Comparison of baseline characteristics between exposed (use of analgesics) and unexposed (no analgesic use) groups of pregnancies (p values <0.05 shown in bold)
| Baseline characteristics | No analgesic (n=1 07 143) n (%) | At least one analgesic (n=43 998) n (%) | P value* | Paracetamol only (n=24 099) n (%) | P value* | Ibuprofen/Aspirin/Naproxen (n=762) n (%) | P value* | No analgesic 2005–2015 (n=20 544) n (%) | Diclofenac only 2005–2015 (n=10 291) n (%) | P value† |
| Year of delivery | ||||||||||
| 1985–1994 | 50 152 (46.8) | 5737 (13.0) | <0.001 | 5390 (22.4) | <0.001 | 213 (28.0) | <0.001 | n/a | n/a | <0.001 |
| 1995–2004 | 36 447 (34.0) | 7263 (16.5) | 6571 (27.3) | 321 (42.1) | n/a | n/a | ||||
|
2005–2015/ 2005–2009‡ | 20 544 (19.2) n/a | 30 998 (70.5) n/a | 12 138 (50.4) n/a | 228 (29.9) n/a | n/a 11 105 (54.1) | n/a 4021 (39.1) | ||||
| 2010–2015‡ | n/a | n/a | n/a | n/a | 9439 (45.9) | 6270 (60.9) | ||||
| Maternal age (years) at delivery | ||||||||||
| <20 | 9236 (8.6) | 3834 (8.7) | <0.001 | 2936 (12.2) | <0.001 | 34 (4.5) | <0.001 | 1286 (6.3) | 311 (3.0) | <0.001 |
| 20–25 | 24 249 (22.6) | 8700 (19.8) | 5932 (24.6) | 113 (14.8) | 3436 (16.7) | 1152 (11.2) | ||||
| 26–35 | 63 499 (59.3) | 25 367 (57.7) | 12 896 (53.5) | 464 (60.9) | 12 664 (61.1) | 6628 (64.4) | ||||
| >35 | 10 159 (9.5) | 6097 (13.9) | 2335 (9.7) | 151 (19.8) | 3158 (15.4) | 2200 (21.4) | ||||
| Previous parity | ||||||||||
| Nulliparity (0) | 48 684 (45.4) | 23 353 (53.1) | <0.001 | 12 510 (51.9) | <0.001 | 300 (39.4) | 0.004 | 8336 (40.6) | 5004 (48.6) | <0.001 |
| Multiparity (1–11) | 58 457 (54.6) | 20 639 (46.9) | 11 587 (48.1) | 462 (60.6) | 12 206 (59.4) | 5284 (51.4) | ||||
| Missing | 2 (<0.1)§ | 6 (<0.1)§ | 2 (<0.1)§ | 0 (0.0)§ | 2 (<0.1)§§ | 3 (<0.1)§§ | ||||
| Maternal BMI | ||||||||||
| Underweight (<18.5) | 1998 (2.4) | 869 (2.2) | <0.001 | 545 (2.6) | <0.001 | 10 (1.5) | 0.007 | 492 (2.7) | 174 (1.9) | <0.001 |
|
Normal weight (18.5–24.9) | 50 127 (60.8) | 18 958 (48.8) | 10 486 (50.5) | 361 (55.0) | 10 239 (55.2) | 4671 (50.0) | ||||
| Overweight (25.0–29.9) | 20 500 (24.9) | 10 960 (28.2) | 5733 (27.6) | 192 (29.5) | 4930 (26.6) | 2630 (28.1) | ||||
| Obese (≥30.0) | 9773 (11.9) | 8046 (20.7) | 3995 (19.2) | 88 (13.5) | 2881 (15.5) | 1871 (20.0) | ||||
| Missing data | 24 745 (23.1)§ | 5165 (11.7)§ | 3340 (13.9)§ | 111 (14.6)§ | 2002 (9.7)§ | 945 (9.2)§ | ||||
| Gestation weeks at earliest antenatal visit | ||||||||||
| First trimester | 69 896 (65.4) | 36 789 (83.7) | <0.001 | 19 075 (79.2) | <0.001 | 569 (75.0) | <0.001 | 18 155 (88.4) | 9185 (89.4) | 0.036 |
| Second trimester | 29 269 (27.4) | 5791 (13.2) | 4117 (17.1) | 166 (21.9) | 1770 (8.6) | 829 (8.1) | ||||
| Third trimester | 7741 (7.2) | 1376 (3.1) | 890 (3.7) | 24 (3.2) | 605 (2.9) | 264 (2.6) | ||||
| Missing | 237 (0.2)§ | 42 (0.1)§ | 17 (0.1)§§ | 3 (0.4)§ | 14 (0.1)§ | 13 (0.1)§ | ||||
| Maternal smoking status | ||||||||||
| Unknown | 6505 (6.1)§ | 819 (1.9)§ | <0.001 | 500 (2.1)§ | <0.001 | 32 (4.2)§ | 0.132 | 448 (2.2)§ | 155 (1.5)§ | <0.001 |
| Ex-smoker | 5952 (5.6) | 3363 (7.6) | 1923 (8.1) | 35 (4.8) | 1427 (7.1) | 660 (6.5) | ||||
| Non-smoker | 70 319 (69.9) | 31 421 (72.8) | 15 755 (66.8) | 534 (73.2) | 15 525 (77.3) | 8368 (82.6) | ||||
| Smoker | 24 367 (24.2) | 8395 (19.4) | 5921 (25.1) | 161 (22.2) | 3144 (15.6) | 1108 (10.9) | ||||
| Maternal SIMD decile | ||||||||||
| Least deprived (7–10) | 65 227 (61.8) | 25 192 (57.9) | <0.001 | 12 807 (53.8) | <0.001 | 501 (66.3) | 0.012 | 12 806 (62.9) | 6714 (66.1) | <0.001 |
| Most deprived (1–6) | 40 321 (38.2) | 18 289 (42.1) | 11 017 (46.2) | 255 (33.7) | 7564 (37.1) | 3442 (33.9) | ||||
| Missing | 1595 (1.5)§ | 517 (1.2)§ | 275 (1.1)§ | 6 (0.8)§ | 174 (0.8)§ | 135 (1.3)§ | ||||
| Maternal hypertensive disorders | ||||||||||
| None | 91 276 (85.2) | 35 529 (80.8) | <0.001 | 18 635 (77.3) | <0.001 | 636 (83.5) | 0.001 | 18 851 (91.8) | 9273 (90.1) | <0.001 |
| Gestational hypertension | 13 029 (12.2) | 5501 (12.5) | 3584 (14.9) | 88 (11.5) | 1165 (5.7) | 690 (6.7) | ||||
| Pre-eclampsia | 2780 (2.6) | 2941 (6.7) | 1861 (7.7) | 38 (5.0) | 523 (2.5) | 324 (3.1) | ||||
| Eclampsia | 58 (0.1) | 27 (0.1) | 19 (0.1) | 0 (0.0) | 5 (<0.1) | 4 (<0.1) | ||||
| Maternal antepartum haemorrhage | ||||||||||
| No haemorrhage | 97 527 (91.0) | 37 673 (85.6) | <0.001 | 20 306 (84.3) | <0.001 | 684 (89.8) | 0.434 | 18 549 (90.3) | 9244 (89.8) | <0.001 |
| Abruption | 697 (0.7) | 468 (1.1) | 221 (0.9) | 8 (1.0) | 103 (0.5) | 106 (1.0) | ||||
| Placenta previa | 308 (0.3) | 368 (0.8) | 152 (0.6) | 2 (0.3) | 23 (0.1) | 114 (1.1) | ||||
| Unspecified | 8611 (8.0) | 5489 (12.5) | 3420 (14.2) | 68 (8.9) | 1869 (9.1) | 827 (8.0) | ||||
| Type of labour | ||||||||||
| Elective caesarean section | 5967 (5.6) | 6925 (15.7) | <0.001 | 1384 (5.7) | <0.001 | 67 (8.8) | <0.001 | 616 (3.0) | 3843 (37.3) | <0.001 |
| Induced | 24 120 (22.5) | 16 276 (37.0) | 10 067 (41.8) | 228 (29.9) | 3895 (19.0) | 1998 (19.4) | ||||
| Spontaneous | 77 056 (71.9) | 20 797 (47.3) | 12 648 (52.5) | 467 (61.3) | 16 033(78.0) | 4450 (43.2) | ||||
| Type of delivery | ||||||||||
| Spontaneous vaginal delivery | 75 027 (70.1) | 19 287 (43.8) | <0.001 | 15 983 (66.3) | <0.001 | 496 (65.2) | 0.003 | 16 398 (79.8) | 1403 (13.6) | <0.001 |
| Instrumental | 15 409 (14.4) | 8107 (18.4) | 4043 (16.8) | 120 (15.8) | 2546 (12.4) | 1927 (18.7) | ||||
| Caesarean section | 15 566 (14.5) | 16 351 (37.2) | 3879 (16.1) | 141 (18.5) | 1509 (7.3) | 6937 (67.4) | ||||
| Other | 1096 (1.0) | 247 (0.6) | 191 (0.8) | 4 (0.5) | 89 (0.4) | 24 (0.2) | ||||
| Missing | 45 (<0.1)§ | 6 (<0.1)§ | 3 (<0.1)§§ | 1 (0.1)§ | 2 (<0.1)§ | 0 (0.0)§ | ||||
| Analgesia during labour | ||||||||||
| No | 105 176 (98.2) | 36 117 (82.1) | <0.001 | 20 974 (87.0) | <0.001 | 729 (95.7) | <0.001 | 19 915 (96.9) | 8235 (80.0) | <0.001 |
| Yes | 1967 (1.8) | 7881 (17.9) | 3125 (13.0) | 33 (4.3) | 629 (3.1) | 2056 (20.0) | ||||
| Baby presentation at delivery | ||||||||||
| Occiput posterior | 11 571 (10.8) | 8152 (18.6) | <0.001 | 2636 (11.0) | 0.525 | 68 (8.9) | 0.093 | 1401 (6.8) | 2967 (28.9) | <0.001 |
| Occiput anterior | 95 352 (89.2) | 35 745 (81.4) | 21 409 (89.0) | 694 (91.1) | 19 100 (93.2) | 7306 (71.1) | ||||
| Missing | 220 (0.2)§ | 101 (0.2)§ | 54 (0.2)§ | 0 (0.0)§ | 43 (0.2)§ | 18 (0.2)§ | ||||
| Sex of baby | ||||||||||
| Female | 52 265 (48.8) | 21 139 (48.0) | 0.010 | 11 739 (48.7) | 0.861 | 367 (48.2) | 0.732 | 10 124 (49.3) | 4907 (47.7) | 0.008 |
| Male | 54 866 (51.2) | 22 852 (51.9) | 12 354 (51.3) | 395 (51.8) | 10 417 (50.7) | 5384 (52.3) | ||||
| Missing | 12 (<0.1)§ | 7 (<0.1)§ | 6 (<0.1)§ | 0 (0.0)§ | 3 (<0.1)§ | 0 (0.0)§ | ||||
*P value in comparison with the first (‘no analgesic’) column.
†P value in comparison with ‘no analgesic 2005–2015’ control column.
‡Only applicable to diclofenac 2005–2015 analysis.
§Percentage of missing data on total, not included in the analysis.
BMI, body mass index; n, number of pregnancies; n/a, not applicable; SIMD, Scottish Index of Multiple Deprivation.