Table 4 Hazard ratios by parity or calving season

 1

Reference

Reference

Reference

Reference

 2

1.66 (1.46–1.90)

2.99 (2.35–3.81)

NS^b

NS^b

 3

2.14 (1.88–2.44)

4.36 (3.44–5.52)

2.65 (1.80–3.89)

1.68 (1.24–2.29)

 4

2.03 (1.76–2.34)

4.48 (3.50–5.74)

2.79 (1.86–4.20)

NS^b

  ≥ 5

2.13 (1.86–2.45)

4.86 (3.81–6.19)

3.94 (2.68–5.78)

NS^b

 Spring

NS^b

0.85 (0.73–0.99)

NS^b

NS^b

 Summer

0.80 (0.69–0.93)

1.91 (1.42–2.58)

1.55 (1.18–2.04)

 Autumn

0.81 (0.70–0.94)

NS^b

NS^b

 Winter

Reference

Reference

Reference