Table 3 Predictive factors for intrapartum caesarean section among women with a trial of labour for a planned vaginal birth, NSW, 2007–2011. Two models were fitted progressively adjusting for case-mix and hospital factors

Maternal age (years)

1.02 (1.01, 1.03)

1.02 (1.02, 1.03)

Country of birth

 Australia or New Zealand

1.00

1.00

 Europe or North America

0.86 (0.74, 1.00)

0.86 (0.74, 1.00)

 Other

1.17 (1.06, 1.29)

1.17 (1.06, 1.29)

Smoking

1.15 (1.03, 1.29)

1.14 (1.02, 1.29)

Diabetes (pre-existing or gestational)

1.27 (1.10, 1.46)

1.27 (1.10, 1.46)

Hypertensive disorders

1.31 (1.12, 1.53)

1.31 (1.12, 1.53)

Other chronic medical conditions^a

1.95 (1.38, 2.73)

1.93 (1.37, 2.71)

Parity 2 or more (versus parity 1)

0.70 (0.63, 0.78)

0.70 (0.63, 0.78)

Labour/vaginal birth prior to index caesarean

0.48 (0.42, 0.56)

0.48 (0.42, 0.55)

Previous vaginal birth after caesarean

0.16 (0.14, 0.19)

0.16 (0.14, 0.19)

Previous perinatal death

1.80 (1.32, 2.46)

1.79 (1.31, 2.44)

Non-CS uterine scar

2.78 (1.41, 5.48)

2.75 (1.39, 5.44)

Assisted reproductive technology use (last 12 months)

0.55 (0.44, 0.68)

0.55 (0.45, 0.68)

Inter-pregnancy interval (months)

 0-17

0.92 (0.85, 1.00)

0.92 (0.85, 1.00)

 18-59

1.00

1.00

 60+

1.22 (1.06, 1.40)

1.21 (1.06, 1.40)

 Unknown

0.83 (0.74, 0.92)

0.82 (0.74, 0.92)

Placental conditions^b

4.26 (3.22, 5.65)

4.26 (3.22, 5.65)

Estimated gestational age (weeks)

 37

1.58 (1.37, 1.82)

1.58 (1.38, 1.82)

 38

1.30 (1.18, 1.44)

1.30 (1.18, 1.45)

 39

1.00

1.00

 40

0.94 (0.86, 1.03)

0.94 (0.86, 1.03)

 41+

1.41 (1.26, 1.58)

1.41 (1.26, 1.57)

Large for gestational age (>90^th percentile)

1.71 (1.53, 1.90)

1.71 (1.53, 1.91)

Stillbirth

0.26 (0.11, 0.62)

0.25 (0.10, 0.62)

Repeat caesarean rate after nulliparous breech caesarean (Propensity towards vaginal birth after caesarean section)

-

1.04 (1.02, 1.07)

Instrumental delivery rate

-

0.82 (0.71, 0.93)