Sleep variable Total PTB PTB
Model 1 Model 1 Model 2 Model 2 Model 3 Model 3
OR (95% CI) OR (95% CI) OR (95% CI)
Changes in sleep quality during pregnancy a Changes in sleep quality during pregnancy a
Always good Always good 3888 (71.8) 1 1 1
Always poor Always poor 326 (6.0) 1.09 (0.62,1.90) 1.09 (0.62,1.92) 1.05 (0.59,1.84)
From good to poor From good to poor 684 (12.6) 1.15 (0.78,1.71) 1.19 (0.80,1.77) 1.20 (0.80,1.78)
From poor to good From poor to good 514 (9.5) 1.24 (0.80,1.91) 1.25 (0.81,1.94) 1.27 (0.82,1.97)
Changes in sleep duration during pregnancy b Changes in sleep duration during pregnancy b
Always good Always good 1745 (32.2) 1 1 1
Always poor Always poor 1436 (26.5) 0.97 (0.67,1.39) 0.98 (0.47,1.43) 1.98 (0.68,1.43)
From good to poor From good to poor 856 (15.8) 1.13 (0.75,1.69) 1.14 (0.76,1.72) 1.14 (0.75,1.71)
From poor to good From poor to good 1375 (25.4) 1.15 (0.81,1.63) 1.15 (0.80,1.63) 1.17 (0.82,1.67)
Changes in napping during pregnancy c Changes in napping during pregnancy c
Always good Always good 2867 (53.0) 1 1 1
Always poor Always poor 153 (2.8) 0.64 (0.23,1.77) 0.61 (0.22,1.67) 0.59 (0.21,1.64)
From good to poor From good to poor 2237 (41.3) 1.12 (0.85,1.47) 1.14 (0.86,1.50) 1.15 (0.87,1.53)
From poor to good From poor to good 155 (2.9) 0.80 (0.32,1.98) 0.76 (0.30,1.86) 0.74 (0.30,1.87)