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 8489 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 80 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 261 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'm bilingual in Russian and English, but I picked up English at the age of 13. Not sure if it made me any smarter, but I do want to give my kid that advantage. My partner and I haven't really talked about how we're going to do it yet, but we do want to do it. If nothing else, he or she will always be able to make some money as a translator. I'm not a professional translator, but back when I was unemployed, I made some nice $$$ translating books.
I'm even thinking of hiring a Chinese-speaking nanny or babysitter, so that the kid will pick up Chinese as well as Russian and English. The kid is still gestating at this point, so we've got some time.
My boobs are small, and this is important for a couple of reasons: At any one time I can only produce a max of about 6 oz.
Actually, the physical size of your boobs doesn't have much to do with how much you produce. There are lots of small-breasted women who produce a lot and lots of large-breasted women who don't. It's mostly genetic and some other variables thrown in (e.g. if there was a lot of BPA in your mom when
You don't have to post at all if you don't want to! But we're here to offer support if you do want to.
This does get a little better over time, when they're a little more autonomous. Though I still long for the day when I can just freaking go to the bathroom all by myself. (I seriously spent like 20 minutes in the bathroom the other day while the hubby was watching the kid @ a birthday party, just for that reason. I mean how sad does that sound?)
Any chance of arranging a tag-team schedule?
Here's a really funny humor bit about sleep, but the same general idea can apply to pretty much any "advice" given to new parents.
https://chimericalcapuchin.wordpress.co ... babybooks/
A Beautiful article by writer Kathryn McDowell recently I read liked to share with you
Why Pocket Diapers Are Better Than Disposables :
As a young parent, you've no doubt heard of pocket diapers. Perhaps a neighbor or a co-worker told you about them. Or it was your babysitter, who asked you to get them soon. Well, so many families in America are today turning to pocket diapers for their little ones. But a majority still holds on to disposable diapers, while being curious about pocket diapers at the same time.
Why are diapers so great? For a start, pocket diapers come with brand new fabrics and super absorbent pads, are easy to put on, simple to take off, easy to wash and quick to dry. And they are better than disposable diapers.
They are Cheaper
Until your child is potty trained, you'd probably spend something close to $2500 to $3000 on diapers - which is quite a lot. Biodegradable disposable diapers are even costlier. But with pocket ones, you won't have to spend anything more than $350 to $400, till your child is potty trained.
I really want one of those baby boxes and would jump at it if not for $69.95 shipping. Will keep thinking about it, I suspect my resolve will crumble eventually.
Bonding with my future infant is a concern of mine, because my depression is debilitating. I'm relieved to know that normally functioning women don't feel that head-over-heels mushy baby love.
Some of my family members who work in the healthcare system have overheard some doozies.
I work in healthcare, so I can relate. I think my favourite was a kid called "Abcde" which we were assured was pronounced "Abasidee". Mirena was a cute choice, named after the contraceptive device. Then there have been some good narrative names including places of birth - e.g. "Shell" (after the baby born in a petrol station carpark) - and places of conception - e.g. "...(a suburb which I'll keep secret - just in case this somehow breaches some poor kid's privacy) bus stop."
Recently found out how much energy it takes to raise a child. Woah.
I'm pretty infuriated that in Canada it can cost $1,676/month for daycare, when science actually tells us we evolved to help each other raise children. I wrote a blog about this in case anyone is interested! I would really like to see this change for mothers all over Canada.
https://textualorientation.wordpress.co ... ledaycare/
First 2 were on purpose, 3rd kinda not so much, 4th was totally an oops (when you think things are broken, they have this habit of fixing themselves). Made sure we were done after that. Aside from that, we knew we'd have at least 2, likely 3, but the timing was not at all what we thought we were "planning". Such is life.
It's alright to discuss these topics, but there needs to be boundaries. I would use the following, personally:
1. Don't insert yourself into a stranger's situation or bring up the topic yourself to a stranger.
2. It's probably not your business if you're not a parent yourself.
3. Ask the person why they are making these choices, don't assume.
4. Try to end on a positive note.
I don't feel right bringing up to my sister that I don't agree that she spanks my nephew, but after being a teacher, I am pretty forgiving of parents' choices. It's the hardest role there is. Even though I want to raise my children on nutritious meals, cloth diapers, and museum passes, I know I'm going to slip up and give them fries, Huggies, and Disney DVD's.
I also feel that home birth is a fine option for low-risk births, where the mother is well coached and the midwife is reputable. If you live near a hospital and your midwife is highly qualified, why not? They have equipment. I won't be choosing this option, but with any birth plan there needs to be a series of precautions taken.
Probably not. As we pointed out in the other topic, 34 weeks isn't even on the chart because it's so rare:
You'd be better off worrying over a car accident.
I will do cheers but in people's experiences and options I should be ok