Table 2 Baseline characteristics of participations after the propensity score matched

Age^a

32.00 (29.00,35.00)

32.00 (29.00,35.00)

−0.279

0.781

Gestational age (weeks)^a

39.57 (38.86,40.29)

39.57 (38.86,40.29)

−0.032

0.975

Gravidity^a

2.00 (2.00,3.00)

2.00 (2.00,3.00)

−1.477

0.140

Parity^a

1.00 (0.00,1.00)

1.00 (0.00,1.00)

1.171

0.242

Maternal height (cm) ^a

163.00 (160.00,167.60)

163.80 (160.00,167.60)

−0.965

0.335

Maternal BMI (kg/(m)²)^a

28.47 (25.77,32.01)

28.56 (26.10,32.13)

−4.317

< 0.001

Baby height (cm) ^a

50.20 (48.30,52.00)

50.50 (48.30,52.10)

−0.989

0.323

KBaby weight (kg) ^a

3.37 (3.07,3.65)

3.35 (3.08,3.64)

−0.071

0.943

Preterm delivery^b

130 (4.3%)

103 (3.4%)

3.253

0.071

Multiple pregnancy^b

12 (0.4%)

11 (0.4%)

0.044

0.835

Induction^b

469 (15.4%)

431 (14.1%)

1.882

0.170

Oxytocin^b

626 (20.5%)

597 (19.5%)

0.860

0.354

Operative delivery^b

49 (1.6%)

58 (1.9%)

0.771

0.380

Ethnic^b

7.212

0.027

 White

1984 (65.0%)

2083 (68.2%)

 Black

229 (7.5%)

208 (6.8%)

 others

841 (27.5%)

763 (25.0%)