By 16 weeks your baby will be around 12cm (5 inches) from head to bottom and weigh around 130g (4½ oz) - about the same weight as an apple or a pear.
It's active in there - your baby is experimenting with lots of different movements, including thumb sucking and grasping the umbilical cord!
Fingernails and toenails are small but perfectly formed. If you could take a peek inside, your baby would look like a perfect little human, but very thin and reddish; there’s no fat layer yet, so the blood vessels show through the skin. Never fear – the filling-out bit comes next!