Yarn: Something that gives 10 cm = 21/22x34 stitches. I used Sajama Alpaca and needle 3 mm.
If you don't like to knit swatches, start with an arm, it is far less to frog if it turns out wrong.
Yarn in 3 colours, I used around 70 g plum, 25 g nature white and 40 g nature black. Needles size 3, dpn's for arms and a circular for the yoke 2 cute buttons for the shoulder, a needle to weave in ends, attach the arms to the yoke, and to sew on the buttons.
CO: 120 sts and knit around.
The cable rib is knitted like this:
1: P2, K2 repeat
2: P2, K2, repeat
3: P2, slip one st on a needle behind the work, K1, K the slipped st. repeat (an easier way to knit this cable is to leave both sts on the needle, but knit st number 2 first without slipping the first st off, and then knit st number one, and slip both sts off together)
4: P2, K2 repeat
Knit until rib is 3,5 cm
Yoke: Continue knitting around with plum (or your own main colour) until work is total of 18 cm
Now part front and back and knit across 60 sts, and purl back 60 sts in black and white stripes.
Each stripe is K1 row, P1 row.
Front: After 10 cm you round the neck like this (while continuing the stripes):
Left shoulder (the right side facing you)
Knit 20, turn, P2tog, purl all sts, turn
Knit all, turn P2tog, purl all, turn
Knit all, turn, P2tog, purl all, leave sts on a needle or stitch holder.
Count 20 sts for the neck, leve these also on a needle
Right shoulder (or left facing you)
K2tog, K all, turn, Purl all, turn
K2tog, K all, turn, Purl all, turn
K2tog, K all, turn, Purl all
Knit stripes until you have the same amount of stripes as the front. It should measure 30 cm total.
Leave all sts on the needle. Put away and knit arms.
Arms: CO 32 sts on dpn's and knit cable rib around for 3,5 cm as described.
After rib, increase 2 st each 4th round under the arm. I increase on each side of 2 sts.
Knit Plum (main colour) for a total of 9 cm with the rib and change for stripes. Knit stripes (remember to increase) until the whole arm is 17 cm and cast off loosely. The arm might look very short, but babies are strangely proportioned.
In case you forgot; make one more arm, just like this one.
Collar and finishing:
Now start to attach the different parts together: I left the stitches on the shoulders to avoid seams there, so use grafting (sewn or knitted) to put together the right side shoulder (left facing you).
Now knit all stitches from the front side of the left shoulder with black yarn, pick up 6 sts where you rounded the front neck, knit all the 20 front stitches, pick up 6 sts on the other side of the rounded neck, and knit all the back stitches. Now knit and turn across all these stitches K2, P2 4 rows
Make buttonholes the next row like this: Work K2,P2 according to your work 4 sts, cast off 2 sts, K&P 4 sts cast off 2 sts, continue working K2/P2 across work. Turn. Work knit 2 and purl 2 as usual until you get to the button holes. Work 2 sts in the end st and connect the hole to the work again. K/P 4 and repeat with the other button hole. K/P last 4 sts. Turn and work 3 more rows ending with the front facing you. Cast off loosely.
Block all parts before joining them. If the yarn tolerates it, use a steam iron.
Sew the left shoulder collar short ends (where the arm starts) together, laying flat on top of each other. Sew on the buttons.
Join the arms and sew on. I like to start on the top of the arm working my way down, in case I have to hide a few rows of sin (if it doesn't fit properly), better to hide it under the arm than on visible places.
Weave in ends, and you have a baby pullover!