Table 1.
Characteristics of study population
| Characteristics | Cases (n = 7039) | Controls (n = 70390) | Unadjusted OR | P value* |
|---|---|---|---|---|
| Gestational age at index date (weeks); mean (SD) ** | ||||
| Socio‐demographics status ( n , %) a | 14.3 ± 2.8 | 14.3 ± 2.8 | 0.9904 | |
| Maternal age (years), mean (SD) ** | 28.9 ± 6.3 | 27.9 ± 5.6 | <0.001 | |
| <18 (ref.) | 104 (1.5) | 1035 (1.5) | 1.00 | |
| 18–34 | 5415 (76.9) | 59 612 (84.7) | 1.10 (0.90–1.34) | |
| >34 | 1520 (21.6) | 9743 (13.8) | 1.69 (1.59–1.80) | <0.001 |
| Urban residence (vs. rural residence) | 5816 (82.6) | 57 841 (82.1) | 1.03 (0.97–1.10) | 0.3431 |
| Recipient of social assistance (vs. RAMQ adherent) | 1765 (25.1) | 17 648 (25.1) | 1.00 (0.95–1.06) | 0.9958 |
| Education (≤12 years vs. >12 years) | 2933 (41.7) | 29 710 (42.2) | 0.98 (0.93–1.03) | 0.3818 |
| Living alone (vs. couple) | 1304 (18.5) | 10 592 (15.1) | 1.27 (1.20–1.36) | <0.001 |
| During year before until index date b ( n , %) a | ||||
| Comorbidities | ||||
| Depression c (yes vs. no) | 1328 (18.9) | 9702 (13.8) | 1.42 (1.34–1.52) | <0.001 |
| Asthma c (yes vs. no) | 987 (14.0) | 8335 (11.8) | 1.20 (1.12–1.29) | <0.001 |
| Diabetes mellitus c (yes vs. no) | 128 (1.8) | 1233 (1.8) | 1.04 (0.87–1.24) | 0.6844 |
| Hypertension c (yes vs. no) | 213 (3.0) | 1779 (2.5) | 1.20 (1.04–1.38) | 0.0118 |
| Thyroid disorders c (yes vs. no) | 278 (4.0) | 2581 (3.7) | 1.08 (0.95–1.22) | 0.2304 |
| Urinary tract infection d (yes vs. no) | 745 (10.6) | 6838 (9.7) | 1.10 (1.01–1.18) | 0.0193 |
| Respiratory tract infection d (yes vs. no) | 2325 (33.0) | 21 091 (30.0) | 1.15 (1.09–1.21) | <0.001 |
| Sexually transmitted diseases d (yes vs. no) | 259 (3.7) | 2563 (3.6) | 1.01 (0.89–1.15) | 0.8699 |
| Endometriosis d (yes vs. no) | 72 (1.0) | 441 (0.6) | 1.53 (1.19–1.96) | <0.001 |
| Bacterial vaginosis d (yes vs. no) | 578 (8.2) | 5424 (7.7) | 1.07 (0.98–1.17) | 0.1303 |
| Epilepsy c (yes vs. no) | 142 (2.0) | 881 (1.3) | 1.60 (1.34–1.91) | <0.001 |
| Uterine malformations d (yes vs. no) | 5 (<0.1) | 29 (<0.1) | 1.70 (0.67–4.27) | 0.2546 |
| In the year before the first day of gestation | ||||
| Health care utilization ( n , %) a | ||||
| Inpatient or emergency visit | 2530 (35.9) | 29 030 (32.6) | 1.15 (1.09–1.20) | <0.001 |
| No. of visits to physicians | ||||
| 0 (ref.) | 1900 (27.0) | 20 976 (29.8) | 1.00 | |
| 1–2 | 1404 (20.0) | 15 556 (22.1) | 0.99 (0.93–1.06) | |
| ≥3 | 3735 (53.0) | 33 858 (48.1) | 1.20 (1.15–1.26) | <0.001 |
| Medications | ||||
| Penicillins use (yes vs. no) | 1369 (19.5) | 12 824 (18.2) | 1.07 (1.02–1.14) | 0.0110 |
| *** TMP‐SMX use (yes vs. no) | 89 (1.3) | 763 (1.1) | 1.16 (0.94–1.44) | 0.1665 |
| Other drugs excluding anti‐infective | ||||
| 0 (ref.) | 2179 (31.0) | 24 084 (34.2) | 1.00 | |
| 1–2 | 1597 (22.7) | 16 134 (22.9) | 1.09 (1.02–1.16) | |
| ≥3 | 3263 (46.3) | 30 172 (42.9) | 1.18 (1.12–1.25) | <0.001 |
| Obstetrics complications | ||||
| History of prior SA **** (yes vs. no) | 140 (2.0) | 746 (1.1) | 1.85 (1.55–2.21) | <0.001 |
| History of prior abortion (yes vs. no) | 431 (6.1) | 3128 (4.4) | 1.38 (1.25–1.1) | <0.001 |
| During pregnancy ( n , %) a | ||||
| *** TMP‐SMX use e , f (yes vs. no) | 25 (0.4) | 77 (0.1) | 3.11 (2.01–4.81) | <0.0001 |
| Penicillins f , g (yes vs. no) | 427 (6.1) | 4777 (6.8) | 0.89 (0.81–0.99) | <0.0001 |
P‐value calculated to compared cases of SA and controls using Pearson χ2 test for categorical variables and a t‐test for continuous variables.
SD, standard deviation;
TMP‐SMX, trimethoprim–sulfamethoxazole;
SA, spontaneous abortion.
Unless otherwise stated.
Index date = date of spontaneous abortion for cases and corresponding date for matched controls.
Based on ICD‐9 or ICD‐10 codes or prescription filled for chronic diseases (hypertension, diabetes, asthma, depression, etc.).
Based on ICD‐9 or ICD‐10 codes for urinary tract infections, respiratory tract infections, bacterial vaginosis, endometriosis, sexually transmitted disease and uterine malformations.
Include pregnancies having filled at least one prescription for trimethoprim–sulfamethoxazole only between the start of pregnancy and the index date.
No exposure to antibiotics.
Include pregnancies having filled at least one prescription for penicillins only between the start of pregnancy and the index date.