuits feature snap closures, and rompers use a zipper; both are designed to stay smooth against skin, and tags are placed on the outside of the garment to keep them away from your baby’s skin entirely.

Absolutely. This is the recommended approach. A bodysuit or long-sleeve romper works as the base layer under a sleep sack, with the TOG rating of the sleep sack determining how much extra warmth your baby needs. 

See our sleep sack layer guide for exact combinations by room temperature.

Yes. All Kaiya Baby rompers feature a zipper closure, so you can change a diaper quickly without fully undressing your baby, making nighttime changes much less disruptive.

Machine wash on a gentle cycle in cold water using a fragrance-free, dye-free detergent. 

Pre-treat stains right away, such as formula and breast milk. Air-dry when possible to preserve elasticity and print quality. For full care instructions, see our wash care guide.

Plan for 6–8 bodysuits across multiple sizes (newborn, 0–3M, 3–6M) since you’ll go through several a day. 

For rompers, 3–5 is a good starting point as they’re more of a complete outfit. Buying too many in newborn size is a common mistake since babies outgrow it within weeks. 

See our full baby essentials clothing bundle to get started.

Yes, we ship all over the world. Shipping costs will apply, and will be added at checkout. We run discounts and promotions all year, so stay tuned for exclusive deals.

Free shipping over $89

Expected Delivery for US standard shipping is 5-12 Business days.

Expected Delivery for US VIP Shipping is 4-10 Business days.

Delivery details will be provided in your confirmation email.

You can contact us through our contact page! We will be happy to assist you.