| Determinant | No. of term and post-term live births | No. undergoing frenotomy | Rate per 1000 live births | Rate ratio (95% CI) | |
|---|---|---|---|---|---|
| Crude | Adjusted* | ||||
| Age, yr | |||||
| < 20 | 11 504 | 61 | 5.3 (4.1-6.8) | 1.23 (0.92-1.65) | 1.12 (0.84-1.49) |
| 20-24 (ref) | 52 289 | 225 | 4.3 (3.8-4.9) | 1.00 (-) | 1.00 (-) |
| 25-29 | 108 508 | 447 | 4.1 (3.7-4.5) | 0.96 (0.82-1.12) | 0.98 (0.83-1.15) |
| 30-34 | 129 939 | 546 | 4.2 (3.9-4.6) | 0.98 (0.84-1.14) | 1.04 (0.89-1.21) |
| 35-39 | 71 894 | 281 | 3.9 (3.5-4.4) | 0.91 (0.76-1.08) | 1.01 (0.84-1.21) |
| ≥ 40 | 15 968 | 50 | 3.1 (2.3-4.1) | 0.73 (0.54-0.99) | 0.82 (0.60-1.12) |
| Parity | |||||
| 0 | 180 970 | 912 | 5.0 (4.7-5.4) | 1.51 (1.37-1.67) | 1.56 (1.40-1.72) |
| ≥ 1 (ref) | 209 121 | 698 | 3.3 (3.1-3.6) | 1.00 (-) | 1.00 (-) |
| Body mass index | |||||
| < 18 | 16 473 | 65 | 3.9 (3.0-5.0) | 0.96 (0.74-1.24) | 0.98 (0.76-1.27) |
| 18-24 (ref) | 167 813 | 691 | 4.1 (3.8-4.4) | 1.00 (-) | 1.00 (-) |
| 25-29 | 56 208 | 231 | 4.1 (3.6-4.7) | 1.00 (0.86-1.16) | 0.99 (0.86-1.56) |
| ≥ 30 | 33 730 | 166 | 4.9 (4.2-5.7) | 1.20 (1.01-1.42) | 1.18 (0.99-1.40) |
| Missing data | 115 881 | 457 | 3.9 (3.6-4.3) | 0.96 (0.85-1.08) | 1.03 (0.91-1.16) |
| Plurality | |||||
| Singleton (ref) | 385 104 | 1 596 | 4.1 (3.9-4.3) | 1.00 (-) | 1.00 (-) |
| Multiple | 4 995 | 14 | 2.8 (1.5-4.7) | 0.68 (0.40-1.14) | 0.79 (0.46-1.36) |
| Infant sex | |||||
| Female (ref) | 190 993 | 534 | 2.8 (2.6-3.0) | 1.00 (-) | 1.00 (-) |
| Male | 199 106 | 1 076 | 5.4 (5.1-5.7) | 1.93 (1.74-2.14) | 1.87 (1.69-2.08) |
| Birth weight,† g | |||||
| 2000-2499 | 5 315 | 17 | 3.2 (1.9-5.1) | 0.84 (0.52-1.36) | 0.87 (0.53-1.41) |
| 2500-2999 | 50 987 | 163 | 3.2 (2.7-3.7) | 0.84 (0.71-1.00) | 0.86 (0.72-1.02) |
| 3000-3499 (ref) | 149 808 | 569 | 3.8 (3.5-4.1) | 1.00 (-) | 1.00 (-) |
| 3500-3999 | 131 133 | 566 | 4.3 (4.0-4.7) | 1.14 (1.01-1.28) | 1.11 (0.99-1.25) |
| 4000-4499 | 44 505 | 245 | 5.5 (4.8-6.2) | 1.45 (1.25-1.68) | 1.39 (1.19-1.62) |
| ≥ 4500 | 8 127 | 49 | 6.0 (4.5-8.0) | 1.59 (1.19-2.12) | 1.49 (1.11-2.00) |
| Year | |||||
| 2004 (ref) | 36 593 | 116 | 3.2 (2.6-3.8) | 1.00 (-) | 1.00 (-) |
| 2005 | 36 791 | 126 | 3.4 (2.9-4.1) | 1.08 (0.84-1.39) | 1.08 (0.84-1.39) |
| 2006 | 37 802 | 112 | 3.0 (2.4-3.6) | 0.93 (0.72-1.21) | 0.93 (0.72-1.21) |
| 2007 | 39 743 | 131 | 3.3 (2.8-3.9) | 1.04 (0.81-1.33) | 1.03 (0.80-1.33) |
| 2008 | 40 267 | 164 | 4.1 (3.5-4.7) | 1.28 (1.01-1.63) | 1.28 (1.01-1.62) |
| 2009 | 40 367 | 154 | 3.8 (3.2-4.5) | 1.20 (0.95-1.53) | 1.20 (0.94-1.53) |
| 2010 | 39 610 | 165 | 4.2 (3.6-4.9) | 1.31 (1.04-1.67) | 1.31 (1.03-1.66) |
| 2011 | 39 827 | 208 | 5.2 (4.5-6.0) | 1.65 (1.31-2.07) | 1.66 (1.32-2.08) |
| 2012 | 39 936 | 204 | 5.1 (4.4-5.9) | 1.61 (1.28-2.02) | 1.62 (1.29-2.04) |
| 2013 | 39 169 | 230 | 5.9 (5.1-6.7) | 1.85 (1.48-2.31) | 1.87 (1.49-2.33) |
Note: CI = confidence interval, ref = reference category.
*Adjusted for all other factors in the table.
†Results for live births < 2000 g not shown because of small number of cases (< 5).