Knitters and parents of young babies - I need help!

[LewisFan]

Knitters - do I need to start again because the newborn cardigan i made came out an inch narrower than the pattern (that had mistakes in it so may not be particulalrly reliable)?

Also, can you undo a cast off row so I can reuse the ball of wool?

Parents of babies - how wide are 0-3m cardigans from armpit to armpit?

Botheration.

Did you do a swatch beforehand to gauge your tension? I assume you’re using the right wool and needles?

All my DD’s cardigan’s vary in width!

Yes, you can undo that last row too.

Honestly, looking at the variation in the cardigans I have, I don’t think one inch will make much difference!

You can unravel the cast off row by undoing the knot you will have made to secure the last stitch when you took it off your needle, and the row will just undo as you pull the wool.
Baby knitting patterns start at 19.5inches across so that's probably newborn size I'd guess! They're made to be a couple of inches bigger than the actual baby so you might get away with your cardigan being a bit smaller!

My swatch was ok... I'm so peed off!

Fortunately I have time and didn't knot it yet as I had a feeling it was too skinny

Before I had my first baby I always made 0-3 month size cardigans that were sized to fit a 16" chest.

When DD1 was born a friend of my DM's had knitted a cardigan sized as "large preemie" with a 14" chest. This was the only cardigan that fitted her perfectly as a newborn (up to about a month old) and now I always make at least one cardigan in this size when I'm knitting for a newborn.

TL:DR - you've probably sized it perfectly.

Ooh maybe I'll leave it and just do another one bigger so she can carry on using it when the first one is too small within a few weeks it's 8" across the first from armpit to armpit, so 16 around...

Across the chest I meant

Sounds spot on for a newborn.

WRT a bigger sized cardigan just be aware of the seasons. I come from a family of knitters and I knit myself. My 2 DDs were spring babies and I had 20+ hand knitted cardigans and hats for each of them. They hardly wore the bigger sizes as it soon became too warm for a cardigan. I'd hate for all your hard work to sit in a drawer unused because we have another summer like last year.