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 10357 responses. 7873 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,0D13130.1 % 0.1 %
24635W,1D16290.2 % 0.3 %
24735W,2D11400.1 % 0.4 %
24835W,3D22620.2 % 0.6 %
24935W,4D18800.2 % 0.8 %
25035W,5D201000.2 % 1 %
25135W,6D181180.2 % 1.1 %
25236W,0D281460.3 % 1.4 %
25336W,1D231690.2 % 1.6 %
25436W,2D332020.3 % 2 %
25536W,3D362380.3 % 2.3 %
25636W,4D302680.3 % 2.6 %
25736W,5D333010.3 % 2.9 %
25836W,6D353360.3 % 3.2 %
25937W,0D563920.5 % 3.8 %
26037W,1D564480.5 % 4.3 %
26137W,2D555030.5 % 4.9 %
26237W,3D735760.7 % 5.6 %
26337W,4D846600.8 % 6.4 %
26437W,5D767360.7 % 7.1 %
26537W,6D1148501.1 % 8.2 %
26638W,0D1229721.2 % 9.4 %
26738W,1D11210841.1 % 10.5 %
26838W,2D11612001.1 % 11.6 %
26938W,3D15313531.5 % 13.1 %
27038W,4D18315361.8 % 14.8 %
27138W,5D16216981.6 % 16.4 %
27238W,6D21319112.1 % 18.5 %
27339W,0D24621572.4 % 20.8 %
27439W,1D21823752.1 % 22.9 %
27539W,2D24526202.4 % 25.3 %
27639W,3D29829182.9 % 28.2 %
27739W,4D32532433.1 % 31.3 %
27839W,5D31935623.1 % 34.4 %
27939W,6D37639383.6 % 38 %
28040W,0D42543634.1 % 42.1 %
28140W,1D40047633.9 % 46 %
28240W,2D34451073.3 % 49.3 %
28340W,3D34154483.3 % 52.6 %
28440W,4D31257603 % 55.6 %
28540W,5D32560853.1 % 58.8 %
28640W,6D32964143.2 % 61.9 %
28741W,0D32267363.1 % 65 %
28841W,1D23869742.3 % 67.3 %
28941W,2D19671701.9 % 69.2 %
29041W,3D19873681.9 % 71.1 %
29141W,4D13875061.3 % 72.5 %
29241W,5D11076161.1 % 73.5 %
29341W,6D8477000.8 % 74.3 %
29442W,0D6877680.7 % 75 %
29542W,1D2477920.2 % 75.2 %
29642W,2D2578170.2 % 75.5 %
29742W,3D1978360.2 % 75.7 %
29842W,4D1178470.1 % 75.8 %
29942W,5D978560.1 % 75.9 %
30042W,6D678620.1 % 75.9 %
30143W,0D1178730.1 % 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
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EDD Icon Generator
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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.

Criminalization of drug use during pregnancy to end in Tennessee

Mon May 2 11:14 AM by Lia913 in Pregnancy & Parenting

That's good news! I believe a woman should stop taking drugs or drinking alcohol (or smoking) immediately after she had unprotected sex in case she's pregnant. And a woman can be pregnant even if she had sex during period. So, the actions of the authorities seem a necessary measure.


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.


Pets and newborns

Tue Mar 22 2:34 AM by codingchemist in Pregnancy & Parenting

It's really obvious that the dog is stressed out by the toddler and I'm worried about the times when the kid is showing too much interest in the dog and we're not paying enough attention.

Yeah-stressed out dogs can make for stressful times with toddlers. Toddlers just want to pet and hug, and don't want to listen to pleas to leave the dog alone. We wound up getting an automatic treat dispenser and giving the dog relaxation exercises behind a barrier. So now when the toddler is running the length of the house screaming, the dog can be behind the barrier staring lovingly at her treat dispenser, instead of trying to herd the kid. Of course, it isn't really feasible to keep the dog behind the barriers at all times, but at least it gives us some breaks.

Our behavioralist also recommended Prozac, which took a long time to get the dose right, but has helped the dog be less reactionary and neurotic.


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Thu Mar 3 10:36 PM by curlybae in Pregnancy & Parenting

Hi! It's a great idea to throw a party for your Mom. So yeah, invite her good friends and those who she hasn't seen for quite some time already. Prepare some healthy food or you can get a caterer for this tell them to prepare your mom's favorite dishes. Set up a good sound system where they can opt to dance or sing their old fav songs. Request her friends to prepare a great birthday greetings and i'm sure she won't forget this event.


Flying while pregnant, Split from Cartoons for Little Girls in Feminism

Thu Feb 18 1:01 AM by trillianastra in Pregnancy & Parenting

Sassquatch, that's what I was wondering too! A friend who has three kids gave me some great advice about being pregnant. She said, "You're going to get advice from everyone. Feel free to ignore it unless it comes from your doctor!" (And she's a nurse, so for her to even exclude herself from the "advice-giving" permission list was crazy, IMO!)


Advice for surviving the last days of pregnancy?

Mon May 2 11:13 AM by Lia913 in Pregnancy & Parenting

Think about everything you would like to do with your child after birth. How you'll take care of the baby? Who will your baby look like? Think about breastfeeding, maybe (sorry that I suggested this topic if you're not going to BF): it has it's advantages, but it's still not for everyone. Or you can just read a good book! :)


Umbilical cord

Wed Apr 27 1:26 AM by antfancier in Pregnancy & Parenting

There's a Bulgarian tradition about the umbilical cord my friend told me about. When the dried little stump falls off your baby, you're supposed to throw it in a place that reflects your child's future, or at least the future you want for them. My friend threw his first son's on to the pitch at a Yankees' game and for his second son he threw it at the stage during a concert!

When my son's cord fell off a few weeks ago, I put it on the counter next to his changing pad then promptly forgot about it. I've no idea where it is now.


Sperm Can be Cultivated from Skin Cells

Thu Mar 10 6:56 PM by rowan in Pregnancy & Parenting

Pretty sure this was a spam post but the post itself is kind of interesting. Maybe it could go to Sci & Tech, though it has relevance here as well. I added a link to the Science article, in case anyone wants to read it.


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Mon Feb 22 5:28 PM by rowan in Pregnancy & Parenting

oh re: diaper rash, we found our kiddo was super sensitive and when things go really bad we got something prescribed from the doc that worked *wonders*. IDEK why that stuff isn't marketed, the pharmacist mixed it all up. The doc called it "poop goop" but I dunno what was in it.


spacefem's guide to baby-led weaning

Tue Feb 16 9:21 AM by Gnarlbanya in Pregnancy & Parenting

Thanks for the advice everyone. We had a bit more success after a second go, I did some steamed carrot sticks as well, and I think she liked the variety in shapes and colour. I think I did originally cut the apple too small as she had an easier time with the carrot. Some even made it into her mouth! Mostly, though, she wanted to gnaw on the bowl or the high chair tray.

I did a baby first aid course recently, so I just need to remind myself that I know what to do if anything does go wrong. I have developed a definite fear of grapes over this weaning business, though!

Metcodon, she's five days younger. Good to know that some babies prefer the mashed stuff. I might broaden out to a few other fruits, perhaps even some stuff that is soft enough to not bother steaming, and if she doesn't like it in stick/chunk form I can just mash it up for her anyway.


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Sun May 1 11:04 PM by curlybae in Pregnancy & Parenting

Hi! My niece is turning 7 yo this June and I was requested by my brother to help them come up with a good theme. She loves Frozen and Little Pony but these 2 are quite common already. I want to suggest something that is not related to any cartoon character...what about a Hawaiian party since it's summer? Can you suggest any other interesting themes, please? TIA.


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....


Why have children if you want to work (aka it's 1950!)

Tue Mar 8 9:16 PM by antfancier in Pregnancy & Parenting

I just had a look at your article. :thumbup:
As you say, many comments have been deleted, but that's probably for the best otherwise I'd get mad.

I'm about to have my first child and have had some similarly surprising responses from people when I explain I'm going to be a SAHM; everything from admiration to unsolicited suggestions that a nanny is better than daycare. When I explain that the reason is that I acut ally want to work but my earnings from my two part time jobs would barely cover childcare, it always gets awkward. And then they suggest the whole home daycare/nanny thing again. Even if I could afford it, I'd rather choose the daycare because they have facilities and resources that I don't (I live in a basement apartment, with pretty minimalist furnishings).

I get it. People have strong beliefs about what is 'best', but it's not a one-size-fits-all scenario. And holy crap! If a woman wants and is able to work after having kids, why on earth shouldn't she?


warning: when your baby sleeps through the night...

Fri Feb 19 3:18 AM by rowan in Pregnancy & Parenting

We didn't get the sleepwalking (thankfully) but demonic possession seems about right. It presented a lot like a horrible nightmare with very loud screaming/crying, but we couldn't wake her up from it. She wouldn't remember it at all in the morning, at least. We did find that sometimes we could 'interrupt' it by either singing or telling her stories about something completely random, but what was effective one night often was not effective the next so it was constantly trying something new. Over time the singing seemed to work better and better until they (mostly) went away, but it took a very long time.

I think the hardest was the feeling of complete helplessness to stop it. :( But like I said she never remembered any of it.


The pregnant woman's business trip from hell (or at least heck)

Sat Feb 6 5:09 PM by lyra211 in Pregnancy & Parenting

Yeah, I went back and checked some sources -- here's the table that I sort of remembered from when I was going through the ectopic scare:
http://www.advancedfertility.com/ectopic.htm
So, half of ectopic pregnancies never get above an hCG level of 1,000, and only 9% ever make it above 10,000. Needless to say, the ones that do keep rising to those very high levels tend to be the scary ones, since those are the ones that keep growing and can cause things like tubal ruptures.

I can't link to it because it's subscriber only, but Up To Date (which has reviews of the most recent medical studies) has the following to say about the hCG threshold of 2,000 (some practices use 1,500 instead) and diagnosis of ectopic pregnancy:

The diagnostic criteria depend upon the relationship to the hCG discriminatory zone (serum hCG level above which a gestational sac should be visualized by TVUS if an IUP is present). The hCG level of the discriminatory zone varies, but in most institutions it is 1500 to 2000 IU/L (see 'Discriminatory zone' above and 'Clinical protocol' above):