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

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 participants	Average day of spontaneous labor		Average day including ± 1 year of age
16	20	274	39W,1D	276	39W,3D
16.5	40	275	39W,2D	276	39W,3D
17	90	277	39W,4D	276	39W,3D
17.5	74	277	39W,4D	276	39W,3D
18	100	274	39W,1D	276	39W,3D
18.5	123	276	39W,3D	276	39W,3D
19	170	276	39W,3D	276	39W,3D
19.5	168	276	39W,3D	276	39W,3D
20	179	276	39W,3D	276	39W,3D
20.5	211	276	39W,3D	276	39W,3D
21	235	277	39W,4D	276	39W,3D
21.5	215	276	39W,3D	276	39W,3D
22	228	276	39W,3D	276	39W,3D
22.5	239	277	39W,4D	277	39W,4D
23	253	276	39W,3D	277	39W,4D
23.5	239	277	39W,4D	277	39W,4D
24	243	279	39W,6D	277	39W,4D
24.5	306	277	39W,4D	277	39W,4D
25	277	277	39W,4D	278	39W,5D
25.5	279	279	39W,6D	278	39W,5D
26	315	277	39W,4D	278	39W,5D
26.5	346	278	39W,5D	278	39W,5D
27	386	278	39W,5D	278	39W,5D
27.5	369	279	39W,6D	278	39W,5D
28	384	279	39W,6D	279	39W,6D
28.5	407	279	39W,6D	279	39W,6D
29	439	279	39W,6D	279	39W,6D
29.5	422	279	39W,6D	279	39W,6D
30	413	279	39W,6D	279	39W,6D
30.5	430	278	39W,5D	279	39W,6D
31	424	279	39W,6D	279	39W,6D
31.5	371	280	40W,0D	279	39W,6D
32	353	279	39W,6D	279	39W,6D
32.5	364	280	40W,0D	280	40W,0D
33	336	279	39W,6D	280	40W,0D
33.5	274	280	40W,0D	280	40W,0D
34	274	279	39W,6D	280	40W,0D
34.5	203	279	39W,6D	280	40W,0D
35	170	280	40W,0D	280	40W,0D
35.5	162	281	40W,1D	280	40W,0D
36	115	280	40W,0D	280	40W,0D
36.5	108	280	40W,0D	280	40W,0D
37	86	281	40W,1D	280	40W,0D
37.5	72	279	39W,6D	280	40W,0D
38	84	278	39W,5D	280	40W,0D
38.5	71	280	40W,0D	279	39W,6D
39	53	279	39W,6D	279	39W,6D
39.5	48	280	40W,0D	279	39W,6D
40	45	280	40W,0D	279	39W,6D
40.5	32	280	40W,0D	279	39W,6D
41	60	279	39W,6D	279	39W,6D
41.5	51	278	39W,5D	279	39W,6D
42	44	279	39W,6D	279	39W,6D
42.5	30	279	39W,6D	278	39W,5D
43	39	278	39W,5D	279	39W,6D
43.5	25	278	39W,5D	279	39W,6D
44	17	277	39W,4D	278	39W,5D
44.5	23	282	40W,2D	279	39W,6D
45	15	280	40W,0D	279	39W,6D
45.5	19	276	39W,3D	279	39W,6D
46	4	284	40W,4D	280	40W,0D