It may just look like a pretty pendant, but the Blooming Lovely Simple Satin Mexican Bola Pendant (£23) holds a special secret. It features a bola (also known as a harmony ball or angel caller) which has a gentle chime. When worn low against the bump, it makes a sound whenever mum moves that becomes familiar to the baby, the aim being that it can continue to be used to soothe the baby once he or she is born.