Babies born at 37 weeks should be classed as premature The difference is not enough to be noticeable between children, Dr Noble said, but was sufficient for mothers to "at least proceed with caution before electing to have an earlier term birth." Under current definitions, babies born at less than 37 weeks are classed as premature. Judy Aschner, a paediatrics professor at America's Vanderbilt University Medical Centre, said: "I don't want to panic mums whose babies come at 37 weeks, but those elective early deliveries really need to stop." The study has now been published journal Pediatrics. Last month, a study by King's College London found premature babies are twice as likely to suffer from severe mental conditions like depression and bipolar disorder in adulthood as those born on schedule. Babies born at 36 weeks gestation or earlier had double the chance of being admitted to hospital for mental disorders as those born on term, while those born at 32 weeks or earlier had three times the risk.