Descriptive table of the study population
| All | IBD | CD | UC | |||||
| N | % | n | % | n | % | n | % | |
| Variable | 827 239 | 100.0 | 51 | 100.0 | 20 | 100.0 | 24 | 100.0 |
| Sex | ||||||||
| Males | 425 212 | 51.4 | 26 | 51.0 | 12 | 60.0 | 11 | 45.8 |
| Females | 402 027 | 48.6 | 25 | 49.0 | 8 | 40.0 | 13 | 54.2 |
| Systemic antibiotic exposure during pregnancy | 140 665 | 17.0 | 15 | 29.4 | 7 | 35.0 | 5 | 20.8 |
| Phenoxymethylpenicillin (PcV) | 60 701 | 7.3 | 8 | 15.7 | 4 | 20.0 | 3 | 12.5 |
| Pivmecillinam | 34 264 | 4.1 | 2 | 3.9 | 1 | 5.0 | 1 | 4.2 |
| Nitrofurantoin | 30 904 | 3.7 | 4 | 7.8 | 1 | 5.0 | 2 | 8.3 |
| Other | 42 672 | 5.2 | 5 | 9.8 | 4 | 20.0 | 0 | 0 |
| Number of prescriptions during pregnancy (any)* | ||||||||
| 1 | 100 549 | 12.2 | 10 | 19.6 | 4 | 20.0 | 3 | 12.5 |
| 2 | 26 357 | 3.2 | 3 | 5.9 | 2 | 10.0 | 1 | 4.2 |
| ≥3 | 13 759 | 1.7 | 2 | 3.9 | 1 | 5.0 | 1 | 4.2 |
| Systemic antibiotic exposure in infantile age | 539 809 | 65.3 | 43 | 84.3 | 16 | 80.0 | 20 | 83.3 |
| PcV | 460 283 | 55.6 | 38 | 74.5 | 14 | 70.0 | 17 | 70.8 |
| Amoxicillin | 152 052 | 18.4 | 15 | 29.4 | 7 | 35.0 | 5 | 20.8 |
| Flucloxacillin | 80 814 | 9.8 | 13 | 25.5 | 5 | 25.0 | 4 | 16.7 |
| Other | 204 387 | 24.7 | 28 | 54.9 | 10 | 50.0 | 11 | 45.8 |
| Number of prescriptions in infantile age (any)* | ||||||||
| 1 | 166 007 | 20.1 | 3 | 5.9 | 1 | 5.0 | 2 | 8.3 |
| 2 | 111 761 | 13.5 | 8 | 15.7 | 2 | 10.0 | 6 | 25.0 |
| ≥3 | 262 041 | 31.7 | 32 | 62.7 | 13 | 65.0 | 12 | 50.0 |
| Mothers’ diagnoses | ||||||||
| IBD | 6 780 | 0.8 | 7 | 13.7 | 4 | 20.0 | 2 | 8.3 |
| CD | 1 943 | 0.2 | 2 | 3.9 | 2 | 10.0 | 0 | 0.0 |
| UC | 3 598 | 0.4 | 5 | 9.8 | 2 | 10.0 | 2 | 8.3 |
| Fathers’ diagnoses | ||||||||
| IBD | 7 333 | 0.9 | 4 | 7.8 | 0 | 0.0 | 2 | 8.3 |
| CD | 1 868 | 0.2 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 |
| UC | 3 972 | 0.5 | 1 | 2.0 | 0 | 0.0 | 0 | 0.0 |
| Parents’ highest achieved education | ||||||||
| 0–12 years | 337 312 | 40.8 | 18 | 35.3 | 8 | 40.0 | 7 | 29.2 |
| >12 years | 485 926 | 58.7 | 33 | 64.7 | 12 | 60.0 | 17 | 70.8 |
| Missing | 4 001 | 0.5 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 |
| Mother’s country of birth | ||||||||
| Sweden | 646 032 | 78.1 | 42 | 82.4 | 18 | 90.0 | 20 | 83.3 |
| Other | 181 207 | 21.9 | 9 | 17.7 | 2 | 10.0 | 4 | 16.7 |
| Father’s country of birth | ||||||||
| Sweden | 630 372 | 76.2 | 39 | 76.5 | 18 | 90.0 | 19 | 79.2 |
| Other | 178 669 | 21.6 | 12 | 23.5 | 2 | 10.0 | 5 | 20.8 |
| Missing | 18 198 | 2.2 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 |
| Mode of delivery | ||||||||
| Vaginal | 679 693 | 82.2 | 43 | 84.3 | 16 | 80.0 | 20 | 83.3 |
| Caesarean section | 147 107 | 17.8 | 8 | 15.7 | 4 | 20.0 | 4 | 16.7 |
| Missing | 439 | 0.1 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 |
| Maternal smoking at first visit to the antenatal care clinic | ||||||||
| Yes | 51 892 | 6.3 | 3 | 5.9 | 1 | 5.0 | 1 | 4.2 |
| No | 741 727 | 89.7 | 46 | 90.2 | 17 | 85.0 | 23 | 95.8 |
| Missing | 33 620 | 4.1 | 2 | 3.9 | 2 | 10.0 | 0 | 0.0 |
| Maternal age at delivery (years) | ||||||||
| ≤19 | 12 060 | 1.5 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 |
| 20–24 | 105 879 | 12.8 | 4 | 7.8 | 2 | 10.0 | 1 | 4.2 |
| 25–29 | 237 650 | 28.7 | 18 | 35.3 | 7 | 35.0 | 7 | 29.2 |
| 30–34 | 287 319 | 34.7 | 18 | 35.3 | 5 | 25.0 | 12 | 50.0 |
| ≥35 | 184 330 | 22.3 | 11 | 21.6 | 6 | 30.0 | 4 | 16.7 |
| Missing | 1 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 |
| Parity (at current delivery) | ||||||||
| 1 | 361 332 | 43.7 | 26 | 51.0 | 11 | 55.0 | 10 | 41.7 |
| ≥2 | 465 907 | 56.3 | 25 | 49.0 | 9 | 45.0 | 14 | 58.3 |
Any—any type of systemic antibiotics (Anatomical Therapeutic Chemical: J01).
‘Other’ antibiotics during childhood—tetracyclines (J01A), penicillins with extended spectrum (J01CA) (except amimoxicillin), beta-lactamase-resistant penicillins (J01CF) (except flucloxacillin), combinations of penicillins, incl. beta-lactamase inhibitors (J01CR), cephalosporins (J01DB-DE), monobactams (J01DF), carbapenems (J01DH), trimethoprim (J01EA), combinations of sulfonamides and trimethoprim (J01EE), macrolides (J01FA), lincosamides (J01FF), other aminoglycosides (J01GB), fluoroquinolones (J01MA), other antibacterials (J01X).
‘Other’ antibiotics during pregnancy—tetracyclines (J01A), penicillins with extended spectrum (J01CA) (except pivmecillinam), beta-lactamase-sensitive penicillins (J01CE) (except phenoxymethylpenicillin), beta-lactamase-resistant penicillins (J01CF), combinations of penicillins, incl. beta-lactamase inhibitors (J01CR), cephalosporins (J01DB-DD), monobactams (J01DF), carbapenems (J01DH), trimethoprim (J01EA), combinations of sulfonamides and trimethoprim (J01EE), macrolides (J01FA), lincosamides (J01FF), other aminoglycosides (J01GB), fluoroquinolones (J01MA), other antibacterials (J01X) (except nitrofurantoin).
*Independent on time in relation to diagnosis (ie, either before or after onset of diagnosis).