Almost one in five pregnant women in the UK is clinically obese. Obesity during pregnancy puts both mother and baby at greater risk of almost every medical complication in the book. One Born: Plus Size Mums follows three morbidly obese pregnant mothers as they, and the professionals who care for them, do all they can to bring their children safely into the world. But not all runs smoothly. The film follows super-morbidly obese, Lucy, and husband, Barry, who have been trying for seven years to have children.