Probability of delivery resulting from spontaneous labor after 35 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 9490 responses. 7210 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.

The statistics right now are as follows:

Data Table

The percentages are based on ALL births (including inductions)
DayWeekBirths Running TotalPercentRunning Total %
24535W,0D12120.1 % 0.1 %
24635W,1D15270.2 % 0.3 %
24735W,2D9360.1 % 0.4 %
24835W,3D21570.2 % 0.6 %
24935W,4D17740.2 % 0.8 %
25035W,5D18920.2 % 1 %
25135W,6D171090.2 % 1.1 %
25236W,0D281370.3 % 1.4 %
25336W,1D191560.2 % 1.6 %
25436W,2D331890.3 % 2 %
25536W,3D362250.4 % 2.4 %
25636W,4D302550.3 % 2.7 %
25736W,5D322870.3 % 3 %
25836W,6D333200.3 % 3.4 %
25937W,0D523720.5 % 3.9 %
26037W,1D514230.5 % 4.5 %
26137W,2D514740.5 % 5 %
26237W,3D725460.8 % 5.8 %
26337W,4D796250.8 % 6.6 %
26437W,5D666910.7 % 7.3 %
26537W,6D1067971.1 % 8.4 %
26638W,0D1099061.1 % 9.5 %
26738W,1D10010061.1 % 10.6 %
26838W,2D10511111.1 % 11.7 %
26938W,3D14512561.5 % 13.2 %
27038W,4D17314291.8 % 15.1 %
27138W,5D15415831.6 % 16.7 %
27238W,6D19817812.1 % 18.8 %
27339W,0D22820092.4 % 21.2 %
27439W,1D20222112.1 % 23.3 %
27539W,2D21924302.3 % 25.6 %
27639W,3D26426942.8 % 28.4 %
27739W,4D29829923.1 % 31.5 %
27839W,5D29632883.1 % 34.6 %
27939W,6D34636343.6 % 38.3 %
28040W,0D37640104 % 42.3 %
28140W,1D36143713.8 % 46.1 %
28240W,2D32046913.4 % 49.4 %
28340W,3D30549963.2 % 52.6 %
28440W,4D28452803 % 55.6 %
28540W,5D29655763.1 % 58.8 %
28640W,6D30358793.2 % 61.9 %
28741W,0D29361723.1 % 65 %
28841W,1D22063922.3 % 67.4 %
28941W,2D18465761.9 % 69.3 %
29041W,3D17967551.9 % 71.2 %
29141W,4D13268871.4 % 72.6 %
29241W,5D9869851 % 73.6 %
29341W,6D7470590.8 % 74.4 %
29442W,0D6171200.6 % 75 %
29542W,1D2371430.2 % 75.3 %
29642W,2D2471670.3 % 75.5 %
29742W,3D1371800.1 % 75.7 %
29842W,4D1171910.1 % 75.8 %
29942W,5D671970.1 % 75.8 %
30042W,6D472010 % 75.9 %
30143W,0D972100.1 % 76 %

Due Date Survey Data

Due date statistics: A study on the length of pregnancy
Probability of delivery resulting from spontaneous labor after 35 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

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Fast pregnancy calendar
Baby age calendar
EDD Icon Generator
Jo's Birth Story
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Recent Comments

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you are invited to join our pregnancy forum. We are dedicated to answering complicated questions as logically as we possibly can.

holiday shopping lists - kids/babies edition!

Wed Nov 25 11:20 AM by iamthegate in Pregnancy & Parenting

I know that for my niece, who has 3 pairs of grandparents and was the first grandkid of all of those, the parents put down a rule that every pair of grandparents could only gift one or two gifts, so she wouldn't get completely spoiled with gifts. The first year or two when they hadn't, stuff got a bit overboard (which was especially sad for my brother, who is just 4 years older than she is, and it's hard when someone else gets SO MUCH MORE gifts than he did).

I like buying books for kids. Even for very young ones, there are awesome books that can be read to them. Sadly, giving advice is hard, since most children's books I know are Dutch, and might not be translated.

Childbirth/infant cpr/baby care classes

Mon Nov 2 11:25 PM by antfancier in Pregnancy & Parenting

Thanks everyone! Lots for me to think about...

I have just started prenatal yoga and it seems that it will be pretty useful - although it's way more physical hard work than I expected (I'd better get used to it now, I guess).

Also, I hope I get an inflatable baby from whichever course I end up going with.

Postpartum girdle?

Fri Oct 23 2:47 PM by rowan in Pregnancy & Parenting

Interesting to hear everyone's stories about recovery. I still have issues with some of my ab muscles, I wonder if it would have helped.

OMG, twins! Advice & thoughts?

Mon Oct 19 5:27 AM by BabyTime in Pregnancy & Parenting

Hi :)

I have heard and I have noticed that in twins, one will be very active and one will be dull. Why it is happened with twins? Can anyone give justified answer to my question?

Red Raspberry Leaf capsules - ever helpful for labour or hokum?

Mon Sep 28 3:19 PM by artemiscuous in Pregnancy & Parenting

Oh, this is an interesting discussion and one that I'm finding interesting as I am in the early stages of my second pregnancy.

I really appreciate both perspectives represented here - of modern medicine and of herbalism - and I actually like a middle way of using both, insofar as they are meant to be used (I think both can be and often are misused and misunderstood). I think a well-studied use of herbal remedies can be very complimentary to good medical care. A friend of mine, who is a Western herbalist and clinical researcher, is very evidence-based and really changed my perspective on the place for herbs. It's easy for people to go overboard and claim too many benefits to herbal remedies, to push baseless hokum like homeopathy and chakra balancing, etc., and it's equally easy to denounce it all as unproven, because most clinical studies are not looking at herbs in a double-blind, well-constructed study, particularly in pregnancy, because of the risks if it is somehow dangerous (and many herbs can be, just because they can be quite potent, particularly in a tincture or other concentrated form).

medicated vs. unmedicated birth

Sun Nov 8 9:08 PM by ellarin in Pregnancy & Parenting

I used a midwife and had a home birth so as long as I was staying at home unmedicated was my only option. As I was home I was pretty much able to freely move around and labor however I felt comfortable. I also had access to a birthing pool which was a huge help for pain management and it also helped me to relax and kind of check out. My mantra was "I have to do this, so I will" I mean not exactly the most inspiring mantra out there but it worked for me. I just remember my husband and the midwives telling me repeatedly to breathe in through the nose, out through the mouth which is simple but it did help quite a bit.

I did have to lay on my back through a few of the early contractions for cervical checks and I found it VERY painful. If I had been at a hospital and needed to stay in bed on my back throughout the labor I think I probably would have found the idea of an epidural quite appealing. And ditto to what spacefem said regarding the after part... the most painful memory I have of my labor and delivery was the examination of my tearing after the birth. I think my natural endorphins where all tapped out by the time we got to that portion.

Letting kids use knives (and other dangerous implements)

Mon Nov 2 8:20 PM by lyra211 in Pregnancy & Parenting

When I was 7 we moved down the street from a 6-year-old boy whose dad owned a woodworking company. Little boy and I became pals, and his dad taught the two of us how to whittle not long after that -- as 6- and 7-year-olds messing with some pretty sharp Swiss Army-type knives, we retained all our digits and had a great time making whirligigs. His dad also taught us other basic woodworking, like hammering and whatnot, and other than a smashed finger or two we were none the worse for wear and I grew up pretty handy with some basic tools. No life-threatening injuries, and I can't even remember any slicing of fingers, although it seems as though there must have been some. I think kids are way more capable than we give them credit for, as long as they're properly instructed and supervised (obviously taking into account some judgment of the maturity level of the particular kid involved). It's hard to imagine a butter knife being a danger, and I can remember being pretty comfortable using my grandmother's steak knives to slice up a baked potato from an even younger age than the whittling.

Glucose Tolerance Test Problems

Tue Oct 20 3:26 AM by Bork in Pregnancy & Parenting

Definitely possible! I mean, the idea behind the tests is the same: measure an individual's reaction to a measured amount of glucose. The biology between GDM and T1DM are different, but at the end of the day I would think that the OGTT (glucose test) results would be similar enough. Although I guess there are so many more hormones in play with pregnancy that the results might end up being pretty different. I find it so disconcerting that doctors are like, "well, this test is somewhat unreliable but you should do xyz because FETUS" in cases like this.

We only tested our kids pre and post drink, since it was hard enough to get them to agree to two blood draws!

Altering my mind about pregnancy

Thu Oct 8 10:58 PM by lovernotafighter in Pregnancy & Parenting

Thank you everyone for invaluable opinions. I'm hoping I will not have to wait till my 40's, but I am 34 now, and the earliest I might have kids is probably 37. It will probably also take longer since I am in a same sex marraige, and ttc and all... Another consideration is that my wife is 13 years younger than I and she will be donating her young and healthy egg (hopefully) to me. So, my genetics will not be the only consideration. All factors I think about, and more... :) Thanks again everyone!

that time I got food poisoning when I was pregnant

Sat Sep 19 12:34 PM by spacefem in Pregnancy & Parenting

We have topics and questions all the time about what to eat when you're pregnant, so I wanted to share this charming story of an experience I had while pregnant with my second daughter.

I was only 10 or 11 weeks along and had been dealing with a "managable" level of morning sickness. This means that I could throw up at any time without warning, but in a cute pregnant way, not a dibilitating one. Most times, as long as there was food on my stomach I'd be okay, so I was careful to keep healthy snacks around - my favorite being cheetos, because you know, cheese is dairy right?

I was following all the good internet advice of not eating raw or uncooked foods, no deli meat, no salad bars, no soft cheeses, only low mercury fish, no food out of trunks of cars, etc.

We went to a wedding at a nice hotel. There was a buffet. I was one of the first people in line at the buffet because I had a two year old who looked like she might be hungry so I played that card, you know how it is. The food was delicious - salad with fresh lettuce, rice, beef strogonoff, mixed veggies. Everything that was supposed to be cold was cold and everything that was supposed to be hot was steaming hot.

Vent, advice: How to not be crazy at work...or in general

Wed Nov 4 3:23 PM by Maro in Pregnancy & Parenting

So, my pregnancy hormones are causing me major mood swings right now. I don't necessarily feel ashamed of it, but I'm frustrated enormously by it because I've got a ton of projects at work and a two-year-old to deal with, and I honestly do not have time to sit and cry for 30 minutes every few hours. I really hate being pregnant, for that and other reasons, but right now it's mostly that.

This morning I felt awesome and totally zen and amazing and only vaguely nauseated, and then a couple of things hit at work that I routinely eat for goddamn BREAKFAST and I'm a puddle of tears in my office. Luckily, I work from home so no one can see me, and all I can really do is push through it and keep getting stuff done. But it majorly sucked. Maybe there's no way around it...but if anyone has any ideas for coping with this stuff I'd be grateful. When you Google pregnancy hormones and mood swings the majority of advice is aimed at husbands "surviving" it, which immediately sends me into a rage spiral.

hospital vs homebirth

Sat Oct 24 8:02 PM by careme777 in Pregnancy & Parenting

The numbers don't lie. Home birth is several times riskier. For myself, being a risk averse type, I wouldn't choose it (even if I lived in a place where midwifery was licensed and part of the health care system.)

I'd be curious to know which numbers you're referring to. I chose to do a home birth (living in Canada, with government funded midwifery care) after a LOT of research (on an unrelated note, we ended up transferring to the hospital for a C-section during the pushing phase because baby wasn't turned correctly).

I read most of skepticalOB while trying to make my decision and did a basic (given my limited access to databases) lit review. My conclusion was that skepticalOB might have a point when discussing home birth in the US, because of the way midwifery care is stratified into certified nurse midwives and lay midwives. In mostly every other developed country with midwifery care, however, there is no conclusive evidence one way or the other that home birth is less safe than hospital birth for women with low risk pregnancies.


Mon Oct 19 1:05 PM by Sonic# in Pregnancy & Parenting

^ Should I stop doing one pro-health activity proven to stymie the spread of disease just because I have another one? It seems inaccurate to use cholera, a disease for which children in Western countries are not usually vaccinated for precisely the reasons you describe, to talk about all vaccinations. A better example is whooping cough, a highly contagious bacterial infection which doesn't need waterborne or foodborne vectors in order to travel and which vaccines prevent.

I don't think anyone here was saying vaccines are the only relevant factor. I heard Spacefem saying they're an important factor because even healthy living and good infrastructure won't prevent the spread of disease, and even good country living (not city living) is no panacea.

A bit aside from the topic, but I'm getting a flu vaccine this year because one of my colleagues cannot receive vaccinations due to a condition that suppresses her immune system. If I said, "Modern society is much cleaner nowadays and we eat a lot better, so I'm going to opt out of the vaccine and expect you to tough it out," I'd expect her to yell at me. Now, some of the hallmarks of that decision differ - I'm an adult who voluntarily takes the vaccine. The impact is similar - I reduce for the more vulnerable people around me (kids, elderly, anyone else with suppressed immune systems) the risks associated with infection.

Real stats for C-Sections?

Sun Oct 4 2:18 AM by Gnarlbanya in Pregnancy & Parenting

Thinking about this topic a little more, I think it's important that we remember that statistics just indicate trends and don't actually tell much of a story as far as individual circumstances go. By that I mean that while in some countries the c-section rate is statistically higher than in other places, it doesn't mean that an individual's decision to have a c-section in those countries is necessarily a flawed one. Nor does it mean that all doctors in those countries are scalpel-happy and just want to get babies out so they can take off to play golf or go for lunch, as I've seen it put on other pregnancy forums (not here).

If I do a brief statistical analysis of friends/acquaintances etc who have given birth in the last few years, the majority had vaginal births, everything from quick and uncomplicated to lengthy and forceps delivery. I can't think of any who had c-sections as a personal choice rather than for a medical reason. Those who had c-sections either had scheduled ones for good reason (obstruction due to fibroids, placenta previa, breech after unsuccessful ECV) or an emergency one for good reason (pre-eclampsia, fetal distress, placental abruption etc). Australia apparently has a c-section rate of 20-25% which this sample would accord with. But given the reasons for the c-sections, I do wonder when I read that the WHO recommends a c-section rate of 10-15%, who exactly should have been turned away from this limited sample?

Prenatal genetic testing

Thu Sep 17 9:08 AM by rowan in Pregnancy & Parenting

MOD HAT: I have moved the vaccination discussion to a new thread. Please discuss vaccines there.