GA categories and the distribution of singleton births throughout the study periods (12 March–14 April 2015–2020); the distribution of births permille, by GA category for the lockdown period (12 March–14 April 2020) compared with consolidated data from 12 March–14 April 2015–2019
| GA | 2015 | 2016 | 2017 | 2018 | 2019 | 2020 | Prevalence (permille) | OR | 95% CI | P value | |||
| Weeks+days | Mean (SD) | N (%) | N (%) | N (%) | N (%) | N (%) | N (%) | 2015–2019 (SD) | 2020 | ||||
| Extremely premature | ≤27+6 | 25.7 (1.31) | 13 (0.27) | 9 (0.17) | 9 (0.17) | 13 (0.24) | 13 (0.25) | 1 (0.02) | 2.19 (0.47) | 0.19 | 0.09 | 0.01 to 0.40 | <0.001 |
| Very premature | 28+0–31+6 | 29.7 (1.07) | 27 (0.56) | 32 (0.60) | 31 (0.59) | 28 (0.52) | 27 (0.52) | 32 (0.62) | 5.57 (0.36) | 6.20 | 1.11 | 0.75 to 1.61 | 0.589 |
| Moderate/late premature | 32+0–36+6 | 34.9 (1.26) | 203 (4.19) | 224 (4.20) | 235 (4.44) | 215 (3.98) | 238 (4.62) | 216 (4.18) | 42.85 (2.45) | 41.84 | 0.98 | 0.84 to 1.13 | 0.742 |
| Term | 37+0–41+6 | 39.6 (1.15) | 4512 (93.20) | 4936 (92.59) | 4914 (92.82) | 5023 (93.05) | 4752 (92.20) | 4810 (93.18) | 927.70 (3.96) | 931.81 | 1.06 | 0.95 to 1.20 | 0.293 |
| Late term | ≥42+0 | 42.0 (0.16) | 86 (1.78) | 130 (2.44) | 105 (1.98) | 119 (2.20) | 124 (2.41) | 103 (2.00) | 21.68 (2.82) | 19.95 | 0.92 | 0.74 to 1.13 | 0.430 |
| Total | all births | 39.4 (1.81) | 4841 (100) | 5331 (100) | 5294 (100) | 5398 (100) | 5154 (100) | 5162 (100) | 1000 | 1000 | |||
GA, gestational age.