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 425 out of 10354 (4.1%) spontaneously arrived on the exact day. But if you look around that date, the numbers get bigger fast... 2530 babies (24.4%) arrived spontaneously between 39 weeks 4 days and 40 weeks 3 days. 4822 (46.6%) arrived spontaneously within a week of their due date. Throwing out inductions makes those percentages even higher: 61.3% 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 61.3% 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 60.3% chance of delivering within a week of that "wrong" date. It's not really a huge difference.

Data Table

DayIn weeksBabies Spontaneously Born
24535W,0D13
24635W,1D16
24735W,2D11
24835W,3D22
24935W,4D18
25035W,5D20
25135W,6D18
25236W,0D28
25336W,1D23
25436W,2D33
25536W,3D36
25636W,4D30
25736W,5D33
25836W,6D35
25937W,0D56
26037W,1D56
26137W,2D55
26237W,3D73
26337W,4D84
26437W,5D76
26537W,6D114
26638W,0D122
26738W,1D112
26838W,2D116
26938W,3D153
27038W,4D183
27138W,5D162
27238W,6D213
27339W,0D246
27439W,1D218
27539W,2D245
27639W,3D298
27739W,4D325
27839W,5D319
27939W,6D376
28040W,0D425
28140W,1D400
28240W,2D344
28340W,3D341
28440W,4D311
28540W,5D325
28640W,6D327
28741W,0D322
28841W,1D238
28941W,2D196
29041W,3D198
29141W,4D138
29241W,5D110
29341W,6D84
29442W,0D68
29542W,1D24
29642W,2D25
29742W,3D19
29842W,4D11
29942W,5D9
30042W,6D6
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

For more support, encouragement, Q&A,
you are invited to join our pregnancy forum. We are dedicated to answering complicated questions as logically as we possibly can.

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.


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....


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.


Advice on dealing with a sick baby

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.


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.


Criminalization of drug use during pregnancy to end in Tennessee

Tue Mar 29 2:48 AM by Amuro in Pregnancy & Parenting

Actually I think it would be better if the penalty was rehab and being sent to a therapist. It's pretty dumb to criminalize it especially because there is an almost certainty custody will be taken away. Why not try and fix the problem with addiction so there is less of a strain on social services. There should be increased awareness but what idiot doesn't know drugs are bad for you and worse if your pregnant. If you are addicted to drugs you obviously are thinking about getting high and that's about it.


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):


Advice for surviving the last days of pregnancy?

Tue Apr 26 10:47 AM by AmanadaMiller in Pregnancy & Parenting

Hi, Lyra211,

I hope you are doing good. First of all congrats for your pregnancy. Iím writing this while 38 weeks pregnantĖnot dilated, not effaced, no contractions, nothing. This is my third baby. The first two had to be evicted or they might have stayed in there forever (at least thatís how it felt at the time). I know not all women go all the way to the due date or beyond, but for those who do, we share this in common: the last month is tough!
You feel huge, uncomfortable, and probably a little (or a lot) impatient. Time seems to move in slow motion. The aches increase by the day. Itís impossible to make plans. Youíre more than eager to meet your little kicker on the outside.

Iím experiencing this ďwaiting gameĒ for the third time right now. I canít wait to meet my little girl! But after doing this a couple times, I have to say that itís a little easier this time around. Here are some tips that can hopefully help you make the most of the last month.


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.


Party For My Mom

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!)


the unplanned homebirth

Tue Feb 2 11:37 AM by Aum in Pregnancy & Parenting

My great aunt had a baby while on the toilet... but then, she had 19 children in total so I'm sure by baby 10 it wasn't that big of a deal.