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 6715 responses. 5040 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 75% 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,0D84841.3 % 1.3 %
26738W,1D811651.2 % 2.5 %
26838W,2D792441.2 % 3.6 %
26938W,3D1203641.8 % 5.4 %
27038W,4D1455092.2 % 7.6 %
27138W,5D1336422 % 9.6 %
27238W,6D1527942.3 % 11.8 %
27339W,0D1759692.6 % 14.4 %
27439W,1D16511342.5 % 16.9 %
27539W,2D16613002.5 % 19.4 %
27639W,3D22215223.3 % 22.7 %
27739W,4D22817503.4 % 26.1 %
27839W,5D24219923.6 % 29.7 %
27939W,6D27622684.1 % 33.8 %
28040W,0D29025584.3 % 38.1 %
28140W,1D28328414.2 % 42.3 %
28240W,2D25931003.9 % 46.2 %
28340W,3D24233423.6 % 49.8 %
28440W,4D22135633.3 % 53.1 %
28540W,5D23537983.5 % 56.6 %
28640W,6D22240203.3 % 59.9 %
28741W,0D23342533.5 % 63.3 %
28841W,1D16044132.4 % 65.7 %
28941W,2D13145442 % 67.7 %
29041W,3D13046741.9 % 69.6 %
29141W,4D10247761.5 % 71.1 %
29241W,5D8048561.2 % 72.3 %
29341W,6D6249180.9 % 73.2 %
29442W,0D4849660.7 % 74 %
29542W,1D2049860.3 % 74.3 %
29642W,2D2150070.3 % 74.6 %
29742W,3D1050170.1 % 74.7 %
29842W,4D950260.1 % 74.8 %
29942W,5D650320.1 % 74.9 %
30042W,6D150330 % 75 %
30143W,0D750400.1 % 75.1 %

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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My brief opinion on Ferguson and all that

Fri Nov 28 10:13 PM by monk in Random Weirdos

^That's where my dissconnect with the rioting comes in. I have this feeling (which may very well be wrong) that the people rioting in Ferguson are not at their limit but are taking advantage of a situation and I guess my beef is more with those that are looting than those that are just rioting.

favorite movie about anyone having a baby

Fri Nov 28 7:06 PM by tcook84 in Pregnancy & Parenting

My favorite movie is Knocked Up, it should definitely be on the list. Most of these movies I've never seen and some of them like Saved aren't solely focused on pregnancy. Out of the ones listed I would have to say "What to Expect when you're expecting".

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Fri Nov 28 6:52 AM by Meperidine in Random Weirdos

I got a comped ticket to the MoMA once when a friend worked there. I only had two hours to spend there, but easily could've spent 6. I don't think of museum-going as a particular interest of mine, but I was sucked into something new in every room. I haven't gone back, but I'd love to.

My parents dragged my sister and me to see "Carnation, Lily, Lily, Rose" and "Sunday in the Park" at the Chicago Art Institute when we were small. We didn't get there til near closing time, so we had to book it through the entire museum to get there for a few minutes' viewing, and we were tired and complained the whole time because we were children and jerks, but I admit I won't forget the paintings. Our parents cooed over the fact that the girls in "Carnation" could've been us, and the whole pointillism thing very much impressed me.


Thu Nov 27 8:11 AM by Mathmo in Random Weirdos

We've been decluttering / organising gradually for months now (and have got rid of lots of things! Lots have been recycled, or cleaned up and donated). I kind of like organising but only when there is enough space to actually put everything in. We've just moved house, so getting the volume of stuff to move down as low as possible for that was a big motivator. I read "The life-changing magic of tidying" by Marie Kondo a couple of months ago and rather liked it. She has a whole philosophy about tidying that I think makes a lot of sense (a practical approach which involves actually handling each item and seeing how you feel about it and saying goodbye gracefully to things).

I find it hardest to get rid of things I no longer want/need but that aren't in great condition - i.e. where I can see that there's still a lot of potential wear in them, but I don't think anyone would buy them from a charity shop. I really don't want to send things to landfill when they could still be used - but I can't keep all of them (current example: slightly stained but otherwise totally functional drawstring cotton laundry bag that I'm not super-fond of and don't need - bought in 2007 when I did need it for Uni ...).

forum suggestion box

Wed Nov 26 2:12 PM by spacefem in Random Weirdos


I fixed the chat pages, sorcery does have a web-based client that's working. next chat day is tuesday!

I forwarded the whole /chat to the wiki so we have one place to edit.

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Fri Nov 28 10:07 PM by monk in Pregnancy & Parenting

We have spent a lot of time babyproofing the dog, pestering it so it won't react negatively to ear and tail tugs.

Don't most dogs understand babies, like they do puppies? I know most of my friends with dogs haven't had a problem, you can even almost read the exasperation on the dog when the kid is screwing with it.

going public with the new pregnancy & parenting forum

Fri Nov 28 7:03 PM by rowan in Pregnancy & Parenting


Christmas gifts for small children

Fri Nov 28 4:18 AM by aka_laura in Pregnancy & Parenting

My baby needs diapers, since pooping is currently her favorite activity. An 18 month old in no way needs $2000 worth of gifts.

For older kiddos, I kind of like the "something you want, something you need, something to wear and something to read" thing. It's cheesy, but helps focus the holiday a bit.

I also like books, because I feel like someone really can't have too many books. They're easy to store, good for baby brains, and make good donation items if you do end up with a surplus.

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I almost never had to deal with this. I was living in a remote area and not interacting much with others. Also, the culture here doesn't seem conducive of interacting with people by touching them.

One of my spouse's young nieces touched my belly and I didn't know how to tell her not to do it. She was immediately corrected by her mother about not touching people without permission.

Then my parents arrived. I mostly just dealt with their touch, but probably not with much class.

Profile updates

Tue Nov 25 4:17 AM by cwbyrvr in Random Weirdos

My occupation used to be "college student/bum" which made it an interesting answer to what I wanted to be when I grew up for sure. Glad to see I wasn't the only one. I changed it, but I already forget what to... probably that I still don't know.

Hello friends!

Fri Nov 28 7:36 PM by rowan in Random Weirdos

Yay aka_laura's back!

And she's also my niece's mom!
waaaaaaait, what? O.o

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really you guys? I unfriend all the time!

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What's up?

Mon Nov 24 9:26 PM by DWH in Random Weirdos

Yooooooooooooooooo I keep forgetting to tell you I'm in LA until next Saturday and we should grab lunch if you're free!

Wait whaaaaaaaaaat, okay, I'm leaving town tomorrow for Thanksgiving but I'm going to move this discussion to Facebook.

And MFS, of course you should be scared. BAHAHAHAHA