Exposure-response curves are central to understanding how continuous exposures relate to health outcomes. Common methods to plot such curves include the use of crude and adjusted regression, with the exposure specified using fractional polynomials or regression splines. These approaches are subject to important limitations. In this article, we illustrate the use of semiparametric marginally adjusted exposure-response curves obtained via inverse probability weighting. We explore the relation between interpregnancy interval and preterm birth in a cohort of over 720,000 live births in Quebec between 1989 and 2008. We include online supplementary material showing how mixed modeling routines in standard software packages can be used to implement the procedure, and how pointwise bootstrap confidence intervals can be obtained.