Table 1. Demographic characteristics of the study population.
| Pre-universal 36-week scan | Post-universal 36-week scan | |
|---|---|---|
| N (total) | 15,371 | 14,188 |
| Deliveries ≥24 and <37 weeks, n (%) | 923 (6.0) | 802 (5.7) |
| Breech at delivery <37 weeks, n (%) | 107 (0.7) | 110 (0.8) |
| Deliveries ≥37 and <43 weeks, n (%) | 14,444 (94.0) | 13,381 (94.3) |
| Deliveries ≥43 weeks, n (%) | 4 (0.03) | 5 (0.04) |
| Maternal age (years), mean ± SD | 30.8 (5.5) | 31.1 (5.4) |
| Body mass index (kg/m2), mean ± SD | 25.4 (5.5) | 25.7 (5.6) |
| Nulliparous, n (%) | 6,699 (43.6) | 6,271 (44.2) |
| Parity >3, n (%) | 386 (2.5) | 315 (2.2) |
| White ethnicity, n (%) | 12,143 (79.0) | 11,274 (79.5) |
| Gestational age at delivery (weeks), mean ± SD | 39.6 (2.0) | 39.7 (2.0) |
| Male fetus, n (%) | 7,912 (51.5) | 7,345 (51.8) |
| Birthweight (g), mean ± SD | 3,434.7 (586.7) | 3,446.3 (590.9) |
| Ultrasound scan ≥35+0 weeks among term deliveries, n (%) | 5578 (38.6) | 13251 (99.0) |
*p-Value from t test or Pearson chi-squared test, as appropriate.
Missing data were 2% for body mass index and 7.8% for maternal ethnicity; <2% otherwise.