We present a study of the evolution of late-type field dwarfs over the last 1.5 Gyr, based on HST ACS observations carried out as part of the GEMS survey. This study is amongst the first to probe the evolution of dwarfs over such a large timescale. The comparison of structural properties, particularly size and scale length, indicates that the dwarfs in the redshift range $z \sim$ 0.01 to 0.15 (look-back times up to 1.8 Gyr) are more extended than local dwarfs. We argue that this difference is due to the star formation activity becoming more centrally concentrated in late-type dwarfs over the last ${\sim} 1.5$ Gyr. We discuss several possible causes for this evolution. We also find a lack of blue compact dwarfs in the GEMS sample and interpret this as indication of the fact that strong, centrally concentrated star formation is a feature of evolved dwarfs that are entering their final stages of evolution.