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

[ Survey Results Intro | All Charts | Take the survey ]

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,4D27238W,6D
14.5 3 26337W,4D27339W,0D
15 17 26838W,2D27439W,1D
15.5 21 27639W,3D27539W,2D
16 35 27439W,1D27539W,2D
16.5 39 27539W,2D27539W,2D
17 86 27639W,3D27639W,3D
17.5 73 27739W,4D27639W,3D
18 91 27439W,1D27639W,3D
18.5 120 27639W,3D27639W,3D
19 157 27639W,3D27639W,3D
19.5 159 27639W,3D27639W,3D
20 169 27639W,3D27639W,3D
20.5 199 27639W,3D27639W,3D
21 228 27739W,4D27639W,3D
21.5 201 27639W,3D27639W,3D
22 221 27639W,3D27739W,4D
22.5 230 27739W,4D27739W,4D
23 246 27639W,3D27739W,4D
23.5 233 27739W,4D27739W,4D
24 229 27939W,6D27739W,4D
24.5 290 27739W,4D27739W,4D
25 264 27739W,4D27839W,5D
25.5 267 27939W,6D27839W,5D
26 302 27739W,4D27839W,5D
26.5 329 27839W,5D27839W,5D
27 365 27839W,5D27839W,5D
27.5 362 27939W,6D27839W,5D
28 371 27939W,6D27939W,6D
28.5 392 27939W,6D27939W,6D
29 421 27939W,6D27939W,6D
29.5 408 27939W,6D27939W,6D
30 385 27939W,6D27939W,6D
30.5 405 27839W,5D27939W,6D
31 410 27939W,6D27939W,6D
31.5 355 28040W,0D27939W,6D
32 334 27939W,6D27939W,6D
32.5 338 28040W,0D28040W,0D
33 320 28040W,0D28040W,0D
33.5 261 28040W,0D28040W,0D
34 257 27939W,6D28040W,0D
34.5 196 27939W,6D28040W,0D
35 161 28040W,0D28040W,0D
35.5 145 28040W,0D28040W,0D
36 108 28040W,0D28040W,0D
36.5 104 28040W,0D28040W,0D
37 83 28140W,1D28040W,0D
37.5 68 27939W,6D28040W,0D
38 82 27939W,6D28040W,0D
38.5 70 28040W,0D28040W,0D
39 52 27939W,6D27939W,6D
39.5 44 28040W,0D27939W,6D
40 44 27939W,6D27939W,6D
40.5 32 28040W,0D27939W,6D
41 59 27939W,6D27939W,6D
41.5 52 27839W,5D27939W,6D
42 44 27939W,6D27939W,6D
42.5 30 27939W,6D27839W,5D
43 38 27839W,5D27939W,6D
43.5 25 27839W,5D27939W,6D
44 16 27639W,3D27839W,5D
44.5 22 28240W,2D27839W,5D
45 15 28040W,0D27939W,6D
45.5 19 27639W,3D27939W,6D
46 4 28440W,4D28040W,0D

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?
Download the data
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
spacefem.com
spacefem@spacefem.com