The huge changes that occur during pregnancy have been felt by people for millennia, but it's only in recent years that we've had data to back those feelings up. India Rakusen talks to Herman Potzner about just how energetically taxing pregnancy is, and to Elseline Hoeksma about the changes in the maternal brain. Presented by India Rakusen. Producer: Ellie Sans. Series Producer: Ellie Sans. Executive Producer: Suzy Grant. Commissioning Editor: Rhian Roberts Original music composed and performed by The Big Moon. Mix and Mastering by Olga Reed. A Listen production for Radio 4 and BBC Sounds.