Table 3.
Maternal and infant characteristics for the study population and by cluster units
| Cluster * 1 | Cluster * 2 | Cluster * 3 | P value | ||||
| n=1118 infants | n=398 infants | n=619 infants | |||||
| Maternal characteristics | |||||||
| Maternal age | |||||||
| <25 years | 221/1118 | 19.8 | 67/398 | 16.8 | 111/619 | 17.9 | 0.29 |
| 25 to 34 years | 640/1118 | 57.2 | 248/398 | 62.3 | 353/619 | 57.0 | |
| >35 years | 257/1118 | 23.0 | 83/398 | 20.9 | 155/619 | 25.0 | |
| Birth in France | 879/1100 | 79.9 | 286/394 | 72.6 | 454/615 | 73.8 | 0.002 |
| Parents’ socio-economic status † | |||||||
| Professional | 238/1055 | 22.6 | 97/382 | 25.4 | 122/596 | 20.5 | 0.053 |
| Intermediate | 213/1055 | 20.2 | 82/382 | 21.5 | 129/596 | 21.6 | |
| Administrative, public service, self-employed and students | 288/1055 | 27.3 | 122/382 | 31.9 | 160/596 | 26.8 | |
| Shop assistants and service workers | 132/1055 | 12.5 | 35/382 | 9.2 | 92/596 | 15.4 | |
| Manual workers | 143/1055 | 13.6 | 35/382 | 9.2 | 71/596 | 11.9 | |
| Unknown occupation | 41/1055 | 3.9 | 11/382 | 2.9 | 22/596 | 3.7 | |
| Obstetric factors | |||||||
| Singleton pregnancy | 753/1118 | 67.4 | 269/398 | 67.6 | 406/619 | 65.6 | 0.72 |
| Antenatal steroids | 995/1104 | 90.1 | 359/394 | 91.1 | 531/607 | 87.5 | 0.12 |
| Vaginal delivery | 288/1113 | 25.9 | 136/393 | 34.6 | 169/615 | 27.5 | 0.004 |
| Neonatal characteristics | |||||||
| Gestational age, weeks | |||||||
| 27 | 168/1118 | 15.0 | 47/398 | 11.8 | 87/619 | 14.1 | 0.26 |
| 28 | 185/1118 | 16.5 | 65/398 | 16.3 | 105/619 | 17.0 | |
| 29 | 209/1118 | 18.7 | 74/398 | 18.6 | 113/619 | 18.3 | |
| 30 | 275/1118 | 24.6 | 113/398 | 28.4 | 132/619 | 21.3 | |
| 31 | 281/1118 | 25.1 | 99/398 | 24.9 | 182/619 | 29.4 | |
| Male | 557/1118 | 49.8 | 228/398 | 57.3 | 347/619 | 56.1 | 0.008 |
| Small-for-gestational age ‡ | 445/1118 | 39.8 | 170/398 | 42.7 | 248/619 | 40.1 | 0.58 |
Data are number of events/number in each group and percentage.
*Clusters are defined according to the distribution of care within units using a hierarchical analysis.
†Defined as the highest occupational status of the mother and father, or mother only if living alone.
‡Small-for- gestational age was defined as birth weight less than the 10th percentile for gestational age and sex based on French intrauterine ’ growth curves (Ego 2016).