As the world’s population continues to rise, the numbers of children born per woman is still falling. Worldwide there’s now around 2.49 live births per woman, not far above replacement rate. Many couples are choosing to have smaller families and contraception is helping. But meanwhile, infertility in both men and women, in rich and poorer countries, is increasing. Fifty million couples worldwide cannot have children without medical help. So, what is going on? Celia Hatton and a panel of expert guests discuss why so many men and women are struggling to have children. Are they simply leaving it too late or are other factors, such as diet or pollution, having an effect? (Photo: Couple in consultation with a doctor. Credit: BSIP/UIG/Getty Images)