Table 1 Study characteristics of included primi- and multiparous cases and controls
Primiparous women | Multiparous women | |||||
|---|---|---|---|---|---|---|
Case (n = 275) mean (SD) or n (%) | Control (n = 275) mean (SD) or n (%) | P | Case (n = 146) mean (SD) or n (%) | Control (n = 146) mean (SD) or n (%) | P | |
Non-modifiable variables | ||||||
Birthweight, gram | 3678 (512) | 3468 (561) | < 0.001 | 3975 (541) | 3608 (673) | < 0.001 |
Birthweight quartiles | 275 (50%) | 275 (50%) | < 0.001 | 146 (50%) | 146 (50%) | 0.002 |
< 3300 g | 65 (11.8%) | 102 (18.5%) | 12 (4.1%) | 32 (11.0%) | ||
3300–3659 g | 63 (11.5%) | 78 (14.8%) | 31 (10.6%) | 38 (13.0%) | ||
3660–4039 g | 82 (14.9%) | 54 (9.8%) | 41 (14.0%) | 36 (12.3%) | ||
≥ 4040 g | 65 (11.8%) | 41 (7.5%) | 62 (21.2%) | 40 (13.7%) | ||
Length, cm □ | 51.1 (2.1) | 50.4 (2.5) | < 0.001 | 51.9 (2.5) | 50.8 (3.1) | < 0.001 |
Head circumference, cm□ | 35.2 (1.5) | 34.9 (1.6) | < 0.001 | 36.1 (1.3) | 35.3 (1.6) | < 0.001 |
Gestational age, weeks □ | 40.3 (1.7) | 39.8 (2.1) | 0.002 | 40.5 (1.4) | 39.8 (2.3) | 0.002 |
Gestational age categories□ | 274 (50.6%) | 268 (49.4%) | 0.004 | 145 (51.1%) | 139 (48.9%) | 0.603 |
Preterm (< 37 weeks) | 6 (1.1%) | 16 (1.1%) | 4 (1.4%) | 7 (2.5%) | ||
At term (37–42 weeks) | 234 (43.2%) | 233 (43%) | 131 (46.3%) | 122 (43.0%) | ||
Post term (> 42 weeks) | 34 (6.3%) | 19 (3.5%) | 10 (3.5%) | 10 (3.5%) | ||
Maternal age, years | 26.7 (4.2) | 25.7 (4.7) | 0.004 | 31.0 (4.6) | 29.6 (4.4) | 0.005 |
Maternal age category | 275 (50%) | 275 (50%) | 0.014 | 146 (50%) | 146 (50%) | 0.087 |
< 25 years | 83 (15.1%) | 115 (20.9%) | 11 (3.8%) | 18 (6.2%) | ||
25–29 years | 122 (22.2%) | 107 (19.5%) | 46 (15.8%) | 57 (19.5%) | ||
> 30 years | 70 (12.7%) | 53 (9.6%) | 89 (30.5%) | 71 (24.3%) | ||
Fetal presentation □ | 275 (50%) | 275 (50%) | 0.116 | 146 (50.2%) | 145 (49.8%) | 0.365 |
Occiput anterior | 257 (46.7%) | 257 (46.7%) | 134 (46.1%) | 138 (47.4%) | ||
Deep transverse | 0 | 1 (0.2%) | 0 | 1 (0.3%) | ||
Occiput posterior | 14 (2.6%) | 7 (1.3%) | 9 (3.1%) | 4 (1.4%) | ||
Breech | 4 (0.7%) | 10 (1.8%) | 3 (1.0%) | 2 (0.7%) | ||
Duration of 1st stage, minutes □ | 368.5 (195.8) | 314.8 (186.3) | < 0.001 | 268.4 (163.1) | 197.3 (154.9) | < 0.001 |
Duration of 2nd stage, minutes | 46.6 (27.5) | 41.4 (25.1) | 0.037 | 29.3 (22.3) | 19.2 (17.3) | < 0.001 |
Modifiable variables | ||||||
Induction of labor | 26 (9.5%) | 14 (5.1%) | 0.049 | 13 (8.9%) | 10 (6.9%) | 0.515 |
Amniotomy | 63 (22.9%) | 18 (6.6%) | < 0.001 | 33 (22.6%) | 11 (7.5%) | < 0.001 |
Augmentation with oxytocin | 165 (60%) | 119 (43.3%) | < 0.001 | 71 (46.7%) | 36 (23.7%) | < 0.001 |
Episotomy□ | 190 (69.1%) | 171 (62.2%) | 0.155 | 66 (45.2%) | 34 (23.3%) | < 0.001 |
Maternal birth position□ | 275 (51.0%) | 264 (49.0%) | 0.596 | 146 (51.2%) | 139 (48.8%) | 0.150 |
Supine/sitting | 221 (41.0%) | 203 (37.7%) | 111 (39.0%) | 97 (34.0%) | ||
Side bearing | 19 (3.5%) | 29 (5.4%) | 12 (4.2%) | 20 (7.0%) | ||
Standing | 2 (0.4%) | 2 (0.4%) | 6 (2.1%) | 4 (1.4%) | ||
Kneeling | 15 (2.8%) | 14 (2.6%) | 5 (1.8%) | 11 (3.9%) | ||
Stool | 18 (3.3%) | 16 (3.0%) | 12 (4.2%) | 7 (2.5%) | ||
Instrumental delivery | ||||||
Vacuum extraction | 52 (18.9%) | 22 (8.0%) | < 0.001 | 17 (11.6%) | 3 (2.1%) | 0.001 |
Forceps | 41 (14.9%) | 18 (6.6%) | 0.002 | 8 (5.5%) | 1 (0.7%) | 0.018 |