Finished baby ribbed hat measures:
3-month old = 14 inch circumference by 6 inches long with WW yarn
Newborn = 13″ cir by 5-1/2″ long with WW yarn
Small newborn = 12″ cir by 4.75″ long with DK yarn

If using DK yarn, crochet one addl round before adding 3 rows of ribbing to achieve 4.75 inch long hat.

Hooks:
H (5 mm) US sized crochet hook for 3-month baby
G (4 mm or 4.25) US sized crochet hook for newborn

Materials: 1 ounce Worsted Medium Weight or Aran Yarn,
DK Yarn or light

Gauge: WW yarn; 3 rows =1”, 4.25 sts = 1”
DK yarn; 4 rows = 1”, 4 sts = 1”