The due date myth!

One of the first things we often do when we find out we’re pregnant is that mad calculation to figure out that magical day when we will meet the new love of our lives – the due date! I am not a big fan of this one though, as I believe it causes a lot of undue stress and worry, and I think we could do this a bit better. To illustrate my point, I was once working as a midwife in an emergency department when a woman turned up because it was her due date and nothing was happening. She was concerned, because nothing was happening! I felt awful for her, because her care must have been very substandard to go 40 weeks without learning how things go at the end of pregnancy.

The due date is historically calculated 9 months and 7 days from the first day of the last period. Here we run into the first issue: what if you’re not sure when your period was? What if you had spotting leading up to the period – when do you count the first day? What if you have a particular type of contraception or medical condition where you don’t get regular periods? What if you haven’t had a period since your last baby? Thankfully, we now have some really precise technology in ultrasounds, which can be really accurate in measuring a tiny baby in utero and therefore calculating how old it is, and when we can expect it to be born. But here lies our next problem: actually, it’s really unlikely that a baby will be born on the exact due date – only about 4%, to be exact[1]! Statistically, if you’re a first time mum, pregnancies tend to go a little longer and about half of first time mums are still pregnant at 40 weeks and 5 days[2]! For mums who have had babies before, about half will still be pregnant at 40 weeks and 3 days – showing us the natural shorter pregnancy length that often occurs in subsequent pregnancies[2].

Getting confused? When is that baby actually going to arrive?! Well, the graph below is data from the Victorian state government's publication on births in Victoria in 2016. Data from New South Wales shows similar rates, just to give you an idea of very minimal variance in the statistics. 

So it’s obvious that most babies are born between 37 and 41 weeks of pregnancy. In fact, less than 1 in 10 babies will not be born in this time period. Personally, I think we would save ourselves the stress and worry of trying to guess when our baby will arrive by working off a due “month”, or the range of dates that is 37-41 weeks of pregnancy. For example, if your due date is calculated to be March 26th, your due “month” would be March 5th to April 2nd. Another alternative might be to give mums the last date in this range, and advise that induction of labour would be recommended following this date – in other words, if baby hasn’t arrived by date x, the next day would be the date of induction of labour. Some countries already operate this way!

For anyone that has been pregnant before, it can often be exhausting and upsetting to field the constant questions, calls and texts that arrive around the due date, from well-meaning friends and family, especially if you know and understand that baby might arrive after the due date, and you’re trying to be calm and patient. Imagine how frustrating to receive relentless questioning on “has baby arrived yet?”! This is not going to relax you and help you go in to labour! One tip I have is to tell your friends and family that ultimate last date before potential induction, if you know it. Or tell them a date that is actually 2 weeks after your due date. This way, you mightn’t be hassled as much, and if baby arrives early then you’ll have a wonderful time surprising everyone! Another bonus tip - click here to see my secret weapon for bringing on labour!

Questions? Confused? Contact me or comment below! Mamas, when did your baby/babies arrive? 

Want more?

Click below to read related topics, like Caitie's experience when she went past her due date, my top tips on how to start labour naturally, or how acupuncture might help you! 

[1] Jukic, A.M.; Baird, D.D.; Weinberg, C.R.; McConnaughey, D.R.; & Wilcox, A.J. (2013). Length of human pregnancy and contributors to its natural variation. Human Reproduction 28(10): 2848 – 2855




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