Table 1.
Characteristics of women with RPL (recurrent pregnancy loss) and women without RPL at each pregnancy identified in the Swedish Medical Birth Register and the Swedish National Patient Register.
| Maternal Characteristics | RPL a n = 4971 (%) | No RPL a n = 57410 * (%) | p-Value b | Primary a n = 2335 (%) | Secondary a n = 2636 (%) | p-Value c |
|---|---|---|---|---|---|---|
| Age b,c | ||||||
| <25 | 303 (6.1) | 11,621 (20.2) | <0.001 | 226 (9.7) | 77 (2.9) | <0.001 |
| 25–29 | 907 (18.2) | 15,541 (27.1) | 532 (22.8) | 375 (14.2) | ||
| 30–34 | 1637 (32.9) | 17,073 (29.7) | 815 (34.9) | 822 (31.2) | ||
| 35–39 | 1499 (30.2) | 10,493 (18.3) | 541 (23.2) | 958 (36.3) | ||
| >40 | 625 (12.6) | 2682 (4.7) | 221 (9.5) | 404 (15.3) | ||
| Parity b | ||||||
| 1 | 2335 (47.0) | 24,510 (42.7) | <0.001 | 2335 (100) | 0 (0.0) | - |
| 2 | 1806 (36.3) | 20,579 (35.8) | - | 1806 (68.5) | ||
| 3 | 572 (11.5) | 8025 (14.0) | - | 572 (21.7) | ||
| 4+ | 258 (5.2) | 4296 (7.5) | - | 258 (9.8) | ||
| BMI b,c | ||||||
| <18.5 | 64 (1.3) | 1407 (2.5) | <0.001 | 37 (1.6) | 27 (1.0) | <0.001 |
| 18.5–24.9 | 2450 (49.3) | 29,964 (52.2) | 1192 (51.0) | 1258 (47.7) | ||
| 25.0–29.9 | 1314 (26.4) | 12,187 (21.2) | 557 (23.9) | 757 (28.7) | ||
| >30.0 | 695 (14.0) | 5494 (9.6) | 312 (13.4) | 383 (14.5) | ||
| Missing (or not recorded) | 448 (9.0) | 8358 (14.6) | 237 (10.1) | 211 (8.0) | ||
| Smoking b First antenatal visit | ||||||
| Yes | 300 (6.0) | 5805 (10.1) | <0.001 | 126 (5.4) | 174 (6.6) | 0.09 |
| No | 4417 (88.9) | 48,412 (84.3) | 2077 (89.0) | 2340 (88.8) | ||
| Missing (or not recorded) | 254 (5.1) | 3193 (5.6) | 132 (5.7) | 122 (4.6) | ||
| Mother’s country of birth b | ||||||
| Nordic | 3990 (80.3) | 47067 (82) | <0.05 | 1897 (81.2) | 2093 (79.4) | 0.10 |
| Non-nordic | 981 (19.7) | 10,343 (18.0) | 438 (18.8) | 543 (20.6) | ||
| Assisted reproduction b | ||||||
| Yes | 351 (7.1) | 1327 (2.3) | <0.001 | 269 (11.5) | 82 (3.1) | <0.001 |
| No (or not recorded) | 4620 (92.9) | 56,083 (97.7) | 2066 (88.5) | 2554 (96.9) | ||
| Chronic hypertension | ||||||
| Yes | 50 (1.0) | 242 (0.4) | <0.001 | 18 (0.8) | 32 (1.2) | 0.12 |
| No (or not recorded) | 4921 (99.0) | 57,168 (99.6) | 2317 (99.2) | 2604 (98.8) | ||
| Pre-gestational diabetes b | ||||||
| Yes | 43 (0.9) | 314 (0.5) | <0.05 | 18 (0.8) | 25 (0.9) | 0.50 |
| No (or not recorded) | 4928 (99.1) | 57,096 (99.5) | 2317 (99.2) | 2611 (99.1) | ||
| Hypothyroidism b,c | ||||||
| Yes | 211 (4.2) | 528 (0.9) | <0.001 | 128 (5.5) | 83 (3.1) | <0.001 |
| No (or not recorded) | 4760 (95.8) | 56,882 (99.1) | 2207 (94.5) | 2553 (96.9) | ||
| SLE | ||||||
| Yes | 9 (0.2) | 55 (0.1) | 0.072 | 3 (0.1) | 6 (0.2) | 0.41 |
| No (or not recorded) | 2962 (99.8) | 57,355 (99.9) | 2332 (99.9) | 2630 (99.8) | ||
| IBD | ||||||
| Yes | 41 (0.8) | 353 (0.6) | 0.073 | 18 (0.8) | 23 (0.9) | 0.69 |
| No (or not recorded) | 4930 (99.2) | 57,057 (99.4) | 2317 (99.2) | 2613 (99.1) | ||
| Asthma b | ||||||
| Yes | 435 (8.8) | 3627 (6.3) | <0.001 | 205 (8.8) | 230 (8.7) | 0.95 |
| No (or not recorded) | 4536 (91.2) | 53,783 (93.7) | 2130 (91.2) | 2406 (91.3) | ||
| APLS b | ||||||
| Yes | 11 (0.2) | 3 (0.0) | <0.001 | 5 (0.2) | 6 (0.2) | 0.92 |
| No (or not recorded) | 4960 (99.8) | 57,407 (100) | 2330 (99.8) | 2630 (99.8) | ||
| Thrombophilia b,c | ||||||
| Yes | 60 (1.2) | 47 (0.1) | <0.001 | 39 (1.7) | 21 (0.8) | <0.05 |
| No (or not recorded) | 4911 (98.8) | 57,363 (99.9) | 2296 (98.3) | 2615 (99.2) | ||
| Heart disease | ||||||
| Yes | 1 (0.0) | 7 (0.0) | 0.636 | 0 (0.0) | 1 (0.0) | 0.35 |
| No (or not recorded) | 2970 (100) | 57,403 (100) | 2335 (100) | 2635 (100) | ||
| Kidney disease | ||||||
| Yes | 34 (0.7) | 288 (0.5) | 0.085 | 18 (0.8) | 16 (0.6) | 0.48 |
| No (or not recorded) | 4937 (99.3) | 57,122 (99.5) | 2317 (99.2) | 2620 (99.4) |
RPL: recurrent pregnancy loss; BMI: body mass index; SLE: systemic lupus erythematosus; IBD: inflammatory bowel disease; APLS: antiphospholipid syndrome. * Number of pregnancies by control women. Characteristics at each pregnancy in the control group. a First childbirth after diagnosis with RPL in the National Patient Register; b p < 0.05 = significant difference between women diagnosed with RPL and controls characteristics; c p < 0.05 = significant difference between primary and secondary RPL characteristics.