Average day of spontaneous labor vs. age of mother at time of birth

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I read somewhere that maternal age has something to do with when labor sets in, so I included it in the survey. I found nothing terribly interesting or conclusive.

This sort of validated my decision to keep the survey simple and not consider every little thing in the world that people are curious about. Could the average day change depending on your age, ethnicity, whether you were on the pill, country of origin, etc? Maybe. But we're talking about something where with a standard deviation of over a week here... about the same number of people give birth on day 279 as on day 287. So if some random thing changes the average by 2 days will that knowledge help make your due date any more accurate? I'm thinking no.


Data table - Average lenth of pregnancy per age

Age# of participantsAverage day of spontaneous laborAverage day including ± 1 year of age
12 1 29041W,3D27739W,4D
12.5 1 28741W,0D27739W,4D
13 2 26437W,5D27339W,0D
13.5 1 28340W,3D27038W,4D
14 2 27739W,4D27339W,0D
14.5 3 26337W,4D27339W,0D
15 12 26738W,1D27439W,1D
15.5 15 27939W,6D27539W,2D
16 28 27439W,1D27639W,3D
16.5 32 27639W,3D27539W,2D
17 75 27639W,3D27639W,3D
17.5 60 27739W,4D27639W,3D
18 72 27339W,0D27639W,3D
18.5 86 27639W,3D27639W,3D
19 114 27639W,3D27639W,3D
19.5 120 27639W,3D27639W,3D
20 131 27639W,3D27639W,3D
20.5 170 27639W,3D27639W,3D
21 171 27739W,4D27639W,3D
21.5 163 27739W,4D27639W,3D
22 191 27739W,4D27739W,4D
22.5 176 27639W,3D27739W,4D
23 193 27639W,3D27739W,4D
23.5 194 27839W,5D27739W,4D
24 183 27939W,6D27739W,4D
24.5 218 27639W,3D27739W,4D
25 212 27739W,4D27839W,5D
25.5 208 27939W,6D27839W,5D
26 226 27739W,4D27839W,5D
26.5 240 27839W,5D27839W,5D
27 287 27839W,5D27839W,5D
27.5 293 27939W,6D27839W,5D
28 282 27939W,6D27839W,5D
28.5 289 27839W,5D27939W,6D
29 316 27939W,6D27939W,6D
29.5 315 27939W,6D27939W,6D
30 293 27939W,6D27939W,6D
30.5 310 27839W,5D27939W,6D
31 301 27939W,6D27939W,6D
31.5 239 28040W,0D27939W,6D
32 254 28040W,0D27939W,6D
32.5 250 28040W,0D28040W,0D
33 216 28040W,0D28040W,0D
33.5 182 28040W,0D28040W,0D
34 186 27939W,6D28040W,0D
34.5 147 27839W,5D28040W,0D
35 105 28040W,0D28040W,0D
35.5 93 28140W,1D28040W,0D
36 79 28040W,0D28040W,0D
36.5 80 28040W,0D28040W,0D
37 62 28240W,2D28040W,0D
37.5 55 27939W,6D28040W,0D
38 62 27839W,5D28040W,0D
38.5 52 28040W,0D28040W,0D
39 40 28140W,1D28040W,0D
39.5 41 28040W,0D28040W,0D
40 37 28140W,1D28040W,0D
40.5 26 28140W,1D28040W,0D
41 52 27939W,6D27939W,6D
41.5 49 27939W,6D27939W,6D
42 36 27839W,5D27939W,6D
42.5 25 27839W,5D27839W,5D
43 31 27939W,6D27839W,5D
43.5 21 27739W,4D27839W,5D
44 13 27439W,1D27839W,5D
44.5 18 28140W,1D27839W,5D
45 10 28140W,1D27839W,5D
45.5 12 27539W,2D27839W,5D
46 1 28640W,6D27939W,6D

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

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Recent Comments

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Academic redshirting

Wed Nov 9 9:54 PM by Sonic# in Pregnancy & Parenting

^ To your final question, maybe that would be true to some extent. But that makes me ask a different question:
to what extent is redshirting necessary because of the relative age of any members of a class (like, whether you're the *youngest* or the *oldest*) and to what extent is it necessary because of their absolute age (not yet being 5 and therefore being more likely to be developmentally behind on average)?

Because if it's more the latter, then redshirting everyone born in September would just mean that kids are, on average, one month developmentally ahead entering kindergarten. The difference in their maturity might matter less if they meet a baseline for maturity. But if it's more the former, then the hockey metaphor comes into play, with younger kids perhaps still getting less "play" in class.

And I could easily see it being both: those kids might have slightly lesser disadvantages, but some disadvantages would remain.


kids' obsessions

Sat Oct 15 8:08 PM by melsbells in Pregnancy & Parenting

I could see saunas becoming an obsession for a number of very social reasons as well, depending on your family's sauna practices. I honestly can't think of any common themes or rituals shared by all branches of my U.S. family, other than like eating together, but that seems too banal(/essential for survival) to really become an obsession. My Finnish family, on the other hand, all sauna as a social ritual. Whether or not you allow your kid in saunas yet, if there's a lot of exposure to the ritual, they could probably pick up on the social importance. It might make sense that kids are probably wired to pick up on things that the adults in their life think are important (**not a child psychologist**).
<...> I know I was super into the instant evaporation of water and associated *hissssss* the first time I was in a sauna at like age seven.
This is an excellent point. And although I know they exist, I haven't encountered any Finns who don't like sauna. There are a lot of steps to it. The kid gets to help their grandfather build the fire when we're together, knows that wood burning saunas are better than electric saunas, and absolutely loves the sound of the water hitting the hot stones. I can't imitate the sound as well as the kid does.


bringing children up naturist

Sat Sep 24 1:18 AM by filmmakingally in Pregnancy & Parenting

It's about teaching children to make love so that they do it themselves. Love has no age or genetic requirement. It's healthy for young siblings to make love, and it's unhealthy if they don't. Sexual repression of children fucks them up as adults. Because the parents are secretive about it, children get the idea that it's bad, which starts the process of sexual repression.

Gross. Yuck. Eww. I've run out of ways to express how disgusted I am with what you've said here. Ewwwwwww!!!!!!!

No, siblings should not make love. It is in our genetic interest that we don't do this. Ever. This is a cultural universal.


Middle grade / Beginning Chapter Books

Fri Sep 9 8:01 PM by melsbells in Pregnancy & Parenting

I think a big driver in getting them to read is to find stories that they like.
Definitely this. I once tutored a kid who had been held back twice in elementary school and was still a couple grade levels behind on reading skills. He was given a book from the Captain Underpants series because it was supposed to be at his reading level but he thought it was utterly stupid. I don't think we ever found books that both matched his reading level and maturity level, but once we started reading books better suited to his interests, it didn't matter that they were more difficult.

One of my cousins kids read the Warriors series and was really into it. She was bulllied in school, but I don't think it was instigated by her reading choices.

I don't know any recent books for this age group but I've heard great things about the Adventure Time comics.


Carriers vs Ring Sling

Mon Sep 5 8:59 PM by melsbells in Pregnancy & Parenting

^That's funny because the bjorn carrier is the one I was given that I didn't like. I think that just re-emphasizes that the same thing isn't going to work the same for everyone.


development balalnce

Wed Nov 9 9:12 PM by melsbells in Pregnancy & Parenting

It's a great point that the scales often tip in different directions at different times. I can see how I could provide opportunities for the first four categories, but how does someone go about encouraging gross motor skills? I was under the impression that out of all development, that one was sort of automatic, like physical growth.


Sleep Training for Parents and Infants

Sat Oct 1 9:34 PM by antfancier in Pregnancy & Parenting

Thank you! I'm currently stuck under 20lbs of sleeping baby because all day time naps have to be in my arms or they don't happen.


Don't give your kids antidepressants.

Thu Sep 15 9:13 PM by Nachos in Pregnancy & Parenting

Mental health issues will never start to hurt, therefore no preemptive treatment is needed.

Mental health issues hurt, take it from me. There are many psychosomatic disorders out there which affect your body even though the real problem is in your mind. But to get better, you HAVE to treat both. Pre-emptive treatment also can stop some disorders from becoming too bad. And yes, sometimes drugs can be very very helpful.

I don't think you know what you're talking about and all this "I know because of divine intuition" bullshit is starting to piss me off. if you ask others for sources, be kind enough to provide some yourself.

If this thread continues to be shit-slinging, I will lock it.


Denial Trends?

Thu Jul 21 7:24 PM by SameMom in Pregnancy & Parenting

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. :)


Parents Warned they Could Lose Custody of Fourteen-Year-Old Over This

Mon Nov 7 3:33 AM by garbage videos in Pregnancy & Parenting

It is wrong to lock horses in cages and breed them as if they are slaves.
I sincerely hope that you aren't condoning slavery with that implication that it isn't wrong to keep humans in cages and force them to "breed". It's probably just an unfortunate word choice.
I said it is wrong to put horses in cages and breed them as slaves. So I don't know how you read things. Frankly you are irritating me because I shouldn't have to explain how I said 2+2=4 when you are accusing me of saying 2+2=5. In this age people should have mastered how to read clearly and I shouldn't have to micromanage my text and clear what I have already layed out clearly for you.

To be fair, if the girl is a Female to Male transsexual, her hormones are not so important, at an old age Male hormones will mutate her body and have the same effect. But with boy's its more tragic and serious. Boys who want to be girls, must stop their toxic T at an early age, or else their face will be permanently ugly and bony


Cry it out vs. Attachment

Mon Sep 26 12:12 AM by lyra211 in Pregnancy & Parenting

We sort of went middle-of-the-road. In the beginning, we had the sidecar cosleeper, and that worked great. Baby woke up a lot at night because he was a newborn, but I could pick him up, feed him, and put him back down without getting out of bed. He seemed to pretty much only be waking up if he was hungry, and settled pretty well after that, so all was good with the world (yes, there were nights when we'd have to get up and bounce on the yoga ball for a while, but we never had the horrific newborn nights that we seem to hear about where he was inconsolable at 2am). He started sleeping longer stretches and was sleeping one 8-9 hour stretch per night by the time he was two months old.

Around 3 months as he started getting more sensitive to noise, our nighttime rustlings would wake him up -- and if it wasn't my husband or me rustling it was the dog, who also sleeps in our room. It got to the point where I was so worried about someone waking him up that if I heard anyone moving in the night I'd instantly be alert and ready to murder someone if the baby woke up, and then even if the baby didn't wake up I was all keyed up and would have trouble falling back asleep. So for about a month, I moved myself to the floor of the baby's room. He transitioned easily into the crib, but I slept on the floor of his room every night and fed him when he woke up hungry.


learning to use a toilet

Sun Sep 11 2:33 PM by Angelica in Pregnancy & Parenting

My statement was meant to indicate that I'm not finished with my thoughts on this topic, rather than to create drama.

I believe parents in this world universally make a big mistake when it comes time to start thinking about their children using the toilet. Kids feel forced to do it, and this breeds resentment and damages their self-esteem. Having the father (the mother is needed in the battle against the patriarchy) stay home with the children and homeschool them while they haven't yet decided to train themselves is the way to avoid humiliation by their more-repressed peers.

I would also like to point out that limiting elimination to the toilet at any age creates situations where the person's health is compromised due to the lack of availability of a bathroom. In these situations, I strongly advise parents to let their children wear diapers no matter their age. Retention can lead to kidney stones, intestinal damage, urinary tract infections and harmful bacteria and toxins in the bloodstream.


How to Announce Baby #4?

Thu Sep 8 5:00 AM by Carol Palmer in Pregnancy & Parenting

FB pic is the best idea. All your friends and relatives can definitely post in comments or expressions . Consider yourself lucky to have many children. They are a blessing from God


Public Service Announcement: Furniture Anchors!

Fri Jul 1 5:17 AM by cwbyrvr in Pregnancy & Parenting

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%.