Don't be surprised if your due date passes you by. This is common, especially if this is your first baby. 
Only 5% of babies are born on their due date, notes the <a href="http://www.netreturns.biz/healthinfo/bouncelink.aspx?shortcut=acog" target="_blank">American College of Obstetricians and Gynecologists</a>. 
Your due date is usually 40 weeks after the first day of your last period. But it's normal for a pregnancy to last as long as 42 weeks. After that, a pregnancy is post-term, or postdate. 
Longer pregnancies can cause problems for women or their babies. So your healthcare provider may want to do some tests if your pregnancy lasts longer than 40&nbsp;weeks. 
Those tests can check on your baby's health. They'll also make sure your original due date was correct. 
The original due date could be off if you didn't know when your last period started. Or you may not have ovulated at the expected time. 
An accurate due date may be harder to figure out if you became pregnant soon after going off birth control pills. 
Your healthcare provider may recommend other tests to make sure your baby is still in good health. They'll also check that baby is not getting too big. If baby gets too large, it can cause problems during delivery. 
Your provider will look at all the test results. Then you may need to wait and do the tests again. Or the doctor may suggest trying to start, or induce, your labor. This may include medicine or other methods. 
Reviewed 2/22/2024

Pregnancy: When your baby is late 

Many pregnancies last longer than expected. In most cases it's nothing to worry about.