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 11359 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.
This first intro page is all about the methods used and why I think it's valid. If you don't care about the background, just want to see the dang averages, skip to this page or pick one of these:Due date statistics: A study on the length of pregnancy
For reference, here's the very basic plot of who took the survey:
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 95 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 282 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
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
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.
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.
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.
Are boil bags safe to use? Do you use them? Can anyone share some recipes? I'd like to try them but don't know what to cook.
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%.
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?
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.
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.
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.
Don't be silly monk, everyone knows a good conglomerate goes better with milk
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.
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.
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.