Mothers’ and babies’ brains can work together as a ‘mega-network’ by synchronising brain waves when they interact. The level of connectivity of the brain waves varies according to the mum’s emotional state: when mothers express more positive emotions their brain becomes much more strongly connected with their baby’s brain. This may help the baby to learn and its brain to develop.

https://www.sciencedaily.com/releases/2019/12/191217105210.htm