Table 1.
Population characteristics by ART exposure status
| Characteristics | ART group | Non-ART group | Entire cohort |
|---|---|---|---|
| (n = 30 625) | (n = 9988) | (n = 40 613) | |
| No. (%) | No. (%) | No. | |
| Year of birth | |||
| <1955 | 3597 (11.8) | 2245 (22.5) | 5842 |
| 1955-1959 | 8622 (28.2) | 2617 (26.2) | 11 239 |
| 1960-1964 | 10 468 (34.2) | 2759 (27.6) | 13 227 |
| ≥1965 | 7938 (25.9) | 2367 (23.7) | 10 305 |
| Major subfertility diagnosisa | |||
| Male factor | 8205 (26.8) | 1646 (16.5) | 9851 |
| Tubal factor | 7896 (25.8) | 2672 (26.8) | 10 568 |
| Unexplained or other factorb | 10 147 (33.1) | 2816 (28.2) | 12 963 |
| Missing | 4377 (14.3) | 2854 (28.6) | 7231 |
| Age at 1st ART treatment or 1st visit to the gynecologist, yc | |||
| <27 | 2457 (8.0) | 1878 (18.8) | 4335 |
| 27-29 | 4920 (16.1) | 2157 (21.6) | 7077 |
| 30-32 | 7941 (25.9) | 2295 (23.0) | 10 236 |
| 33-35 | 7448 (24.3) | 1908 (19.1) | 9356 |
| ≥36 | 7859 (25.7) | 1750 (17.5) | 9609 |
| Year of 1st ART treatment or 1st visit to the gynecologistc | |||
| <1989 | 1818 (5.9) | 3040 (30.4) | 4858 |
| 1989-1992 | 8731 (28.5) | 2977 (29.8) | 11 708 |
| 1993-1996 | 11 633 (38.0) | 2473 (24.8) | 14 106 |
| 1997-2000 | 8443 (27.6) | 1498 (15.0) | 9941 |
| Total No. of ART cycles | |||
| 0 | 0 (0.0) | 9988 (100.0) | 9988 |
| 1-2 | 11 520 (37.6) | 0 (0.0) | 11 520 |
| 3-4 | 10 695 (34.9) | 0 (0.0) | 10 695 |
| 5-6 | 3733 (12.2) | 0 (0.0) | 3733 |
| ≥7 | 2080 (6.8) | 0 (0.0) | 2080 |
| Missing | 2597 (8.5) | 0 (0.0) | 2597 |
| Total No. of IUI and ART cycles | |||
| 0 | 0 (0.0) | 4584 (45.9) | 4584 |
| 1-2 | 8103 (26.5) | 891 (8.9) | 8994 |
| 3-4 | 7,909 (25.8) | 736 (7.4) | 8645 |
| 5-6 | 4009 (13.1) | 503 (5.0) | 4512 |
| ≥7 | 8054 (26.3) | 383 (3.8) | 8437 |
| Missing | 2550 (8.3) | 2891 (28.9) | 5441 |
| Time since 1st treatment, yc | |||
| <10 | 1627 (5.3) | 331 (3.3) | 1958 |
| 10-14 | 866 (2.8) | 270 (2.7) | 1136 |
| 15-19 | 5687 (18.6) | 1240 (12.4) | 6927 |
| 20-24 | 12 433 (40.6) | 2664 (26.7) | 15 097 |
| 25-29 | 8884 (29.0) | 3205 (32.1) | 12 089 |
| ≥30 | 1128 (3.7) | 2278 (22.8) | 3406 |
| Age at end of follow-up, y | |||
| <45 | 2121 (6.9) | 605 (6.1) | 2726 |
| 45-49 | 3444 (11.3) | 1140 (11.4) | 4584 |
| 50-54 | 7902 (25.8) | 2210 (22.1) | 10 112 |
| 55-59 | 9575 (31.3) | 2718 (27.2) | 12 293 |
| ≥60 | 7583 (24.8) | 3315 (33.2) | 10 898 |
| No. of births | |||
| 0 | 10 832 (35.4) | 2517 (25.2) | 13 349 |
| 1 | 9766 (31.9) | 2486 (24.9) | 12 252 |
| ≥2 | 9913 (32.4) | 4844 (48.5) | 14 757 |
| Missing | 114 (0.4) | 141 (1.4) | 255 |
| Age at 1st birth, yd | |||
| <30 | 6390 (20.9) | 3534 (35.4) | 9924 |
| 30-34 | 7526 (24.6) | 2368 (23.7) | 9894 |
| ≥35 | 5720 (18.7) | 1410 (14.1) | 7130 |
| Missing | 43 (0.1) | 18 (0.2) | 61 |
Based on information from medical records if available and on information from questionnaires if no medical record information was available. If several diagnoses had been registered, without mention of the main diagnosis, the following order was applied: male factor, tubal factor, unexplained or other factor (including hormonal factor) for main diagnosis. ART = assisted reproductive technology; IUI = intrauterine insemination.
Other factors include endometriosis and cervical factors and hormonal factors such as ovulation disorders, polycystic ovary syndrome, and premature menopause.
First treatment indicates start of ART treatment for ART group and first visit at gynecologist for the non-ART group.
Only among 27 009 parous women (19 679 ART and 7330 non-ART).