RT Journal
A1 Kuehn BM
T1 LOnger labor
JF JAMA
JO JAMA
YR 2012
FD May 23
VO 307
IS 20
SP 2139
OP 2139
DO 10.1001/jama.2012.4796
UL http://dx.doi.org/10.1001/jama.2012.4796
AB 
The researchers compared data from about 40 000 deliveries between 1959 and 1966 with data from 100 000 deliveries between 2002 and 2006 (Laughon SK et al. Am J Obstet Gynecol. doi: 10.1016/j.ajog.2012.03.003 [published online March 12, 2012]). Labor lasted on average 2 hours longer for women from the later cohort who had already delivered 1 child compared with the women in the earlier group. Infants born more recently were born 5 days earlier on average and were likely to weigh more.