Characteristics of the study population
| N=1020, n (%) | |
| Distribution of women according to the level of perinatal care of maternity unit of delivery | |
| 1 | 91 (9) |
| 2 | 268 (26) |
| 3 | 661 (65) |
| Women with a French nationality | 750 (74) |
| Married or cohabiting women (vs not living with partner) | 824 (81) |
| Age of the mother (years)* | 28.9 (5.9) |
| Multipara | 455 (45) |
| Regular antenatal care during pregnancy | 837 (82) |
| Pregnancy after assisted reproductive technology | 84 (8) |
| Cause of preterm birth | |
| Preterm labour | 512 (50) |
| Preterm premature rupture of membranes | 351 (35) |
| Hypertensive disorders without fetal growth restriction | 11 (1) |
| Hypertensive disorders with fetal growth restriction | 23 (2) |
| Placental abruption | 11 (1) |
| Fetal growth restriction without hypertensive disorders | 70 (7) |
| Gestational age of birth (weeks)* | 24.1 (1.4) |
| Birth weight in grams | |
| <500 | 195 (19) |
| 500–600 | 181 (18) |
| 600–700 | 161 (16) |
| >700 | 441 (43) |
| Female newborn | 451 (44) |
*Mean (SD).