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Relationship between BMI and risk of SAB <22 weeks fitted by restricted cubic splines.
Notes: Reference level for the hazard ratio is a BMI of 22 kg/m2. The dotted lines represent the corresponding 95% confidence intervals. Four knots at 19.5, 21.3, 25.4, and 30.5 kg/m2. The curve is adjusted for maternal age, smoking, parity, vocational training/education, physical activity, and alcohol and caffeine consumption.
