Table 1. Descriptive Characteristics of Participants by Preterm Birth.
| Characteristic | Participants, No. (%) | ||
|---|---|---|---|
| Total (N = 1427) | No preterm birth (n = 1347) | Preterm birth (n = 80) | |
| Moderate-to-vigorous intensity physical activity, mean (SD), min/d | 84.0 (38.1) | 84.5 (38.0) | 75.5 (40.2) |
| Fraction of physical activity energy expenditure accumulated from moderate-to-vigorous intensity physical activity, mean (SD), % | 33.0 (10.2) | 33.2 (10.1) | 29.7 (11.2) |
| Physical activity energy expenditure, mean (SD), kJ kg–1 d–1 | 43.8 (10.9) | 43.9 (10.8) | 42.3 (12.3) |
| Accelerometer wear time, mean (SD), d | 11.4 (2.3) | 11.4 (2.3) | 11.3 (2.8) |
| Age, mean (SD), y | 31.3 (3.8) | 31.2 (3.8) | 32.0 (4.1) |
| Gestational age at baseline, mean (SD), wk | 25.9 (1.9) | 25.9 (1.9) | 25.8 (2.3) |
| Prepregnancy body mass index, mean (SD)a | 22.3 (3.6) | 22.2 (3.6) | 22.5 (3.8) |
| Primiparity | 911 (63.8) | 857 (63.6) | 54 (67.5) |
| Pregnant with twins | 16 (1.1) | 7 (0.5) | 9 (11.3) |
| Pregnant with preeclampsia | 36 (2.5) | 30 (2.2) | 6 (7.5) |
| Pregnant with medication treatment | 15 (1.1)b | 12 (0.9) | 3 (3.8) |
| Pregnant with history of preterm birth | 18 (1.3) | 13 (0.97) | 5 (6.3) |
| Education | |||
| High school or vocational school | 164 (11.5) | 155 (11.5) | 9 (11.3) |
| University or professional school | 1053 (73.8) | 998 (74.1) | 55 (68.8) |
| Greater than university | 210 (14.7) | 194 (14.4) | 16 (20.0) |
| Annual household income, ¥c | |||
| <100 000 | 339 (23.8) | 317 (23.5) | 22 (27.5) |
| 100 000-200 000 | 552 (38.7) | 529 (39.3) | 23 (28.7) |
| >200 000 | 536 (37.6) | 501 (37.2) | 35 (43.8) |
| Current smoking | 50 (3.5) | 45 (3.3) | 5 (6.3) |
| Current drinking | 43 (3.0) | 41 (3.0) | 2 (2.5) |
| Recruitment after COVID-19 | |||
| No | 224 (15.7) | 211 (94.2) | 13 (5.8) |
| Yes | 1203 (84.3) | 1136 (94.4) | 67 (5.6) |
a
Body mass index is calculated as weight in kilograms divided by height in meters squared.
b
Among the included participants, 11 were treated with metformin and 4 were treated with insulin.
c
As of November 8, 2024, ¥1.00 = US $0.14.