Bun in the oven

This expression for pregnancy in this particular wording format is thought to date from only the mid-20th century, where it is cited in Nicholas Montserrat’s The Cruel Sea (1951) but there is evidence that the use of the baking metaphor to describe pregnancy is much older. There are many instances in literature from at least the early 17th century onwards that describe pregnant women as having a cake or a bun in their wombs, bellies or ovens. The metaphor seems to have occurred to so many different writers down the years that it is very difficult to pinpoint specific coinage or origin.