By our count, Kate Middleton is now five days past her rumored July 13 due date. So, what’s the royal baby hold up?

First, it’s important to note that it’s completely normal for babies to arrive one or two weeks after—or before—their ETAs, so royal watchers needn’t worry about Kate’s or the baby’s health yet. The average pregnancy lasts 40 weeks, but it’s not until 42 weeks that a pregnancy is really considered late, or “post-term,” according to the National Institutes of Health. So if she’s really five days late, the duchess’s pregnancy is still within a normal range.

There are, however, a few factors that make it more likely for a baby to come late. One that definitely applies to Kate is that first pregnancies are more likely to be overdue. In fact, research says that first babies are, on average, eight days late—so we may be waiting until Saturday or longer for the royal birth.

But here’s something even more fascinating: babies that come late are more likely to be male. Could this be a sign that the heir will be a boy? Studies suggest it’s more likely, but even the royal couple doesn’t know the gender of the baby, having opted for a delivery room surprise instead.

Other contributing factors to late deliveries are: overdue pregnancies running in the family, obesity, or the rare problem with the fetus or placenta. There’s also the fact that naming due dates isn’t an exact science—they’re just estimates. Obstetrician.