Do babies come on their due dates?
This was the question on my mind during the later stages on my pregnancy in the spring of 2010. I heard a lot of conflicting information about what a "due date" meant and when babies were born. Some people saw the "due date" like a deadline... if the baby hasn't arrived yet, it's late, it's time to freak out. Some people said due dates were a bad example of western intervention, used by doctors as an excuse to cut us all open. Some people said that first time moms should expect to go late, it's normal and you should chill out. I found some scattered statistics about what week babies came... and a lot of those graphs just said "X% were born at 40 weeks" but didn't explain what that meant (during the 40th week of pregnancy? 40 weeks accomplished? On day 280?). And trust me if you're pregnant, you start counting DAYS when that time comes around. There is a huge difference between 40 weeks 0 days and 40 weeks 5 days.
I was unable to find great data that satisfied me. So, armed, with a website, I started running a simple survey about due dates. If you've had a baby, please take it!
So far the survey has had 7932 participants, and I've put together these pages of charts that show interesting things I've learned from the results. I am not a mathematician, so there's no in-depth statistical analysis. I'm an engineer, web programmer, and (as of 2010) mom. When I started the survey I was just a very very pregnant woman wondering when my baby was going to show up.
Here's the very basic "who took the survey" plot. More charts with different information are listed at the bottom of the page.
I was unable to find daily breakdowns of when births occur, but there have been other studies about due date accuracy. I think the data is hard to find because the medical community has accepted the fact that it's impossible to exactly predict when a baby will show up, so they're okay with just knowing about when it happens, and us pregnant women are also urged to be okay with just knowing about when it will happen. But if you're a geek like me who loves statistics, that's tough.
All these studies describe the length of pregnancy in days. For reference, 280 days = 40 weeks = 9 months 6 days.
The length of human pregnancy as calculated by ultrasonographic measurement of the fetal biparietal diameter (H. Kieler, O. Axelsson, S. Nilsson, U. Waldenströ) has a very nice table of 10 published studies, which found various means between 272-283 days. The authors contribute their own results as well, recording over 800 mothers who went into labor spontaneously. When pregnancy length was calculated using ultrasound in the second trimester the mean was 280.6 days, standard deviation 9.7 days. When it was calculated using LMP, the mean was 283.6 days with a standard deviation of 10.5 days.
A study from the Swedish birth registry involving 427,582 singleton pregnancies the mean, median and modal durations of pregnancies were 281, 282 and 283 days respectively. The standard deviation was 13 days. This study did not consider whether labor was medically induced or not. (Duration of human singleton pregnancy—a population-based study, Bergsjφ P, Denman DW, Hoffman HJ, Meirik O.)
A 1999 study of over 17,000 spontaneous deliveries stated that due dates are more accurate if we add 282 days to LMP instead of 280 (Evaluation of ultrasound-estimated date of delivery in 17,450 spontaneous singleton births: do we need to modify Naegele's rule? Nguyen TH, Larsen T, Engholm G, Møller H.)
A 2003 London-based study of over 122,000 pregnancies with spontaneous onset of labor (except they call it "labour" because, well, you know) found that average gestational age at delivery was 40 weeks for white Europeans but only 39 weeks for members of the black and asian ethnic groups. I chose not to ask for ethnicity or race in my survey because it's so hard to define, so many people are a combination of races, but the study is interesting. Another note: it was made up entirely of first time ("nulliparous") mothers. (International Journal of Epidemiology 2003;33:107–113 Roshni R Patel,Philip Steer,Pat Doyle,Mark P Littleand Paul Elliott)
And finally there's this 1990 Harvard study called The length of uncomplicated human gestation (Mittendorf et al). The study looked at 31 first-time moms at one private practice to conclude that their average due date was eight days early. That's not a very big sample size, which I think is why it's the only study that found 288 days as the median. I really wish people would stop bringing it up, but it seems to be popular so I'll just say if you want to read it and come to your own conclusions, it's here.
Come on people, if 288 days was really the median that means that more than half of all pregnancies would end past 41 weeks... seems like we would have noticed something like that by now.
There is good weekly data from the CDC that talks about birthweight and weight gain and inductions and all kinds of good stuff. But it's not the daily breakdown I wanted, and it doesn't break down weekly stats by whether the births were spontaneous or induced.
It became apparent to me by reading studies that no matter what factor people added into consideration, it was still impossible to predict the start of labor. Even IVF patients, who know the HOUR their baby was created, don't get accurate due dates. So I see no point in taking all these factors into consideration, if it's going to be a range of dates lets just all throw whatever randomness we have into the pot and see what the range is. Several studies and my survey have found that there's a standard deviation of over a week... this makes the bell curve pretty flat on top. Moving a due date a day up or back based on ovulation really makes no difference because all the dates around 40W are almost equal in terms of your probability of going into labor.
Science wasn't really my goal. By that I mean I'm not terribly interested in how the human body works... I'm interested in how life is for women like me. The women who are reading this and visiting my website are mostly internet users from english-speaking countries... well, so are my survey participants. I see that as a good thing.
That said, even if it's not scientific the fact that the results are matching real scientific studies mean that I must be doing something right. The studies mentioned a few paragraphs above here seem to support the fact that the 280 day mean, 9-10 day standard deviation is the norm... well that's what my results show too. I think if the big numbers about the curves are correct than the little details are likely to be correct also.
Twin births make things slightly out of the norm, so they are not included in the chart. This excludes 74 results. I didn't really ask good survey questions for twins anyway. If you are pregnant with twins and looking for data, there's a good survey going over here.
In addition, around 200 results I started noticing a big spike in the number of babies born on their due date. I believe this is because women who have their babies on their due dates are more likely to remember it, and be enthusiastic about taking a survey. To account for this I've capped the number of results shown at exactly 40 W, and 242 results are excluded.
Due Date Survey DataDue 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?
Survey input dates
More ResourcesPregnancy Day-by-Day
Fast pregnancy calendar
Baby age calendar
EDD Icon Generator
Jo's Birth Story
Weeks vs. Months Explained
Charts generated by flot
I think it's easy to say rioting in the streets is a bad idea when it's not an issue impacting me. I can't think of any 'good' way to express the anger and frustration that is building around black people being killed and it being shrugged off. Young people are dying and it's upsetting, I can't condemn anyone for taking to the streets to express that.
I am disappointed by the number of people taking advantage of the situation and using it to loot the city.
6) peanut butter: I read that the link is not likely, but that if you have excema, asthma, or allergies, it might be more likely that consuming peanut butter could lead to this allergy. Unfortunately, I have all three, so have stopped peanut butter but did buy some almond butter, hopefully that is okay.
When I was little I remember getting a few toys. My parents didn't have that much money (I learned later), but even getting a few things (some clothes, a bucket of duplos) was plenty. The family gifts were the big ones - things like a computer (OMG a Commodore 128) and two very nice sleds.
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.
I think the only one of these I've seen is Juno. It was a good movie but I'm not sure it counts as my favorite if it's the only one I've seen?
zomg, this whole forum is worth it if we get more people exposed to SAVED!
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 ...).
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.
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.
Sometimes I try to see whether the film and the book each stand on their own. If they both do, I don't worry as much about which is better.
When I like the book more: usually it has to do with being so in love with the worldcraft and the descriptions of the book that the film can be entertaining and even moving but just doesn't have the form to develop those things I otherwise loved. See LOTR books (loooove) v. films (love). Sometimes the books are just better, usually because they're in the hands of an author much better than anything the film produced - see Fantastic Voyage by Isaac Asimov, or Dune compared even to David Lynch's version, or the ill-fated attempt to make an Earthsea miniseries.
When I like the film more: when there's something to the film that is brilliant and well-done in its own light. If I come away from the film really liking it, and think the book adds some things but isn't necessary, I like the film more. I'm thinking of Howl's Moving Castle as a good example, since I like the books but love even more its combination with Miyazaki's animation style and storytelling. This also goes for a lot of films that are novelized, like Star Wars. And sorry to the book The Princess Bride, but the film is the first to come to mind.
welcome new folks and thanks for commenting, I'm optimistic!
I find there is a lot of misinformation out there, or information that is jumping at safety without evidence (my pregnancy app recently told me that to be safe, I should limit computer/phone use throughout).
good lord. if computer/phone use was bad for babies mine would have come out as horseshoe crabs or something.
First, humor me a bit. You see the word code-meshing. What do you think of?
Source code integration! Especially where you have different developers working on the same bit of code and you have to be careful to accept the right combination of changes ... (it's really called merging, I think).
I've been long-winded enough. What are your thoughts? Are there places where you have noticed code-meshing in action?
Can I count times when I accidentally use a kiwi (i.e. New Zealand English) word in my otherwise-British-English without realising it? Since NZ english is so close to standard British English I definitely used to have a blind spot for words (like 'jandal', i.e. what you would probably call a flip-flop in the UK - a sandal with a toe post between the big toe and second toe and a strap either side) which were distinctively kiwi, or had a different meaning (e.g. 'togs' in NZ means 'swimming costume' whereas in the UK it means 'clothes').
really you guys? I unfriend all the time!
why mute someone? that means they're still going to be seeing your posts, commenting on your photos, getting to be "in" your life, and never know anything changed. what good is happening by keeping them around?
My former art teacher is quite conservative, but I still like his comments on my artwork.
I put people I think are otherwise perfectly delightful on mute because they flood facebook with useless crap. I don't want them to get the idea that I hate them, but I don't feel like seeing pages of what they have to say.
I think a lot of people have opinions I don't care for. Rather than offending someone I know and respect in person, I choose to just not see it. Facebook has a knack for showing sides of people I don't want to see, but it's just small sides of them. To me, it's not worth shutting out the person completely. After awhile, I occasionally take them off mute to see if they stopped with their nonsense.
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