Hi Tegan

There is no way of accurately predicting your EDD. Even if you only have sex once a year it is still not possible to say what your exact EDD will be. For example did the egg and the sperm meet on the day you had sex or was it 3 days later. Sperm can live for up to 5 days. Your EDD is only a guide. As others have said, most babies do not arrive on the due date.