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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
14 1 27339W,0D27539W,2D
14.5 3 27439W,1D27539W,2D
15 6 26838W,2D27639W,3D
15.5 13 27839W,5D27539W,2D
16 13 27639W,3D27639W,3D
16.5 11 27939W,6D27539W,2D
17 27 27439W,1D27539W,2D
17.5 30 27639W,3D27639W,3D
18 35 27339W,0D27639W,3D
18.5 50 27639W,3D27639W,3D
19 60 27839W,5D27739W,4D
19.5 54 27739W,4D27739W,4D
20 61 27939W,6D27739W,4D
20.5 82 27639W,3D27739W,4D
21 91 27639W,3D27739W,4D
21.5 88 27739W,4D27739W,4D
22 110 27739W,4D27739W,4D
22.5 108 27839W,5D27739W,4D
23 106 27539W,2D27739W,4D
23.5 100 27739W,4D27739W,4D
24 108 27839W,5D27739W,4D
24.5 113 27639W,3D27739W,4D
25 112 27639W,3D27739W,4D
25.5 123 27939W,6D27739W,4D
26 114 27739W,4D27739W,4D
26.5 129 27739W,4D27839W,5D
27 165 27739W,4D27839W,5D
27.5 177 27939W,6D27839W,5D
28 152 27939W,6D27839W,5D
28.5 163 27839W,5D27839W,5D
29 168 27839W,5D27839W,5D
29.5 164 27939W,6D27839W,5D
30 160 27939W,6D27839W,5D
30.5 166 27839W,5D27939W,6D
31 152 27839W,5D27939W,6D
31.5 131 28040W,0D27939W,6D
32 123 28040W,0D27939W,6D
32.5 135 27939W,6D27939W,6D
33 112 28040W,0D27939W,6D
33.5 94 27939W,6D27939W,6D
34 111 27939W,6D28040W,0D
34.5 68 28040W,0D28040W,0D
35 48 28040W,0D28040W,0D
35.5 58 28140W,1D28040W,0D
36 51 28140W,1D28140W,1D
36.5 39 27939W,6D28140W,1D
37 40 28340W,3D28140W,1D
37.5 36 28040W,0D28140W,1D
38 42 28040W,0D28040W,0D
38.5 32 28040W,0D28140W,1D
39 32 28240W,2D28040W,0D
39.5 26 28040W,0D28040W,0D
40 27 28140W,1D28040W,0D
40.5 17 28140W,1D27939W,6D
41 41 27839W,5D27939W,6D
41.5 33 27839W,5D27939W,6D
42 22 27839W,5D27839W,5D
42.5 9 28140W,1D27839W,5D
43 19 27839W,5D27839W,5D
43.5 5 27138W,5D27839W,5D
44 5 27539W,2D27839W,5D
44.5 5 27739W,4D27739W,4D
45 1 29341W,6D27639W,3D
45.5 1 27939W,6D27839W,5D

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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