80% of women deliver between 37 and 40 weeks, but that's a big window when you've waited almost 10 months (not 9!). Here's what you need to know about when baby might show:
1. There's no foolproof predictor: Due date calculations use a 28-day menstrual cycle, bu all women differ. Even sonograms can't pinpoint one delivery day.
2. Due dates are deceptive: Surprise: Just 5% of women give birth on their due dates! So odds are, you won't.
3. Baby may arrive too soon: About 11% of moms-to-be deliver prematurely—defined as delivery before 37 weeks. Having had a preterm delivery in the past increases your changes of it happening again.
4. ...But too late can be risky, as well: After 42 weeks, the risk for placenta deterioration rises, and amniontic-fluid levels drop. Baby's infection risk increases too. Talk to your ob/gyn about how long you can expect to go before getting induced.
5. It may be genetic: If this is your first pregnancy, you're likely to deliver early if your mother did.
6. You may be in it for the long haul: Caucasian moms tend to have the longest pregnancies, and so do women under 30. And boy babies are more likely to be born later than girls.
7. You'll be sick of people asking, "When are you due?": And if your due date comes and goes with no baby? Really, just stop checking social media.