Week 18: your baby is the size of a pygmy marmoset

Your fetus is now the size of a pygmy marmoset, the smallest monkey in the world, with a body of about 12 to 15 cm and a weight of about 100 grams, roughly a stick of butter. It lives in the rainforest canopy of the western Amazon.

It is a gum specialist: it gnaws tiny holes in tree bark with specialized teeth and laps up the sap that oozes out, spending its whole life among a handful of favourite trees.

It can leap up to five metres between branches, swivel its head roughly 180 degrees to watch for hawks, and chatter in high calls that partly rise above the range of human hearing.

Meanwhile, inside you

Your fetus this week may be old enough for you to feel their first flutters of movement, sometimes called quickening. Their ears have also moved into position and can begin to pick up sound.