Probability of delivery within x days of a given date

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This graph shows only babies born as a result of spontaneous (non-induced) labor (76% of all participants).

Do babies come on their due dates? Not really. But they seem to come around their due dates. In the survey, only 477 out of 10990 (4.3%) spontaneously arrived on the exact day. But if you look around that date, the numbers get bigger fast... 2722 babies (24.8%) arrived spontaneously between 39 weeks 4 days and 40 weeks 3 days. 5146 (46.8%) arrived spontaneously within a week of their due date. Throwing out inductions makes those percentages even higher: 61.5% of all non-induced babies arrived within a week of their due date.

I also think this graph is important because it shows how meaningless it is to move a due date one or two days. For example I have a chart comparing first time moms to mothers who've had previous births, and it shows about a 1-2 day difference. But based on this graph, who cares about a day?

What I mean is this: a woman who's not induced has a 61.5% chance of giving birth within a week of her due date. Let's say we lie to her and tell her a date that's three days early. Now she has a 60.4% chance of delivering within a week of that "wrong" date. It's not really a huge difference.

Data Table

DayIn weeksBabies Spontaneously Born
24535W,0D14
24635W,1D17
24735W,2D12
24835W,3D22
24935W,4D19
25035W,5D21
25135W,6D18
25236W,0D32
25336W,1D25
25436W,2D35
25536W,3D37
25636W,4D32
25736W,5D35
25836W,6D40
25937W,0D62
26037W,1D59
26137W,2D62
26237W,3D76
26337W,4D87
26437W,5D79
26537W,6D118
26638W,0D132
26738W,1D117
26838W,2D121
26938W,3D162
27038W,4D199
27138W,5D174
27238W,6D226
27339W,0D262
27439W,1D230
27539W,2D260
27639W,3D315
27739W,4D342
27839W,5D338
27939W,6D399
28040W,0D477
28140W,1D438
28240W,2D373
28340W,3D355
28440W,4D324
28540W,5D340
28640W,6D347
28741W,0D346
28841W,1D251
28941W,2D204
29041W,3D203
29141W,4D143
29241W,5D112
29341W,6D90
29442W,0D70
29542W,1D26
29642W,2D26
29742W,3D22
29842W,4D12
29942W,5D10
30042W,6D8
30143W,0D11

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

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
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Recent Comments

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Carriers vs Ring Sling

Mon Aug 29 4:18 AM by antfancier in Pregnancy & Parenting

If you are is the USA, then Babywearing International (http://babywearinginternational.org/about-bwi/chapters/) may have a group near you. You could also try going to a baby & kids store which has carriers you can try on there before you buy. I definitely recommend trying on first - baby carriers are expensive and you want to make sure you have a good fit. As Rowan said, it's a very personal preference that depends on your baby's size and your own body type, as well as your lifestyle and the climate where you live.

If you do decide to go for one of the more expensive ones, you can get some good deals on used carriers that are still in great condition. I have seen a lot of Ergo carriers for sale on Craigslist and if you use Facebook there are some sales groups too - search for Babywearing On a Budget, which serves North America.


How to Announce Baby #4?

Mon Aug 1 10:44 PM by rowan in Pregnancy & Parenting

eh go ahead and eat them. I recommend ketchup, though. Or hot sauce.

Oh and congratulations and all that, it'll be fine. :) People do get weird but here are some random responses:
"well, I guess we were wrong!" cheerfully
"Shit, we we were wrong. OH well.
"IDK do you think we should get rid of one of the others?"
"You want one?"
"Well we weren't sure the first three would be enough sustenance when the apocalypse comes"
"We have W girls and Z boys, we're hoping for something in between"
"Actually we're hoping it's a cat"
"Did you realize that we just sent a new spacecraft to Jupiter? Isn't that exciting!"


Denial Trends?

Thu Jul 21 7:24 PM by SameMom in Pregnancy & Parenting

Sorry, if I was not able to mention other details. Actually, I have a (US) medicare insurance. And I am particularly referring to this denial management software which help clients with their claims. Thanks for your reply. :)


minimalist kids birthday parties

Sun May 15 9:19 PM by melsbells in Pregnancy & Parenting

For the first two birthdays, we tried to make some special food and splurge on interesting fruit. If I lived closer to friends, I would want to throw a get-together as an excuse to see my friends, celebrate our survival of another year. I don't think my kid would actually be into that though. They are turning out to be quite introverted and shy.


7th Birthday - Theme Suggestion

Mon May 2 8:18 PM by melsbells in Pregnancy & Parenting

I met a kid about that age who had a geo-caching birthday party and another one who had a roller-skating party. Both sounded awesome. The first one sounded like a whole lot of work to put together.


Cry it out vs. Attachment

Mon Aug 29 3:56 AM by Taurwen in Pregnancy & Parenting

I wonder what other primates do and if it varies much from family to family or within family.

Do other primates have screaming babies?

I took a few physical anthropology courses in school (Mostly classes on primates) and I now have an infant. It's amazing how often I think "Oh man, that's exactly how a baby capuchin monkey would act!" when he freaks out. Mostly baby primates just freak out when separated from their mother, their mothers deal with this by letting their young be attached to them pretty much 24/7


it gets better thread for parents

Fri Jul 29 1:26 AM by curlybae in Pregnancy & Parenting

It's true though. You don't get a good night's sleep until they're an adult. Looking back, I don't think my mom slept a wink my baby brother was born lol


Public Service Announcement: Furniture Anchors!

Fri Jul 1 5:17 AM by cwbyrvr in Pregnancy & Parenting

I do find it very interesting to find that IKEA is recalling furniture because people don't secure it to walls... I was given anchors with all of the stuff I've bought from there. Though maybe that's only a somewhat recent thing? It was over a half a year ago that I bought stuff from there, though.

And I didn't use the anchors... I guess I am about to be an aunt and it might be a good idea to get that stuff secured in case I ever end up watching my niece here. Hadn't really worried about it prior because there was literally never going to be a time I'd have kids running around this place. The likelihood of my niece ever being here is pretty damn low too, but I wouldn't say 0%.


Pregnancy Guidebooks for Cool Moms (humor)

Wed May 11 3:39 PM by rowan in Pregnancy & Parenting

One of my friends is part of this magazine. She didn't write this one but it's pretty hilarious.

http://theoffingmag.com/wits-end/pregna ... cool-moms/

Anyone want to come up with our own "Guidebook" titles?

spoiler:
the one about inducing labor by setting your hair on fire is my favorite


stuttering at the end of words

Thu Apr 28 9:21 PM by Sonic# in Pregnancy & Parenting

I don't think it's a cause for immediate concern, but my experience would lead me to talk to a doctor about it. I didn't have a stutter when I was 2. I had language delay. I didn't learn language when kids typically do. Needless to say, I was a very frustrated little kid. When my parents and my pediatrician caught on to it, I had to spend a few years seeing a speech pathologist.

I've read that stuttering is at least partly psychological, but I really can't say more than that. If nothing else, I'd just want to know that his frustration is a necessary part of development like teething and not something that can be avoided.


Do you use boil bags?

Mon Aug 8 3:20 PM by Sonic# in Pregnancy & Parenting

All I can think of is the Arrested Development episode where George Bluth Sr. has a hot tub installed in his attic hiding place so that he can boil food in the bag.

I've not boiledfood in a bag, but not due to any aversion.


How NOT to help parents with a newborn

Fri Jul 22 6:11 PM by missmay in Pregnancy & Parenting

oh, lord, i am so tired of people telling me to "enjoy it!" regarding my newborn. and asking me if she is a "good baby." how could a baby be bad? and how does it make me enjoy her more to be reminded to do so? i imagine that if i was depressed and had a colicky baby these questions would be even more obnoxious.


Kids are full of LIES

Sun May 22 2:29 PM by rowan in Pregnancy & Parenting

Don't be silly monk, everyone knows a good conglomerate goes better with milk


young kids, consent and bodily autonomy

Mon May 2 8:46 PM by monk in Pregnancy & Parenting

I think it depends on the child. Do you ask a newborn if it needs it's diaper changed? Obviously no. Do you help a 13 year old get dressed? Obviously no. Somewhere in there the child matures to the point where they should learn that they own their bodies even if they don't have all the privileges an adult does. This age is going to vary wildly between different children (by widly, I would say 3 year range). I would guess that some kids might be ready for this lesson as early as 3 while others not until they're about to go school. Actually that's a pretty good benchmark, because if you're going to put them in a group with other kids they don't know they should know the rules about touching or being touched.

As far as kissing Grandma, maybe they shouldn't have to do it, but making them do this social communcation helps get them ready for all the other social communication that will be forced on them later. Plus, grandma needs that love to help HER be healthy.


test out my new name picker

Fri Apr 15 11:41 PM by rowan in Pregnancy & Parenting

my neighbor's dog is named Gunner? Makes more sense for a bird dog....