Table 2.
Incidence of OASIS in different subgroups of women. Data are presented in frequencies (and numbers). p Values from χ2 test
| Primiparous women |
Multiparous women |
|||||
|---|---|---|---|---|---|---|
| Time period | 2003–2005 | 2008–2010 | 2003–2005 | 2008–2010 | ||
| OASIS | 6.1 (489/8051) | 3 (263/8837) | 1.5 (102/6736) | 0.7 (53/8085) | ||
| Risk factors | ||||||
| Age (years) | P | P | ||||
| 15–29 | 5.5 (212/3885) | 2.8 (107/3872) | <0.001 | 1.4 (25/1849) | 0.5 (9/1730) | 0.01 |
| 30–34 | 6.7 (212/3164) | 3.3 (118/3604) | <0.001 | 1.6 (45/2823) | 0.7 (22/3287) | 0.001 |
| 35–51 | 6.5 (65/1002) | 2.8 (38/1361) | <0.001 | 1.6 (32/2064) | 0.7 (22/3068) | 0.004 |
| Birthweight (g) | ||||||
| 720–2999 | 3 (39/1321) | 1.6 (23/1446)) | 0.016 | 0.4 (3/794) | 0.5 (5/938) | 0.63 |
| 3000–3499 | 4.4 (135/3050) | 2.6 (90/3470) | <0.001 | 0.8 (18/2191) | 0.4 (10/2591) | 0.049 |
| 3500–3999 | 7.2 (192/2670) | 3.4 (101/2983) | <0.001 | 1.3 (33/2447) | 0.6 (19/3029) | 0.006 |
| 4000–4499 | 11.2 (99/885) | 4.8 (39/821) | <0.001 | 3.2 (34/1049) | 0.7 (9/1247) | <0.001 |
| 4500–5850 | 19.2 (24/125) | 8.5 (10/117) | 0.017 | 5.5 (14/255) | 3.6 (10/280) | 0.28 |
| Delivery method | ||||||
| Spontaneous | 4.8 (318/6558) | 2.5 (170/6918) | <0.001 | 1.4 (91/6479) | 0.6 (45/7793) | <0.001 |
| Ventouse | 10.8 (144/1331) | 5 (90/1802) | <0.001 | 3.4 (8/234) | 2.9 (8/273) | 0.75 |
| Forceps | 16.7 (27/162) | 2.6 (3/117) | <0.001 | 13 (3/23) | 0 (0/19) | 0.10 |
| Episiotomy, all deliveries | ||||||
| Yes | 6.6 (166/2528) | 3 (96/3203) | <0.001 | 2 (10/492) | 1.8 (12/656) | 0.80 |
| No | 5.8 (323/5523) | 3 (167/5634) | <0.001 | 1.5 (92/6244) | 0.6 (41/7429) | <0.001 |
| Episiotomy, spontaneous deliveries | ||||||
| Yes | 4 (65/1620) | 2.2 (34/1569) | <0.003 | 1.3 (5/396) | 1.3 (6/477) | 1 |
| No | 5.1 (253/4938) | 2.5 (136/5349) | <0.001 | 1.4 (86/6083) | 0.5 (39/7316) | <0.001 |
| Episiotomy, instrumental deliveries | ||||||
| Yes | 11.1 (101/908) | 3.8 (62/1634) | <0.001 | 5.2 (5/96) | 3.4 (6/179) | 0.45 |
| No | 12 (70/585) | 10.9 (31/285) | 0.64 | 3.7 (6/161) | 1.8 (2/113) | 0.34 |
| Duration second stage (min) | ||||||
| 0–09 | 4.6 (13/281) | 3.3 (9/273) | 0.42 | 0.9 (20/2335) | 0.4 (10/2390) | 0.058 |
| 10–29 | 4 (99/2455) | 2.9 (74/2591) | 0.02 | 1.5 (50/3361) | 0.5 (21/4505) | <0.001 |
| 30–59 | 5.5 (180/3290) | 2.5 (93/3673) | <0.001 | 2.9 (24/839) | 1.7 (16/957) | 0.09 |
| 60–205 | 9.7 (193/1994) | 3.8 (87/2288) | <0.001 | 4 (7/174) | 2.3 (5/219) | 0.32 |
| Epidural | ||||||
| Yes | 6.5 (228/3494) | 3 (128/4267) | <0.001 | 2 (20/1008) | 0.8 (12/1419) | 0.015 |
| No | 5.7 (261/4557) | 3 (135/4570) | <0.001 | 1.4 (82/5728) | 0.6 (41/6666) | <0.001 |
| Shoulder dystocia | ||||||
| Yes | 15.8 (12/76)) | 14.1 (9/64) | 0.78 | 5.7 (5/87) | 4.1 (3/73) | 0.64 |
| No | 6 (477/7975) | 2.9 (254/8773) | <0.001 | 1.5 (97/6649) | 0.6 (50/8012) | <0.001 |
| Occiput posterior presentation | ||||||
| Yes | 11.4 (20/176) | 6.9 (17/245) | 0.11 | 0.7 (1/150) | 1.7 (4/237) | 0.39 |
| No | 6 (469/7875) | 2.9 (246/8592) | <0.001 | 1.5 (101/6586) | 0.6 (49/7848) | <0.001 |
| Induced labour | ||||||
| Yes | 5.5 (75/1365) | 3 (50/1650) | 0.001 | 1.3 (12/903) | 0.7 (9/1269) | 0.18 |
| No | 6.2 (414/6686) | 3 (213/7187) | <0.001 | 1.5 (90/5833) | 0.6 (44/6816) | <0.001 |
OASIS, obstetric anal sphincter injuries.