Age (four categories)
0 = ≤24
1 = 25~29
2 = 30~34
3 = ≥35

Ethnicity
1 = Han
2 = Other

Educational level
1 = Below high school
2 = 大专本科
3 = Postgraduate

International standard for BMI before pregnancy (four categories)
0 = 18.5~24.9
1 = <18.5
2 = 25.0~29.9
3 = ≥30.0

Pre-pregnancy BMI (four categories) Chinese standard
0 = 18.5~23.9
1 = <18.5
2 = 24.0~27.9
3 = ≥28.0

Family wealth index
1 = Poor
2 = Moderate
3 = Rich

Parity
0 = Nulliparous
1 = Multiparous

Cold/fever before or during pregnancy
0 = No
1 = Yes

Fetal sex
1 = Male
2 = Female

Low birth weight
0 = ≥2500
1 = <2500

macrosomia
0 = <4000
1 = ≥4000

Macrosomia classification
0 = <4000
1 = 4000-4499
2 = 4500-4999
3 = ≥5000