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. Author manuscript; available in PMC: 2018 Jul 1.

Published in final edited form as: Am J Obstet Gynecol. 2017 Mar 9;217(1):80.e1–80.e8. doi: 10.1016/j.ajog.2017.03.002

Figure 2A. Spline regression model for preterm birth <34 weeks gestational age

Figure 2B. Spline regression model for preterm birth <37 weeks gestational age

The solid line demonstrates the estimated risk for preterm birth within the regression models at <34 and <37 weeks gestational age with knot locations at maternal ages of 19 (4^th percentile of the age distribution), 24 (21^st percentile), 27 (35^th percentile), 30 (53^rd percentile), 33 (71^st percentile), 36 (86^th percentile), and 42 (98^th percentile). The dashed lines represent the upper and lower bounds of the 95% confidence interval.

Figure 2A. Spline regression model for preterm birth <34 weeks gestational age

Figure 2B. Spline regression model for preterm birth <37 weeks gestational age

The solid line demonstrates the estimated risk for preterm birth within the regression models at <34 and <37 weeks gestational age with knot locations at maternal ages of 19 (4^th percentile of the age distribution), 24 (21^st percentile), 27 (35^th percentile), 30 (53^rd percentile), 33 (71^st percentile), 36 (86^th percentile), and 42 (98^th percentile). The dashed lines represent the upper and lower bounds of the 95% confidence interval.