Table 3 Adjusted odds ratios and 95% confidence intervervals for the associations between gestational weight gain and preterm birth categories overall and within strata of body mass index

Very Preterm

  Low

1.84 (1.71, 1.97)

2.08 (1.66, 2.61)

2.07 (1.88, 2.29)

1.73 (1.47, 2.04)

1.44 (1.21, 1.72)

  Adequate

Ref

Ref

Ref

Ref

Ref

  Excessive

0.94 (0.88, 1.00)

0.91 (0.69, 1.21)

1.05 (0.95, 1.16)

0.90 (0.79, 1.04)

0.95 (0.83, 1.10)

Moderately Preterm

  Low

1.50 (1.40, 1.61)

1.84 (1.48, 2.29)

1.61 (1.46, 1.77)

1.31 (1.11, 1.56)

1.24 (1.03, 1.51)

  Adequate

Ref

Ref

Ref

Ref

Ref

  Excessive

0.83 (0.78, 0.89)

0.82 (0.62, 1.09)

0.93 (0.84, 1.02)

0.77 (0.67, 0.88)

0.96 (0.82, 1.11)

Late Preterm

  Low

1.28 (1.24, 1.31)

1.47 (1.36, 1.59)

1.33 (1.28, 1.38)

1.25 (1.17, 1.33)

0.93 (0.87, 1.01)

  Adequate

Ref

Ref

Ref

Ref

Ref

  Excessive

1.00 (0.97, 1.02)

0.99 (0.89, 1.10)

1.06 (1.02, 1.10)

1.00 (0.95, 1.05)

0.93 (0.88, 0.98)