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 10432 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 91 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 267 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
Just got back from an infant first aid class. Current guidelines (in the USA) now say you should not use any kind of finger sweep (for adults and infants) - it's better to let the body try to clear the obstruction itself. The only time you intervene is when the airway is completely obstructed and they cannot breathe. But the teacher did say it's hard not to step in when you see your baby gagging, so if you really can't stop yourself then use a finger and thumb 'pincer' rather than a single finger sweep (which poses a higher risk of pushing the obstruction further down the throat).
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.
One thing I do now that I wish I had done earlier on (though not sure I could have done in the first 6 months due to brain fog), is if I find myself thinking "I wish I could do X" or "I wish I had time for..." even if it's a fleeting thought, I write it down. Well actually I put it in my toodledo list, which I can access on my phone/computer/wherever. Then when I find time I'm like soooo what do I do again? Oh yeah! I wanted to do this thing! I mean, as simple as "read book" or "bake a thing" or something.
Early on though it might be good to look at the list though. Just add things to it. Eventually it gets better and time will come back.
^This reminded me, we got two receiving blankets that were made for us, and they were bigger than the little ones that people buy. THOSE were way more useful for much longer.
So, my pregnancy hormones are causing me major mood swings right now. I don't necessarily feel ashamed of it, but I'm frustrated enormously by it because I've got a ton of projects at work and a two-year-old to deal with, and I honestly do not have time to sit and cry for 30 minutes every few hours. I really hate being pregnant, for that and other reasons, but right now it's mostly that.
This morning I felt awesome and totally zen and amazing and only vaguely nauseated, and then a couple of things hit at work that I routinely eat for goddamn BREAKFAST and I'm a puddle of tears in my office. Luckily, I work from home so no one can see me, and all I can really do is push through it and keep getting stuff done. But it majorly sucked. Maybe there's no way around it...but if anyone has any ideas for coping with this stuff I'd be grateful. When you Google pregnancy hormones and mood swings the majority of advice is aimed at husbands "surviving" it, which immediately sends me into a rage spiral.
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:
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):
This thread makes me want to make a graph of my excitement levels about other people's pregnancies. It would start off quite mild through teenage years and college, start to spike in early adulthood when I started thinking about maybe being pregnant someday but it was still a distant future possibility, reach a high right around the time my first friends started getting pregnant, drop a little when my husband and I started trying and encountered issues (took us 11 months first time around with my irregular cycles), reach a frenzied crescendo around the time I got pregnant (I was super-excited about being pregnant at the same time as one of my best friends -- we were due with baby girls within a week of each other). Then it dropped like a rock to the depths of deepest despair when our first daughter died at 18w2d in my first pregnancy -- I just couldn't bear to see other pregnant women, especially smug pregnant women who were rubbing their bellies all the time and had the nursery painted by the middle of the second trimester. Now that I'm 36 weeks pregnant with our second, a son, my excitement levels about other people's pregnancies are generally about where they were in teenage/college years, although now tinged with a huge amount of cynicism. Since everyone I know is pregnant at my age, I couldn't care less if someone I know is due within a few weeks of me -- I've been there before. Someone pregnant for the first time and over the moon? I remember feeling that way. It didn't end well. I'm >8 months pregnant, and I still get intensely jealous of first-time pregnant women who have never experienced problems. Heck, I still feel stabs of jealousy when I see other pregnant women rubbing their bellies. I've spent my whole pregnancy mentally keeping my kid at arms' length, not really believing that he's going to be born. I'm still emotional and excited about my pregnancy, but it's all dulled considerably compared to what I felt the first time around -- and I spend much more time worrying and educating myself about potential problems.
I definitely don't like these types of toys. I was so grateful when my brother asked how we felt about electronic toys before purchasing one for our kid. Unfortunately, most people don't ask, and even if they know don't care. Our general policy is to not replace batteries when they die, but we haven't caused any to die myteriously. The only batteries we have in the house are attached to a phone, a laptop, and a couple spares for a flashlight.
Just today I heard about this small
We had something similar happen on the oldest's birthday last year. We had a talk with him about how he was fortunate, and had a lot of things, and asked him to consider sharing with less fortunate kids. He ended up leaving half of them unopened and we took them to the children's hospital.
Thanks everyone! Lots for me to think about...
I have just started prenatal yoga and it seems that it will be pretty useful - although it's way more physical hard work than I expected (I'd better get used to it now, I guess).
Also, I hope I get an inflatable baby from whichever course I end up going with.
It's not at my (US) hospital, alas, and I got the impression it is not common. :-( I am just planning to eat a bunch of yogurt and other probiotic stuff after birth and hope for the best (there's apparently some evidence that good bacteria can be passed through breast milk, so hopefully as I rebuild my own microbiome I'll also be helping my baby to build his). I'm simply not willing to take the risks associate with passing up antibiotics, so I think focusing on rebuilding a healthy microbiome is probably the best I can do.
It's currently -22 C here and didn't get above -18. The wind was pretty bad too, which makes it worse. *shrug* Brisk activity would have been fine, like sledding or skiing, if it hadn't been for the wind, but trying to actually learn things I think would be much more challenging. Not the least of which is it would damage any equipment you were trying to use. I don't think you could really sustainably do it for the entire winter, or at least not for January and February.
^ You'd have to pick something like heavy metal or drum & bass. Your kid would turn out all punk as a result, so it's win-win!
I think your baby totally wins the "disapproving baby" contest. Her face is amazing. She's got the eyebrows and the mouth and oh man.