The shape of the association is shown for entire pregnancy(Fig. 1A) and first trimester (Fig. 1B) PM10 exposure among term births. Online supplementary Figures S1 and S2 display the ex- posure–response curves for the other pregnancy windows and gestational age groups. The decrease in slope above the breakpoint was significant for all time windows among term births, and for the time windows two weeks around conception and second tri- mester among moderately preterm births. Estimates for the sig- nificant breakpoints varied from 29.8 to 40.5 mg/m3.