Your answer is true. But the way this question is worded it could be read as a baby born before is premature so therefore a baby born after the due date is post mature. With no real detail to this question it can make it hard to understand what you are trying to get across.
A due date is just an estimate of when your baby will arrive. Since normal gestation is anywhere from 37 to 42 weeks, a baby is not truly post-dates or post-mature until after 42 completed weeks. Although the risk of meconium in the amniotic fluid goes up after 41 weeks, the vast majority of babies born between 41 and 42 weeks are healthy. In fact, the average length of pregnancy for first-time moms is 41.2 weeks!