Table 2.
Maternal characteristics at the start of pregnancy, by ASM exposure status
| Variable | Total | Unexposed to ASMs in first trimester, n (%) | First-trimester ASM exposure, n (%) | |
| 1 023 787 (100.0) | 1 015 955 (100.0) | 7832 (100.0) | ||
| Age in years | <18 | 38 216 (3.7) | 38 055 (3.7) | 161 (2.1) |
| 18–24 | 231 835 (22.6) | 230 299 (22.7) | 1536 (19.6) | |
| 25–29 | 265 563 (25.9) | 263 527 (25.9) | 2036 (26.0) | |
| 30–34 | 285 357 (27.9) | 283 181 (27.9) | 2176 (27.8) | |
| ≥35 | 202 816 (19.8) | 200 893 (19.8) | 1923 (24.6) | |
| ASM indication* (women could have multiple indications, thus contribute to several groups) | Epilepsy | 13 234 (1.3) | 8509 (64.3) | 4725 (35.70) |
| Bipolar and other psychiatric | 370 043 (36.1) | 365 041 (98.7) | 5002 (1.3) | |
| Other somatic | 134 475 (13.1) | 132 162 (98.3) | 2313 (1.7) | |
| No recorded indication | 587 261 (57.4) | 587 053 (99.9) | 208 (0.1) | |
| IMD quintile | 1 (least deprived) | 194 057 (19.0) | 192 854 (19.0) | 1203 (15.4) |
| 2 | 178 762 (17.5) | 177 569 (17.5) | 1193 (15.2) | |
| 3 | 196 900 (19.2) | 195 515 (19.2) | 1385 (17.7) | |
| 4 | 208 567 (20.4) | 206 804 (20.4) | 1763 (22.5) | |
| 5 (most deprived) | 245 501 (24.0) | 243 213 (23.9) | 2288 (29.2) | |
| Ethnicity | White | 645 744 (63.1) | 640 775 (63.1) | 4969 (63.4) |
| South Asian | 32 858 (3.2) | 32 708 (3.2) | 150 (1.9) | |
| Black | 17 869 (1.7) | 17 792 (1.8) | 77 (1.0) | |
| Other | 11 580 (1.1) | 11 514 (1.1) | 66 (0.8) | |
| Mixed | 6950 (0.7) | 6911 (0.7) | 39 (0.5) | |
| Not stated | 308 786 (30.2) | 306 255 (30.1) | 2531 (32.3) | |
| Year of pregnancy start | 1995–2000 | 136 079 (13.3) | 135 396 (13.3) | 683 (8.7) |
| 2001–2005 | 245 206 (24.0) | 243 880 (24.0) | 1326 (16.9) | |
| 2006–2010 | 305 563 (29.8) | 303 521 (29.9) | 2042 (26.1) | |
| 2011–2015 | 249 123 (24.3) | 246 697 (24.3) | 2426 (31.0) | |
| 2016–2018 | 87 816 (8.6) | 86 461 (8.5) | 1355 (17.3) | |
| Smoking status | Non-smoker | 415 837 (40.6) | 413 174 (40.7) | 2663 (34.0) |
| Current smoker | 307 607 (30.0) | 304 712 (30.0) | 2895 (37.0) | |
| Ex-smoker | 245 838 (24.0) | 243 786 (24.0) | 2052 (26.2) | |
| Not stated | 54 505 (5.3) | 54 283 (5.3) | 222 (2.8) | |
| BMI | Underweight | 32 972 (3.2) | 32 729 (3.2) | 243 (3.1) |
| Normal weight | 463 975 (45.3) | 461 062 (45.4) | 2913 (37.2) | |
| Overweight | 239 081 (23.4) | 237 260 (23.4) | 1821 (23.3) | |
| Obese | 182 915 (17.9) | 180 703 (17.8) | 2212 (28.2) | |
| Not stated | 104 844 (10.2) | 104 201 (10.3) | 643 (8.2) | |
| Problem drinking | 10 176 (1.0) | 10 017 (1.0) | 159 (2.0) | |
| Illicit drug use | 2294 (0.2) | 2182 (0.2) | 112 (1.4) | |
| Primary care consultations† | 0 | 83 181 (8.1) | 82 986 (8.2) | 195 (2.5) |
| 1–3 | 271 949 (26.6) | 271 424 (26.7) | 525 (6.7) | |
| 4–10 | 439 136 (42.9) | 436 788 (43.0) | 2348 (30.0) | |
| >10 | 229 521 (22.4) | 224 757 (22.1) | 4764 (60.8) | |
| Other prescriptions† | Antipsychotics | 808 (0.1) | 754 (0.1) | 54 (0.7) |
| Antidepressants | 114 288 (11.2) | 111 534 (11.0) | 2754 (35.2) | |
| Multivitamins | 603 (0.1) | 591 (0.1) | 12 (0.2) | |
| Folic acid | 268 760 (26.3) | 263 859 (26.0) | 4901 (62.6) | |
| Previous miscarriage | 100 302 (9.8) | 99 482 (9.8) | 820 (10.5) |
*Bipolar disorder and other psychiatric conditions (generalised anxiety disorder, depression and schizophrenia), other somatic conditions (neuropathic pain, restless leg syndrome and migraine).
†In year before pregnancy.
ASM, antiseizure medication; BMI, body mass index; IMD, Index of Multiple Deprivation.