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Length of pregnancy for first time vs. second & third time moms

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Cumulative Distribution

This graph shows the percentage of births that'd occured on or before a given day, like a running total.

There's a popular rumor out there that first time moms are very likely to go past their due dates... sometimes even way past. I had people tell me to expect to go a week overdue. Here's what I found in the survey. Considering only births resulting from spontaneous labor:

So why the rumor about first time moms going late? There are articles all over the web that say the average first time mother goes eight days overdue and doesn't have her baby until 41 weeks, 1 day. I say hold off, people. There's only one study that suggested this median: The length of uncomplicated human gestation (Mittendorf et al). The study was simply a record of a few hundred women at one private practice. Only 31 of those women were first time mothers. The study itself calls for further research. You can read it here. Given the small sample size and drastic deviation from the large-scale studies cited in my introduction, I'd suggest we dispell the rumor a bit and calm everybody down. And teach bloggers to read medical studies. Due date statistics are much better looked at as an epidemiology topic than a medical one, anyway.

Average length of pregnancy, by number of subsequent previous births

# of previous births# of birthsAverage Arrival
0434739W,5D
1124239W,5D
29139W,0D

Daily probabilities of spontaneous labor, by number of subsequent previous births

Day 0 previous births 1 previous birth 2 or more previous births
#% #% #%
245 8 0.2 1 0.1 1 1.1
246 12 0.3 0 0 3 3.3
247 3 0.1 3 0.2 1 1.1
248 13 0.3 3 0.2 1 1.1
249 7 0.2 3 0.2 1 1.1
250 11 0.3 1 0.1 1 1.1
251 9 0.2 3 0.2 1 1.1
252 18 0.4 6 0.5 0 0
253 17 0.4 2 0.2 0 0
254 14 0.3 8 0.6 1 1.1
255 25 0.6 4 0.3 2 2.2
256 14 0.3 7 0.6 1 1.1
257 13 0.3 11 0.9 1 1.1
258 22 0.5 2 0.2 2 2.2
259 28 0.6 12 1 1 1.1
260 31 0.7 6 0.5 1 1.1
261 27 0.6 6 0.5 4 4.4
262 55 1.3 6 0.5 3 3.3
263 49 1.1 14 1.1 2 2.2
264 38 0.9 15 1.2 2 2.2
265 62 1.4 18 1.4 2 2.2
266 59 1.4 20 1.6 2 2.2
267 66 1.5 17 1.4 1 1.1
268 54 1.2 18 1.4 2 2.2
269 87 2 27 2.2 5 5.5
270 108 2.5 30 2.4 1 1.1
271 94 2.2 30 2.4 1 1.1
272 111 2.6 43 3.5 2 2.2
273 133 3.1 39 3.1 2 2.2
274 132 3 28 2.3 1 1.1
275 128 2.9 37 3 4 4.4
276 157 3.6 59 4.8 3 3.3
277 175 4 54 4.3 1 1.1
278 185 4.3 51 4.1 1 1.1
279 224 5.2 52 4.2 1 1.1
280 217 5 64 5.2 1 1.1
281 234 5.4 51 4.1 1 1.1
282 187 4.3 69 5.6 1 1.1
283 205 4.7 49 3.9 3 3.3
284 186 4.3 39 3.1 2 2.2
285 184 4.2 48 3.9 1 1.1
286 174 4 63 5.1 3 3.3
287 174 4 55 4.4 1 1.1
288 124 2.9 30 2.4 1 1.1
289 103 2.4 33 2.7 1 1.1
290 91 2.1 36 2.9 1 1.1
291 89 2 11 0.9 1 1.1
292 50 1.2 25 2 2 2.2
293 53 1.2 7 0.6 1 1.1
294 34 0.8 11 0.9 7 7.7
295 10 0.2 7 0.6 1 1.1
296 15 0.3 4 0.3 2 2.2
297 8 0.2 1 0.1 1 1.1
298 5 0.1 2 0.2 1 1.1
299 5 0.1 0 0 1 1.1
300 2 0 0 0 0 0

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.

Bilingual Babies

Mon Mar 2 7:38 PM by Nachos in Pregnancy & Parenting

I am/was a bilingual kid. I am now a bilingual (in another language though) adult. My mother is Dutch and I was born in England so I grew up speaking and understanding English and Dutch. I don't believe I had any problems up until my first day at school when apparently I came home saying "I don't want to speak that funny language any more!" and since my mother was told my doctors and teachers to only speak one language to your kid, I ended up forgetting it all.

Later on (when I was 11) we ended up moving to a Dutch speaking country and even though I was immersed in school I had to learn it all over again. Funnily enough, after about 7 months something clicked and the language started to come back.

Next problem was then we moved to Germany and even though the languages are similar, they are not the same. It took me about three years (immersed again) while learning German too for something to click and I started to also dream in German.

My Dutch teacher in the Dutch country had a grandson who spoke 4 languages fluently at the age of 6. He could differentiate between them too.


Breastfeeding & accoutrements thereof

Thu Feb 26 5:28 PM by rowan in Pregnancy & Parenting

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 were in utero can affect it, we're finding out).


Keeping your pre-pregnancy/parenthood identity

Thu Jan 29 4:36 PM by rowan in Pregnancy & Parenting

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.

I have very little time sans baby anymore
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?)

I know he requires more alone time than I do, and I know he isn't getting any more than I am.
Any chance of arranging a tag-team schedule?


sleep humor

Fri Jan 23 7:13 PM by rowan in Pregnancy & Parenting

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.

"I bought all the top books on baby sleep and development. I read through them all, as well as several blogs and sleep websites. I gathered lots of advice:"

https://chimericalcapuchin.wordpress.co ... babybooks/


Why Pocket Diapers Are Better Than Disposables

Sun Jan 11 3:31 PM by Nancy Erick in Pregnancy & Parenting

Hi everyone

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.


10 things you can leave off the baby registry

Sat Feb 28 7:48 AM by Gnarlbanya in Pregnancy & Parenting

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

Fri Feb 6 4:35 AM by Zeph in Pregnancy & Parenting

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.


name trends

Wed Jan 28 8:58 AM by Lemon in Pregnancy & Parenting

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."


It takes 13 million calories to raise a child!

Wed Jan 21 4:32 AM by textualorientation in Pregnancy & Parenting

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/


some quotes recently I read

Sat Jan 10 4:50 PM by Nancy Erick in Pregnancy & Parenting

i search about these quotes in google


How did you decide how many kids to have?

Fri Feb 27 2:42 AM by MFS in Pregnancy & Parenting

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.


Because judging other parents is absurd.

Tue Feb 3 7:05 AM by Zeph in Pregnancy & Parenting

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.


34 Weeks

Fri Jan 23 11:57 PM by Sonic# in Pregnancy & Parenting

Probably not. As we pointed out in the other topic, 34 weeks isn't even on the chart because it's so rare:
http://spacefem.com/pregnant/charts/duedate1.php

You'd be better off worrying over a car accident.


Work

Thu Jan 15 9:17 PM by bigdaddy in Pregnancy & Parenting

I will do cheers but in people's experiences and options I should be ok


Working as due date approaches

Mon Jan 5 6:18 AM by Bork in Pregnancy & Parenting

However long you end up staying at work, once you're in labor, PLEASE GO HOME. Or to the hospital. Because staying at work while you're in labor is hella awkward for everyone involved.