How Is Your Due Date Calculated?
Your estimated due date (EDD) can be worked out in two main ways:
• Last menstrual period (LMP): adding 280 days (40 weeks) from the first day of your last period. This assumes a 28-day cycle with ovulation on day 14, so it doesn’t apply perfectly to everyone.
• Early ultrasound (7–12 weeks): often more accurate, as it measures your baby’s size and development.
How Accurate Is a Due Date?
Here’s the truth: due dates are more of a guideline than a guarantee.
• Only about 4–5% of babies are born exactly on their due date.
• Most babies arrive sometime between 37 and 42 weeks, which is all considered normal.
Think of your due date as a guidepost it helps plan care, but babies don’t read calendars.
What Happens If You Go Overdue?
If you reach 41 weeks, your care provider may offer:
✔ A membrane sweep (also called a stretch and sweep) a simple procedure where your midwife or doctor sweeps a finger around the cervix to help release hormones that may trigger labour
✔ Extra monitoring for you and your baby
✔ Induction of labour, depending on your preferences and your provider’s advice
Can You Decline Induction?
100% Yes, you can. You always have the right to decline any intervention.
That said, after 42 weeks, the risk of your placenta working less efficiently does increase. Your care team will discuss the risks and benefits with you, so you can make an informed choice that feels right for you and your baby.
The Midwife’s Take
Due dates are a helpful planning tool, but they’re not a hard deadline. Your baby will come when they’re ready, and your care team is there to keep you safe and supported along the way.
Disclaimer
This blog is for educational purposes only and should not replace personalised medical advice. Always speak with your midwife or care provider if you have questions about your pregnancy or due date.
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