Baseline and obstetric characteristics of the study subjects (n=164 107)
| Characteristic | 2020 (n=24 312) | 2014–2019 (n=139 795) |
| Maternal age, years—% | ||
| ≥35.0 | 18.8 | 16.1 |
| 25.0~34.9 | 78.6 | 80.0 |
| <25.0 | 2.6 | 3.9 |
| Insurance—% | 73.4 | 71.3 |
| Married—% | 99.2 | 99.2 |
| Nulliparity—% | 73.9 | 74.8 |
| BMI at first prenatal visit—% | ||
| ≥30.0 | 1.8 | 1.5 |
| 25.0–29.9 | 12.5 | 11.9 |
| 20.0–24.9 | 57.3 | 57.8 |
| <20.0 | 28.4 | 28.8 |
| Education—years (mean±SD) | 15.3±2.8 | 14.9±2.6 |
| Assisted conception—% | 2.9 | 3.2 |
| DM and GDM—% | 11.3 | 12.3 |
| Hypertensive disorders—% | 5.8 | 5.4 |
| ICP—% | 1.2 | 1.0 |
| Gestational age at delivery—% | ||
| <32 GW | 0.5 | 0.7 |
| 32–36 GW | 4.7 | 4.7 |
| ≥37 GW | 94.8 | 94.6 |
| Stillbirth—% | 0.2 | 0.2 |
| Birth weight—% | ||
| Large for gestational age | 4.7 | 4.5 |
| Average for gestational age | 92.4 | 92.3 |
| Small for gestational age | 2.9 | 3.2 |
| Delivery mode—% | ||
| Spontaneous delivery | 54.5 | 60.6 |
| Assisted vaginal delivery | 1.5 | 1.3 |
| Caesarean delivery | 44.0 | 38.1 |
BMI, body mass index; DM, pregestational diabetes; GDM, gestational diabetes; GW, gestational week; ICP, intrahepatic cholestasis of pregnancy.