Everything you've ever wanted to know about your due date!

“When are you due?” is usually the first question asked once people know you are pregnant, usually followed shortly after by, “are you having a boy or a girl?”.

How can you know exactly when your baby is going to be here?

We are a society obsessed with your due date!

Anyone who has ever been pregnant and gone past their due date has heard the question: “Have you had your baby yet?”

This post will cover everything you need to know about your due date including some interesting facts about when your baby is actually going to be born!

Also, what to say to all those nosy people who will be calling you once your due date has passed.

Last Menstrual Period

The first day of your last period is used to calculate your due date. You might hear the abbreviations EDD (estimated due date) or EDC (expected date of confinement) from your health care providers.

The most common period cycle length for women is 28 days, although many women have shorter periods and many have longer. In addition, some may have irregular periods.

Your due date is calculated to be 280 days (this is exactly 40 weeks) after your last period. This is the average time most women give birth, but by no means is it a crystal ball determining the day your baby will be here!

These calculations are based on a 28-day period cycle. If your cycles are shorter or longer, your calculated due date may be off by quite a bit, and it’s hard to know how much.

That’s because, with irregular, short or longer periods, it is very difficult to know exactly when you ovulated, which is basically when your baby was created!

Some women don’t keep track of their periods, so dating according to this method wouldn’t really work for them.

DIY: Calculate Your Due Date!

If you do know the first day of your last period you can calculate your estimated due date by adding 280 days to the first day of your last period. Another way to do it is to subtract 3 months and then add 7 days and one calendar year.

For example, if the first day of your last period was March 19th, 2019, then you count back 3 calendar months, which would bring you to December 19th, 2018 and then add 7 days and 1 year which would bring you to December 26th, 2019.

That’s your due date!

If that’s too much math for you, there are a lot of due date calculators online that will help you out.

I really like this one: Due Date Calculator.

It’s neat because it will give you all kinds of information on your pregnancy, including what seasons you’ll go through in each trimester.

Find out all there is to know about your due date from an L&D nurse. Find out when your baby will be here!

First Trimester Ultrasound

Another way to estimate when your baby will be born is by measuring the fetus in the first trimester by ultrasound. The length of the fetus’s body is measured and compared to the standard fetus size at a certain gestation. Obviously, if your baby is small or big, the ultrasound might not be as accurate either.

Ultrasounds after the first trimester are much more inaccurate in calculating your due date so don’t rely on them.

The first trimester ultrasound is a good way to find out your due date!

Your Baby Might Have Other Plans

With all that said, don’t bet on your baby coming on the actual date you are given. Research has shown that only 5% of babies come on the actual due date.

Say what?

I know! When you see that, it’s obvious that your due date is really just a GUESS date.

We really have no idea when your little one will make his or her appearance.

It’s really all just guesswork.

 What are the Risks of Being Overdue?

There are a lot of scary stories out there about being overdue. Being past your due date per se isn’t dangerous, but being more than two weeks overdue can be. This is called being post-term.

Usually, if you’re more than one week overdue your doctor or midwife will want to deliver your baby to decrease the risks of anything bad happening.

But what exactly are those risks?

Once past your due date, the placenta can start to deteriorate. The placenta is your baby’s life support in the womb. With time, it might start to develop calcification, which decreases its function and can affect your baby. Usually, calcifications can be seen on ultrasound when this happens. It is a normal process, but in extreme cases, it can be fatal for your baby.

Your baby will keep growing, which might cause issues during your delivery. The longer you go past your due date the more your baby will grow.

A bigger baby might cause you to have an emergency c-section or shoulder dystocia. Which are things you’d probably like to avoid during your delivery!

Babytalk has an article about c-sections to prepare you ahead of time! What to Expect When You’re Getting a Cesarean Section

There could be a decrease in the amniotic fluid. Although it is normal for fluids to drop as your pregnancy progresses, when there is too little amniotic fluid there is a risk that the umbilical cord can get compressed which can be very dangerous for the baby.

Lastly, your baby might poop in the amniotic fluid which is not normal. Once this has happened there is a risk of meconium aspiration during delivery, which is a very serious condition where the poop causes an infection in your baby’s lungs.

Monitoring Once You’re Past Your Due Date

Even though the science of your due date isn’t that accurate, your health care provider is going to want to monitor you very closely once your due date comes and goes. Most likely they will send you for a non-stress test, which is a 20-30 min test where your baby’s heart rate is monitored and checked to see that it is showing signs of being active and healthy.

You might also have to go for more frequent ultrasounds to check the baby’s growth and placenta. Those ultrasounds will also measure that amniotic fluid volume and baby’s breathing. This is called a biophysical profile.

If there are any concerning signs, your health care provider might recommend an induction to start labour.

Induce your own labour once you are overdue! Tips and tricks from Babytalk: How to Naturally Induce Labour Yourself: Four Incredible Tricks

What Starts Labour?

This is not completely known, but it is most likely a combination of things.

There is a change in your hormones right before labour and the fetus sends signals to your body that their lungs are mature and they are ready to come out. This is why it’s not good to induce labour before the baby is ready. It’s hard to evaluate exactly when the lungs are mature enough for life on the outside.

For whatever reason, some women don’t go into labour on their own before 41-42 weeks. If this happens to you, you might have to be induced. The American College of Obstetricians and Gynaecologists believe that the safest time to induce labour is at around 41 weeks as long as everything else is going smooth with the pregnancy.

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Inductions for Post Dates

If your baby isn’t here once you have passed your due date and you are not showing any signs of labour, your health care provider will probably want to induce you. Talk to your provider and come up with a plan that works for you!

If you really don’t want to be induced, he or she might have some ways to help you go into labour on your own.

The deciding factor on how you will be induced depends on whether or not you are dilated and if your cervix is favourable.

Want to know more about inductions? Check out this article right here on Babytalk! Everything You Ever Wanted to Know About Inductions

If your pregnancy is otherwise normal, you will probably be able to wait until week 41 to be induced. But that’s up to your health care team.

While you wait for your baby to get here, turn off your phone and ignore all the comments. As it is with parenting, everybody will have an opinion on how to get your baby to come out.

If you do talk to people about your due date, how about giving them a due date window instead of one set day? Say for example, “my baby is due at the end of December” and don’t give them the exact date. That way they won’t be bugging you once that date has come and gone.

Your baby will get here when he or she is good and ready!

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About the Author

Hanna is passionate nurse and mama of four babies. Parenthood can be hard, but you don't have to do it alone. Hanna is here for you from pregnancy, to birth and beyond!

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