Comparison of demographic and prenatal characteristics of study subjects between periods
| Period 1 n = 1479 | Period 2 n = 1839 | Mean difference (95% CI) | P value | |||
| Maternal age, mean (SD) | 30.7 (5.3) | n=1413 | 31.2 (5.4) | n=1803 | 0.56 (0.19 to 0.94) | 0.003 |
| Birth weight, mean (SD) | 597 (108) | n=1479 | 591 (111) | n=1839 | −5.6 (−13.1 to 1.9) | 0.142 |
| GA, mean (SD) | 23.8 (0.7) | n=1479 | 23.8 (0.7) | n=1839 | −0.03 (−0.08 to 0.02) | 0.235 |
| GA distribution (weeks) | 0.091 | |||||
| 22 | 183/1479 | 12.4% | 271/1839 | 14.7% | ||
| 23 | 544/1479 | 36.8% | 686/1839 | 37.3% | ||
| 24 | 752/1479 | 50.8% | 882/1839 | 48.0% | ||
| Male | 784/1478 | 53.0% | 933/1837 | 50.8% | 0.208 | |
| Multiple births | 292/1479 | 19.7% | 300/1839 | 16.3% | 0.011 | |
| Congenital anomalies | 41/1479 | 2.8% | 53/1806 | 2.9% | 0.834 | |
| Pregnancy-related hypertension | 76/1479 | 5.1% | 124/1833 | 6.8% | 0.056 | |
| Clinical CAM | 494/1479 | 33.4% | 649/1758 | 36.9% | 0.039 | |
| Antenatal steroids | 533/1479 | 36.0% | 969/1817 | 53.3% | <0.001 | |
| Caesarean section | 819/1479 | 55.4% | 1140/1833 | 62.2% | <0.001 |
Values are the number/number of measurements and percentage unless otherwise stated. Mean difference (95% CIs) for period 2 versus period 1.
CAM, chorioamnionitis; GA, gestational age.