Claudia Hammond investigates an often hidden condition: perinatal obsessive compulsive disorder which can affect pregnant women or new mothers. Women with perinatal OCD can have obsessive thoughts about contamination and cleanliness or a less well known aspect of the condition which is compulsive thoughts and intense fear of seriously harming their children. They go to extreme measures to prevent themselves doing any harm, although they never would. Women can be treated successfully with cognitive behavioural therapy. Claudia talks to Fiona Challacombe, clinical psychologist at the Institute of Psychiatry about the condition and its treatment. Also in the programme, the brains cells that have been described by one neuroscientist as underpinning civilisation - have they been overhyped? Claudia talks to mirror neurons expert, Cecelia Heyes from Oxford University. And does a baby pick up anxiety more from its mother or father? Claudia talks to researcher, Eline Moller from Amsterdam University.