I wanted to keep alive the thick - thin character of the yarn I spun so I decided for a simple yet stretchy pattern: the English rib stitch also called the fisherman's rib. Here's a video tutorial explaining how to knit this very simple stitch.
For this vest I cast on 34 stitches on size 4 needle. I worked my way up 14 cm. At this point I worked one shoulder by keeping on a separate needle only 10 stitches and knitting those 10 stitches for 6 cm. I then continued the row I left undone by casting of 14 stitches in order to make the neckline. The last 10 stitches I knitted for 6 cm in order to complete the other shoulder. When I was done I joined the two shoulder pieces by adding 14 stitches between them, thus closing the neck hole. I continued knitting the back of the vest (20 cm).
To finish the vest, I joined the sides and for a neater look I crocheted an edge around the arm holes and neck hole (single crochet stitch). And that's it - vest is done. Now I need to wash and block it and wait for the boy to be born... pff... still 4 months to go.