Quantile differences in estimated fetal weight across gestational weeks between smokers and non-smokers at the 25th, 50th, and 75th percentiles in a validation sub-sample of 8,517 pregnancies (13,354 ultrasound visits) at the Magee-Womens Hospital, University of Pittsburgh Medical Center, Pittsburgh, PA, 2010–2013. Plot with grey background represents quantile differences estimated using actual fetal weight estimates. Plots with white backgrounds represent quantile differences estimated using predicted fetal weight estimates. Translucent lines represent fits from 100 bootstrap resamples.