What is the 4th trimester?

Available for over a year

We all know that in a forty week pregnancy there are three trimesters but have you hear of the fourth? Why is it important to distinguish the three months after you've given birth? How come so few of us have heard about it and what do health professionals and pregnant women need to know about it? Jenni Murray asks Hannah Horne, a perinatal mental health midwife at Wirral University Teaching Hospital, and Amy Ransom the author of the New Mum’s Notebook.