Find out how to calculate your due date, plus learn when most babies are born and what to do if baby’s late.
Maybe you’re already a week past your due date and thinking about natural induction methods. Or maybe you’re just starting your pregnancy journey, and you’re wondering when you’ll meet your baby face to face. There’s always that burning question: When will my baby be born?
While we can’t zero in on a precise answer—sorry!—we can learn a little bit more about due dates and when most babies are born, statistically speaking.
In this article, we’ll explore:
How Do You Calculate Your Due Date?
Just like trying to figure out how many weeks pregnant you are, there is some math involved in figuring out your due date (aka the answer to the question when will my baby be born), and there are several ways to do that math.
How to calculate your due date with Naegele’s Rule (last menstrual period)
- Start with your LMP (last menstrual period). Let’s say it’s July 1, 2018.
- Go backwards three months. For the sake of our example, that would be April 1, 2018.
- Adjust the year (add one year) and add 7 days. That would make our example due date April 8, 2019.
Why does this work? This method works with the understanding that pregnancy is 280 days from the LMP, but—and there’s a big but—it really only works well for a perfect 28-day cycle. It does not take into account longer or short cycles or cycles with delayed ovulation. (source)
How to calculate your due date from ovulation
From ovulation, a typical pregnancy will last 268 days, or 38 weeks and two days, according to research from an article published in Human Reproduction.
But you don’t have to be a math whiz to figure out your due date—we’ve done the math for you.
How Many Babies Are Born on Their Due Dates?
A due date isn’t like a magical expiration date that answers the question when will my baby be born. Your due date is—at best—an estimate. Studies show that healthy, normal pregnancies can vary by as much as five weeks, or 37 days! (source, source)
With this in mind, it’s probably no surprise that:
- Only 4 percent of babies are born on their due dates.
- And 70 percent of babies are born within 10+/- days of their due date. (source)
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When Will My Baby Be Born?
So if only 4 percent of babies arrive on their EDD, it begs the question: When will my baby be born?
According to the Eunice Kennedy Shriver National Institute of Child Health and Development, most women go into labor between week 37 and week 42. (source) According to a survey conducted by the National Survey of Family Growth, about 60 percent of babies are born during the 39th week. (source, source)
Even those babies born during the 39th week haven’t hit their due date yet, this is still considered a full term baby.
When Does Labor Usually Start
Even though most babies are born during the 39th week, there is still a big range of what is considered normal.
Just because a typical pregnancy lasts 280 days doesn’t mean that your labor will start on day 280, or day 279 for that matter. No two women experience pregnancy the same way; likewise, no two women experience labor the same way. Even the same mama may experience big differences in how she recognizes the start of labor, what her signs of labor are, and then how long each of her own labors are.
Let’s take a look at what some mamas say about their own experiences:
- “My first was five days past my due date. My second was born on the due date that I calculated, but he was two days “late” by the doctor’s date. My third was born on her NFP due date.” — Jill
- “I went into labor two weeks early—at 38 weeks. With my second, I was two weeks—you guessed it—late.” — Maya
- “I went into labor with each of my three sons very late—42 weeks, 42 weeks, and 43 weeks.” — Patty
- “Spontaneous labor 36 weeks, and then 37 weeks for my second. No NICU needed.” — Rachel
How Late Can Babies Be Born?
Almost all babies are born within three (or even four) weeks of the due date, but most medical providers will not advise a pregnant mother to go past 42 weeks. Babies are very rarely born past 42 weeks, because labor is usually induced by 42 weeks if it doesn’t start spontaneously.
Going past 42 weeks is called “post term,” and studies show that inducing rather than going into “post term” reduces the risk of complications, including meconium aspiration, placental breakdown, c-section, and more.
When Should You Worry About Being Late?
For low-risk women there is evidence that with each day past the estimated due date, the risk of still birth begins to increase. The risk continues to increase slightly between 40 to 41 weeks and then becomes more exponential after 41-42 weeks gestation. Most providers from my experience recommend induction by 41 weeks for this reason. — certified nurse midwife Cynthia Mason
How far you can safely go past your due date depends on the following factors:
- A multiple pregnancy
- High blood pressure
- Autoimmune disorders, like Lupus
Bottom line: Although spontaneous labor is the goal, there is a time and place for encouraging labor to start.
Are First Babies Usually Late Or Early?
If you’re pregnant with your first, you might wonder when will my baby be born? Will my baby be late?
- Studies show that firstborn babies are up to 16 percent more likely to be born after their due dates.
- In contrast, second or third babies are only up to 10 percent more likely to be born after their due dates. (source)
But remember: Just because first babies have a higher chance of being born late doesn’t mean that all first babies will be late.
My Baby is Late, Now What?
It can be frustrating to see your due date come and go, but try not to stress! Try to savor this special time in your life.
“I recommend remaining active and living a typical day with a few added daytime naps. I usually also recommend that my patients go on dates with their partner and do lots of activities they enjoy. This may be the last time for a few months, or more, that the couple will have uninterrupted time.” — Cynthia Mason, CNM
That being said, it is very important to continue to follow up with your doctor or midwife. Your healthcare provider may want to monitor you closely to make sure baby is still thriving and has plenty of amniotic fluid.
If your provider suspects a reason to hurry Mother Nature along (such as your water breaking with no contractions in sight) , you may to start thinking about induction. Knowing your Bishop score can go a long way in helping you make informed decisions regarding induction options.
How About You?
When were your babies born? Late? Early? Right “on time?” Share your stories in the comments below!