Table 1.

Maternal, fetal and labor characteristics

	Study population Primiparous at term, induced or spont. start of labor (n = 459)	Medical Birth Registry, Norway, 2014 a All deliveries n = 59,065 b All planned vaginal deliveries (n = 54,946) c Primiparous spont. start (n = 14,239) d Primiparous spont. start, vag delivery (n = 12,954)
Maternal characteristics
Maternal age mean, yrs	32	29 a
Cohabiting or married     Missing	439 (96%) 9 (2%)	55,041 (93%) a
BMI median    Missing	22.0 43 (9.4%)	24.2 a
Fetal characteristics
Gestational age, days	283 (SD = 9)	275 (SD = 14) a
Mean birth weight, g	3438	3489 a
5 min Apgar score < 7  Missing	3 (0.7%) 5 (1.1%)	1059 (1.8%) a
Onset of labor
Spontaneous	346 (75%)	42,848 (78%) b
Induced	113 (25%)	12,098 (22%) b
Mode of delivery
Normal vaginal	296 (64%)	10,093 (71%) c
Operative vaginal	114 (25%)	2861 (20%) c
Cesarean section	49 (11%)	1285 (9%) c
Labor characteristics
Anal sphincter tears	7 (1.5%)	406 (3.1%) d
Missing	5 (1.1%)
Episiotomy	155 (34%)	4469 (34%) d
Bleeding ≥500 ml	109 (24%)	15,802 (27%) a