Up to you two. 5 girls can be lots of fun too--or 4 girls and 1 boy, if you're lucky. There's no guarantee that you'll have a son, however. Your chances of having a son are not increased by the fact that you already have 4 daughters. The chance of having a boy appears to decline with the mother's age, the father's age and the number of children the family already has. These effects are very small, however.