Table. Characteristics of Episodes of Included Participantsa.
| Characteristic | Episodes, No. (%) | ||||
|---|---|---|---|---|---|
| Time to pregnancy | Miscarriage | ||||
| Women (n = 3033)b | Men (n = 2288) | Women (n = 2770)c | Men (n = 2189) | ||
| Age at enrollment, median (IQR), y | 31.6 (29.2-34.5) | 33.4 (30.5-36.8) | 31.5 (28.9-34.3) | 33.5 (30.4-36.8) | |
| <30 y | 983 (32.4) | 495 (21.7) | 952 (34.4) | 498 (22.8) | |
| 30-35 y | 1382 (45.6) | 944 (41.3) | 1258 (45.5) | 875 (40.0) | |
| >35 y | 668 (22.0) | 847 (37.1) | 560 (20.2) | 814 (37.2) | |
| Missing | 0 | 2 (0.1) | 0 | 2 (0.1) | |
| Ethnicity | |||||
| Dutch | 1875 (62.1) | 1506 (66.3) | 1620 (63.2) | 1370 (66.1) | |
| Other non-Westernd | 268 (8.9) | 208 (9.2) | 224 (8.7) | 193 (9.3) | |
| Other Westerne | 874 (29.0) | 558 (24.6) | 719 (28.1) | 511 (24.6) | |
| Missing | 16 (0.5) | 16 (0.7) | 207 (7.5) | 115 (5.3) | |
| Educational level | |||||
| No education finished, primary education finished, or secondary education finished | 847 (28.3) | 778 (34.2) | 721 (28.3) | 713 (34.3) | |
| Higher education finished | 2151 (71.7) | 1497 (65.8) | 1823 (71.7) | 1365 (65.7) | |
| Missing | 35 (1.2) | 13 (0.6) | 226 (8.2) | 111 (5.1) | |
| BMI, median (IQR) | 23.5 (21.2-26.5) | 24.9 (23.0-27.4) | 23.5 (21.3-26.7) | 25.0 (23.0-27.5) | |
| Underweight (<18.5) | 97 (3.2) | 17 (0.7) | 71 (2.6) | 17 (0.8) | |
| Normal weight (18.5-24.9) | 1860 (61.3) | 1141 (49.9) | 1688 (60.9) | 1081 (49.4) | |
| Overweight (25-29.9) | 711 (23.4) | 881 (38.5) | 655 (23.6) | 838 (38.3) | |
| Obesity (≥30) | 365 (12.0) | 249 (10.9) | 356 (12.9) | 253 (11.6) | |
| Missing | 0 | 0 | 0 | 0 | |
| Smoking | |||||
| No | 1568 (55.4) | 1148 (50.9) | 1249 (55.2) | 1014 (50.7) | |
| Quit smoking before pregnancy | 886 (31.3) | 705 (31.3) | 679 (30.0) | 634 (31.7) | |
| Smoked during pregnancy | 375 (13.3) | 401 (17.8) | 333 (14.7) | 352 (17.6) | |
| Missing | 204 (6.7) | 34 (1.5) | 509 (18.4) | 189 (8.6) | |
| Alcohol consumption | |||||
| No consumption <3 mo before pregnancy | 619 (21.0) | 266 (11.8) | 527 (21.6) | 227 (11.4) | |
| Consumption <3 mo before pregnancy | 1905 (64.6) | 1984 (88.2) | 1502 (61.5) | 1771 (88.6) | |
| Consumption during pregnancy | 427 (14.5) | NA | 412 (16.9) | NA | |
| Missing | 82 (2.7) | 38 (1.7) | 329 (11.9) | 191 (8.7) | |
| Parity | |||||
| Nulliparous | 1945 (65.7) | 1509 (66.9)f | 1575 (63.9) | 1358 (66.7) | |
| Multiparous | 1014 (34.3) | 745 (33.1)f | 891 (36.1) | 678 (33.3) | |
| Missing | 74 (2.4) | 34 (1.5)f | 304 (11.0) | 153 (7.0) | |
| Miscarriage in previous pregnancy | |||||
| No | 2227 (79.2) | 1697 (80.7)f | 1780 (79.8) | 1496 (81.0)f | |
| Yes | 584 (20.8) | 406 (19.3)f | 450 (20.2) | 352 (19.0)f | |
| Missing | 222 (7.3) | 185 (8.1)f | 540 (19.5) | 341 (15.6)f | |
| Time to pregnancy, median (95% range [2.5%-97.5%]), mog | 3.7 (0.0-68.3) | 3.3 (0.0-59.5)f | 3.6 (0.0-65.3) | 3.3 (0.0-56.6)f | |
| ≤12 mo | 1944 (64.1) | 1692 (74.0)f | 1647 (70.2) | 1459 (74.3)f | |
| >12 moh | 541 (17.8) | 382 (16.7)f | 435 (18.5) | 319 (16.2)f | |
| ART leading to pregnancyh | 287 (9.5) | 214 (9.4)f | 245 (10.5) | 186 (9.5)f | |
| Not pregnanth | 261 (8.6) | 0f | NA | 0f | |
| Missing | 0 | 0f | 443 (16.0) | 225 (10.3)f | |
| Occurrence of miscarriage | |||||
| Miscarriage | 219 (7.9) | 135 (5.9)f | 314 (11.3) | 174 (7.9)f | |
| No miscarriage | 2553 (92.1) | 2153 (94.1)f | 2456 (88.7) | 2015 (92.1)f | |
| Missing | 261 (8.6) | 0f | 0 | 0f | |
| Timing of miscarriage, median (IQR), wk | 8.1 (7.0-9.4) | 8.6 (7.6-9.6)f | 8.3 (7.1-9.5) | 8.6 (7.9-9.6)f | |
| First trimester | 201 (92.6) | 122 (91.0)f | 284 (92.2) | 158 (91.9)f | |
| Second trimester | 16 (7.4) | 12 (9.0)f | 24 (7.8) | 14 (8.1)f | |
| Missing | 2 (0.9) | 1 (0.7)f | 6 (1.9) | 2 (1.1)f | |
Abbreviations: ART, assisted reproductive technology; BMI, body mass index (calculated as weight in kilograms divided by height in meters squared); NA, not applicable.
Total study population consisting of 3604 unique women from Rotterdam, the Netherlands, with a total of 4036 participant episodes, leading to 3577 pregnancy episodes. Women were included in preconception and pregnancy between 2017 and 2021.
Study population of time to pregnancy consisting of 2856 unique women from Rotterdam, the Netherlands, with a total of 3033 episodes.
Study population of miscarriage consisting of 2507 unique women with a total of 2770 pregnancy episodes.
Included African; American, non-Western; Asian, non-Western; Chinese; or Indonesian.
Included American, Western; Asian, Western; Cape Verdean; Dutch Antilles; European; German; Yugoslav; Moroccan; Oceanian; Polish; Surinamese; or Turkish.
Parity, miscarriage in previous pregnancy, time to pregnancy in months, occurrence of miscarriage, and timing of miscarriage in weeks in men were derived from their partner.
Time to pregnancy in months was derived from pregnancy episodes with a natural conception.
Episodes with ART leading to pregnancy (n = 287), episodes without pregnancy and use of ART (7 of 261 episodes), and episodes without pregnancy and duration of actively pursuing pregnancy of more than 12 months (218 of 261 episodes) were added to the subfertile group (time to pregnancy >12 months and use of ART) in the analysis.