Characteristic | Unmatched cohort | Propensity score–matched cohort | ||||
---|---|---|---|---|---|---|
No. (%)* of women with infertility treatment n = 11 965 | No. (%)* of women with no infertility treatment n = 448 198 | Standardized difference | No. (%)* of women with infertility treatment n = 11 546 | No. (%)* of women with no infertility treatment n = 47 553 | Standardized difference | |
Year | ||||||
2006 | 1225 (10.2) | 62 249 (13.9) | 0.11 | 1197 (10.4) | 5055 (10.6) | 0.01 |
2007 | 1387 (11.6) | 70 515 (15.7) | 0.12 | 1351 (11.7) | 5712 (12.0) | 0.01 |
2008 | 1647 (13.8) | 73 990 (16.5) | 0.08 | 1609 (13.9) | 6882 (14.5) | 0.02 |
2009 | 2150 (18.0) | 78 806 (17.6) | 0.01 | 2066 (17.9) | 8148 (17.1) | 0.02 |
2010 | 2708 (22.6) | 80 154 (17.9) | 0.12 | 2588 (22.4) | 10 637 (22.4) | 0.0 |
2011 | 2848 (23.8) | 82 484 (18.4) | 0.13 | 2735 (23.7) | 11 119 (23.4) | 0.01 |
Maternal age at index pregnancy, yr | ||||||
Mean ± SD | 34.2 ± 4.9 | 30.1 ± 5.5 | 0.79 | 34.0 ± 4.8 | 33.6 ± 5.0 | 0.09 |
18–24 | 213 (1.8) | 74 300 (16.6) | 0.53 | 213 (1.8) | 1791 (3.8) | 0.12 |
25–34 | 6226 (52.0) | 277 239 (61.9) | 0.20 | 6115 (53.0) | 24 787 (52.1) | 0.02 |
35–39 | 3913 (32.7) | 79 466 (17.7) | 0.35 | 3758 (32.5) | 15 214 (32.0) | 0.01 |
40–44 | 1327 (11.1) | 16 489 (3.7) | 0.29 | 1224 (10.6) | 5422 (11.4) | 0.03 |
≥ 45 | 286 (2.4) | 704 (0.2) | 0.20 | 236 (2.0) | 339 (0.7) | 0.11 |
Neighbourhood income quintile† | ||||||
1 (lowest) | 1370 (11.5) | 100 445 (22.4) | 0.30 | 1343 (11.6) | 5797 (12.2) | 0.02 |
2 | 1952 (16.3) | 90 596 (20.2) | 0.10 | 1903 (16.5) | 7970 (16.8) | 0.01 |
3 | 2598 (21.7) | 92 896 (20.7) | 0.02 | 2509 (21.7) | 10 480 (22.0) | 0.01 |
4 | 3231 (27.0) | 92 285 (20.6) | 0.15 | 3104 (26.9) | 12 653 (26.6) | 0.01 |
5 (highest) | 2789 (23.3) | 69 907 (15.6) | 0.20 | 2663 (23.1) | 10 541 (22.2) | 0.02 |
Maternal world region of origin†‡ | ||||||
Africa | 134 (1.1) | 8 281 (1.8) | 0.06 | 129 (1.1) | 534 (1.1) | 0.0 |
Canada | 8967 (74.9) | 323 062 (72.1) | 0.06 | 8650 (74.9) | 35 591 (74.8) | 0.0 |
Caribbean | 102 (0.9) | 7504 (1.7) | 0.07 | 98 (0.8) | 414 (0.9) | 0.0 |
East Asia | 444 (3.7) | 27 705 (6.2) | 0.11 | 437 (3.8) | 1882 (4.0) | 0.01 |
Hispanic America | 233 (1.9) | 9945 (2.2) | 0.02 | 223 (1.9) | 943 (2.0) | 0.0 |
Middle East | 352 (2.9) | 12 168 (2.7) | 0.01 | 337 (2.9) | 1363 (2.9) | 0.0 |
South Asia | 1080 (9.0) | 40 382 (9.0) | 0 | 1039 (9.0) | 4324 (9.1) | 0.0 |
Western nations and Europe | 653 (5.5) | 19 122 (4.3) | 0.06 | 633 (5.5) | 2502 (5.3) | 0.01 |
Comorbidities | ||||||
BMI, median (IQR), kg/m2§ | 25 (22–30) | 25 (22–29) | 0.08 | 25 (22–30) | 25 (22–30) | 0.09 |
Obesity at any visit (BMI > 30 kg/m2) | 731 (6.1) | 22 383 (5.0) | 0.05 | 716 (6.2) | 2842 (6.0) | 0.01 |
Cardiac disease¶ | 411 (3.4) | 12 177 (2.7) | 0.04 | 394 (3.4) | 1511 (3.2) | 0.01 |
Stroke | 12 (0.1) | 403 (0.1) | 0 | 12 (0.1) | 40 (0.1) | 0.01 |
Hypertension | 701 (5.9) | 16 267 (3.6) | 0.11 | 657 (5.7) | 2515 (5.3) | 0.02 |
Diabetes mellitus | 1478 (12.4) | 33 524 (7.5) | 0.16 | 1412 (12.2) | 5342 (11.2) | 0.03 |
Renal disease | 17 (0.1) | 448 (0.1) | 0.01 | 16 (0.1) | 54 (0.1) | 0.01 |
HIV | 9 (0.1) | 411 (0.1) | 0.01 | 9 (0.1) | 32 (0.1) | 0.0 |
Tobacco use** | 408 (3.4) | 54 507 (12.2) | 0.33 | 406 (3.5) | 1820 (3.8) | 0.02 |
Major psychiatric condition | 1967 (16.4) | 73 967 (16.5) | 0 | 1887 (16.3) | 7376 (15.5) | 0.02 |
Endometriosis | 139 (1.2) | 1435 (0.3) | 0.1 | 133 (1.2) | 301 (0.6) | 0.06 |
Polycystic ovarian syndrome | 6 (0.1) | 15 (0.0) | 0.03 | ≤ 5 (0.0) | 6 (0.0) | 0.0 |
Pregnancy characteristics | ||||||
Parity† | ||||||
0 | 8543 (71.4) | 209 443 (46.7) | 0.52 | 8164 (70.7) | 32 630 (68.6) | 0.05 |
1 | 2786 (23.3) | 154 585 (34.5) | 0.25 | 2748 (23.8) | 12 061 (25.4) | 0.04 |
≥ 2 | 635 (5.3) | 84 095 (18.8) | 0.42 | 633 (5.5) | 2861 (6.0) | 0.02 |
No. of previous live births, median (IQR) | 0 (0–1) | 1 (0–1) | 0.57 | 0 (0–1) | 0 (0–1) | 0.05 |
No. of previous miscarriages† | ||||||
0 | 8431 (70.5) | 348 836 (77.8) | 0.17 | 8162 (70.7) | 34 234 (72.0) | 0.03 |
1–2 | 3022 (25.3) | 90 648 (20.2) | 0.12 | 2903 (25.1) | 11 596 (24.4) | 0.02 |
≥ 3 | 511 (4.3) | 8618 (1.9) | 0.14 | 480 (4.2) | 1722 (3.6) | 0.03 |
Multiple gestation in the index pregnancy | 3025 (25.3) | 14 462 (3.2) | 0.66 | 2663 (23.1) | 7115 (15.0) | 0.21 |
Type of infertility treatment in the index pregnancy | ||||||
Intrauterine insemination | 2892 (24.2) | 0 (0.0) | 0.8 | 2778 (24.1) | 0 (0.0) | – |
Ovulation induction | 2820 (23.6) | 0 (0.0) | 0.79 | 2794 (24.2) | 0 (0.0) | – |
In vitro fertilization | 5630 (47.1) | 0 (0.0) | 1.33 | 5366 (46.5) | 0 (0.0) | – |
Intracytoplasmic sperm injection | 623 (5.2) | 0 (0.0) | 0.33 | 608 (5.3) | 0 (0.0) | – |
No. of antenatal visits in the index pregnancy, median (IQR) | 22 (17–29) | 16 (13–20) | 0.87 | 22 (17–28) | 19 (16–25) | 0.25 |
Note: BMI = body mass index, IQR = interquartile range, SD = standard deviation.
↵* Unless specified otherwise.
↵† Data missing in < 1%.
↵‡ Appendix 2 (available at www.cmaj.ca/lookup/suppl/doi:10.1503/cmaj.181124/-/DC1) contains the definitions of each of the maternal world regions of origin.
↵§ Data were available for BMI for 383 543 pregnancies in the unmatched cohort and 47 939 pregnancies in the matched cohort.
↵¶ Congestive heart failure, congenital heart disease, coronary artery disease, cardiac dysthymia, chronic rheumatic heart disease or previous myocardial infarction.
↵** Defined as any use (yes/no) as of 20 weeks’ gestation.