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The Odds of Baby Arriving on Their Due Date?

Without a doubt, you’ve heard lots of conflicting information on what a due date actually is.

Most believe the due date is a deadline. If Baby doesn’t arrive on that date, she’s late. If Baby comes before then, she’s automatically “premature.”

Some have theorized that due dates are an invention of modern medicine, and have become an excuse for doctors to perform c-sections. While that’s not what we believe, we do know that due dates are often inaccurate.

Baby should not be expected to arrive on an exact day (unless you’ve scheduled a c-section).

In fact, Baby should not be rushed at all unless there’s a medical reason to do so. According to the March of Dimes, a non-profit that “works to end premature birth, birth defects and infant mortality:”

“Labor should be induced only for medical reasons to protect the health of you and your baby. If your pregnancy is healthy, it’s best to let labor begin on its own without inducing labor.” // MarchofDimes.org

Due Date Statistics

Let’s take a look at the statistics taken from a casual, online survey with 11,704 participants. You can also take the

Due Date Statistics

Let’s take a look at the statistics taken from a casual, online survey with 11,704 participants. You can also take the

Note: The survey results were not verified. They rely on the honesty and accuracy of online participants. You can also take the  survey here at SpaceFem.com.

  1. What is the probability of spontaneous labor after 35 weeks?

Out of 11,1114 women, 8,464 went into labor spontaneously. This equals 76% of the total participants.

  1. What is the probability of giving birth within X days of your due date?

Do babies come on their due dates? Not really, but they usually come sometime around it. Only 4.3% of babies arrived on their due date. Comparatively, 61.6% of non-induced babies arrive within one week of their due date.

  1. What is the average length of pregnancy in weeks?

  • 31.8% of babies were born at 40 weeks
  • 25.7%  were born at 39 weeks
  • 16.1% of babies were born at 41 weeks
  • 13.5% were born at 38 weeks
  • 6.4% were born at 37 weeks
  • 2.8% were born at 36 weeks
  • 2.1 % were born at 42 weeks
  • 1.5% were born at 35 weeks
  • 0.1% were born at 43 weeks.
  1. What is the average length of pregnancy for subsequent births?

If your first baby comes early, will your second baby be early, too? If your second baby arrives late, does that mean your third will come late as well? According to the survey, on average, subsequent babies arrive 0.18 days later than the previous baby.

  • The average baby #2 came 0.44 days later than baby #1, based on 900 mothers.
  • The average baby #3 came 0.73 days earlier than baby #2, based on 187 mothers.
  • The average baby #3 came 0.58 days earlier than baby #1, based on 184 mothers.
  • The average baby #4 came 0.92 days earlier than baby #3, based on 50 mothers.
  • The average baby #4 came 0.19 days earlier than baby #2, based on 47 mothers.
  • The average baby #4 came 0.38 days earlier than baby #1, based on 48 mothers.
  1. What is the length of pregnancy for first-time moms compared to second- and third-time moms?

On average, a first-time mom has her baby at 39 weeks 5 days. This is the equivalent of 54.8% of first-time moms giving birth on or before their due date compared to 56.7% of second-time moms, and 59.5% of third-time mothers.

  1. Is there a connection between length of pregnancy and the type of delivery?

  • 9% of the 8,670 women who went into labor spontaneously underwent a c-section.
  • 19% of 2,343 women who were induced underwent a c-section.

Is there a correlation between induction and increased incidence of cesarean? You decide.

  1. What is the relationship between the length of pregnancy and birth weight?

Are “late” babies huge? On average, “late” babies are generally bigger than “early” ones but not by much. The difference between a baby born at 39 weeks and one born at 41 weeks is about 300 grams.

  1. What is the probability of induction after the due date?

Most doctors will induce a mom rather than let her get past her due date. According to the March of Dimes, however:

“If your health care provider talks to you about inducing labor, ask if you can wait until at least 39 weeks to be induced. This gives your baby’s lungs and brain the time they need to fully grow and develop before he’s born.” // MarchofDimes.org

  1. Is there a correlation between the age of the mother and the probability of spontaneous labor?

It has been theorized that the age of the mother has something to do with when labor sets in. Is it possible that the average due date would change depending on ethnicity, age or even country of origin? According to the survey, about the same number of women give birth on day 279 as 287.

  1. Are more babies born on a full moon?

There is no correlation between the phase of the moon and when babies are born.

  1. What is the most common day of the week for babies to be born?

According to the survey, the most common day for babies to be born is Thursday while the least common is Saturday.

  • Sunday 10.6% spontaneous deliveries and 1.6% induced births.
  • Monday 11% spontaneous deliveries and 3.2% induced births.
  • Tuesday 10.7% spontaneous deliveries 4.1% induced births.
  • Wednesday 10.9% spontaneous deliveries 3.9% induced births.
  • Thursday 13.1% spontaneous deliveries 4.5% induced births.
  • Friday 10.6% spontaneous deliveries 3.9% induced births.
  • Saturday 10% spontaneous deliveries 2.3 % induced births.
  1. What does it mean if I’m 40 weeks pregnant?

Congratulations! You’ve hit your due date and Baby is fully developed! Instead of stressing out that Baby’s not here yet, relax and enjoy the anticipation. 52% of the women surveyed were still pregnant at 40 weeks. 28.79% of babies were born spontaneously within the next 3 days (on or before 40W,3D).

It’s normal to still be pregnant at this point. If your doctor or midwife is supportive of natural induction, consider these natural induction methods.

  • 34.49% of babies were born spontaneously within the next 4 days (on or before 40W, 4D)
  • 46.57% of babies were born spontaneously within the next 6 days (on or before 40W, 6D)
  • 57.07% of babies were born spontaneously within the next 8 days (on or before 41W, 1D)
  • 68.61% of babies were born spontaneously within the next 12 days (on or before 41W, 5D)
  • 73.44% of babies were born spontaneously within the next 21 days (on or before 43W, 0D)
  • 26.56% of babies were induced.
  1. I know the exact date I conceived. Can I calculate my exact due date?

Typically, due dates have an 8- to 10-day variation as they are calculated from the last menstrual period, not date of conception. The question then arises, is it possible to calculate an exact due date based on conception date?

According to the survey, the standard deviation does not improve even if you know the exact second your baby was conceived.

Babies are individuals, just like adults. Some need more time in the womb than others.

  1. Which babies are born earlier, boys or girls?

The average arrival time for babies of both sexes  is 39 weeks and 5 days.

  1. Do inductions bias due date  statistics?

What if all the women who were induced were meant to give birth late? Doesn’t this change the average amount of time a pregnancy should last? Not really, according to the survey. If we assume each induction was actually a late birth, the average median would shift by 2 days.

 

First Published at www.spacefem.com.

Featured image source: www.sheknows.com

Leah

Owner, Founder at Karangis Collections
Leah was born and raised in Kenya. She has a degree in psychology and divides her time between article writing, blogging and creating original African pieces.

She provides her writing services independently and can be found odesk. When she isn’t hunched over a computer, she’s out being inspired by nature.


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