I made these in a 62 for a baby just a little taller than that, and they still fit fine (length wise) for several months. I like that the design includes long cuffs at the ankles, so they can be folded up or left down according to how tall your baby is getting!

A totally simple pattern to make - I left out the clear elastic for gathering the leg openings, just used gathering stitches. They snapped, of course, the first time I put the pants on the baby, but that was OK, because the gathering was already done and the sewing of the cuffs to the legs held everything in the right place.

With the pinafore/dress from the same issue (design #1):


And on the baby, about 65cm, almost four months old:


I agree with the previous opinion that these are roomy enough to make with a woven fabric, as long as your cuffs are still cut from a knit. (My daughter was in a cloth diaper there - tons of butt room!)