Your baby is a month old ! His brain is being formed from the neural tube that’s closing its front while its back part is slowly becoming the spinal cord as it is closing itself. Tiny buds will eventually form the arms and legs. At this stage, the embryo is entirely wrapped in the amniotic sac.

His little heart is beating and blood starts circulating in your baby's body. His digestive tube is developing and so is his mouth cavity. The placenta is developing rapidly and its expansion will continue until the twentieth week, at which point it will occupy about half of the uterus’ inner surface.

This week

Baby measures about 4 to 6 mm (from head to heel)
Baby weighs about 0.4 grams