I often tell my clients, “forget about your estimated due date. Think about it as your estimated due month” instead! When the obstetrician tells us that magic date, it’s natural to focus in on it like an absolute target and the closer we get to this magic day, the more anxiety we experience. Not to mention the endless reminders from family and friends enquiring as to “have you had the baby yet?” Well, duh, I think you would have heard! Personally, I like this one which many a friend has posted on Facebook.

Calendars can be comforting – we like to flick through our diaries or our wall calendars. They help us move through the paces of everyday life and plan ahead for important events. While circling your due date might help you to make it all seem more real, or help you plan for the birth, the truth of the matter is, you can never predict exactly when your baby will be born.

First of all, let’s look at how your due date is calculated in the first place. Pregnancy (or gestation) lasts an average of 280 days or forty weeks after the first day of your last period. Although conception occurs within 12-24 hours of ovulation, it’s difficult to know exactly when ovulation occurred. For many women, ovulation happens about two weeks after the first day of their last period, but it can occur earlier or later in the menstrual cycle. This uncertainty makes it difficult to know exactly when a woman becomes pregnant, especially is she has sexual intercourse frequently and conception can’t be traced to a particular day.

Therefore, doctors or midwives will calculate the due date by using this simple formula: subtract three months from the date of the first day of your last period (a date you can confirm and which many women are likely to remember or keep a record of), then add seven days. For example, let’s say the first day of your last period was March 1. Three months before that is December 1. Add 7 days gives you a due date of December 8. Most obstetricians will also want to use ultrasound in early pregnancy to help estimate the due date.

Bear in mind though that a normal gestation is anywhere from 38 – 42 weeks and the estimated due date is literally the date in the middle of that period (i.e. 40 weeks). In reality, only about 5% of women give birth on their actual due date and most women give birth within 10 days of their due date on either side.

Imagine you’re making some microwave popcorn. Most of the kernels pop around the same time, but there are still lots that pop a bit early and lots that pop a bit later. All the popped kernels are perfect – but each needs a slightly different length of time to be fully cooked. The same is true for babies!
Many obstetricians are keen to induce labour at the end of 41 weeks, but in and of itself, this is not a reason backed by medical evidence to induce labour. There must be a clear medical benefit for either mum or baby (or both) to end the pregnancy, rather than continue with it.

While you might be restless and impatient to finally meet your baby, don’t let this be a reason to agree to an unnecessary induction. All pregnancies eventually end! Only your baby knows when he or she is ready to be born. Your baby’s chemistry communicates with yours to declare that all systems are go, and labour should begin.

Calculate your due date with our due date calculator here

Tanya Strusberg is a Lamaze Certified Childbirth Educator (LCCE) and teaches prenatal education to pregnant women and their partners in Melbourne.
She and her husband Doron have two beautiful children, Liev and Amalia.

To learn more visit www.birthwellbirthright.com

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Disclaimer: The information contained in this column is of a general nature only and does not constitute formal medical advice. Any specific medical problem should be referred directly to a qualified health professional.