Probability of delivery resulting from spontaneous labor after 38 weeks

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The most important question I was trying to answer with the survey was this: "When is a baby most likely to spontaneously show up?" The graph above shows the percentages, based on 7865 responses. 5949 of the deliveries were as a result of labor occuring spontaneously. The chart only shows these deliveries, which is why the percentages do not add up to 100%, because only 76% of participants had spontaneous (non-induced) labor.

This page shows what day you'll likely give birth, if you're still pregnant at 38 weeks. To find out how week 38 compares to the other weeks overall or to find out the probability of delivery at 38 weeks, refer to the Length of pregnancy by week chart.

The statistics right now are as follows:

Data Table

The percentages are based on ALL births (including inductions)
DayWeekBirths Running TotalPercentRunning Total %
26638W,0D1021021.3 % 1.3 %
26738W,1D992011.3 % 2.6 %
26838W,2D932941.2 % 3.7 %
26938W,3D1344281.7 % 5.4 %
27038W,4D1665942.1 % 7.6 %
27138W,5D1487421.9 % 9.4 %
27238W,6D1889302.4 % 11.8 %
27339W,0D20711372.6 % 14.5 %
27439W,1D18713242.4 % 16.8 %
27539W,2D20415282.6 % 19.4 %
27639W,3D24817763.2 % 22.6 %
27739W,4D27720533.5 % 26.1 %
27839W,5D27223253.5 % 29.6 %
27939W,6D31926444.1 % 33.6 %
28040W,0D34729914.4 % 38 %
28140W,1D33333244.2 % 42.3 %
28240W,2D29636203.8 % 46 %
28340W,3D28639063.6 % 49.7 %
28440W,4D26541713.4 % 53 %
28540W,5D27544463.5 % 56.5 %
28640W,6D27347193.5 % 60 %
28741W,0D27949983.5 % 63.5 %
28841W,1D19551932.5 % 66 %
28941W,2D16053532 % 68.1 %
29041W,3D16655192.1 % 70.2 %
29141W,4D12556441.6 % 71.8 %
29241W,5D8957331.1 % 72.9 %
29341W,6D7058030.9 % 73.8 %
29442W,0D5958620.8 % 74.5 %
29542W,1D2358850.3 % 74.8 %
29642W,2D2259070.3 % 75.1 %
29742W,3D1359200.2 % 75.3 %
29842W,4D1159310.1 % 75.4 %
29942W,5D659370.1 % 75.5 %
30042W,6D359400 % 75.5 %
30143W,0D959490.1 % 75.6 %

Due Date Survey Data

Due date statistics: A study on the length of pregnancy
Probability of delivery resulting from spontaneous labor after 38 weeks
Probability of delivery within x days of a given date
Length of pregnancy by week
Spontaneous labor and due date determination
Length of pregnancy, comparing subsequent births for individual moms
Length of pregnancy for first time vs. second & third time moms
Length of pregnancy, type of delivery
Gestation vs. Birthweight
Probablity of Induction after a given day
Average day of spontaneous labor vs. age of mother at time of birth
Are more babies born during a full moon?
What's the most common day of the week for babies to be born?
I'm still pregnant at 40W. What's it mean?
Do winter babies arrive later?
What if I know my conception date?
Are boys or girls born later?
Subsequent pregnancy date search
How do inductions bias the due date statistics?
Birth Stories
Survey input dates

More Resources

Pregnancy Day-by-Day
Fast pregnancy calendar
Baby age calendar
EDD Icon Generator
Jo's Birth Story
Weeks vs. Months Explained
Charts generated by flot

Recent Comments

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Thu Jul 30 11:41 AM by DarkOne in Pregnancy & Parenting

A few of the more enterprising/crafty moms in my old parent group got together with a group of friends and bought beads in bulk from alibaba or some other site like that. Some sold the necklaces locally, some made really affordable gifts for friends; I almost jumped in, because a couple of years ago these were still hovering at the $30 mark, but at ~$15, they're much more affordable now, methinks.

They babies I witnessed munching on these were really going to town on them, too.

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Tue Jul 28 7:24 PM by ladyhawk in Pregnancy & Parenting

Mine started walking. :( SO not ready for two kids running around getting into things.

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Tue Jul 21 2:28 AM by DarkOne in Pregnancy & Parenting

Eek and here I was about to say this felt like a tame version of Mother Lover.

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Sorry to CPR a dying thread, but I came across this, and thought I'd share.


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Thu Jun 25 1:03 AM by Aum in Pregnancy & Parenting ... ssion.html

Pre and post-partum depression have similar reasons, physically speaking. Check nutrition first.

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Thu Jul 30 8:38 AM by melsbells in Pregnancy & Parenting

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A parent in my Kindergarten class would bring us homemade purple play dough that smelled like grape!


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Thanks! I was going to put my labor story in Random but never got around to it. I can try to do it soon - it's written out already so just a matter of editing.

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