  Infant pose monitoring during sleep has multiple applications in both
healthcare and home settings. In a healthcare setting, pose detection can be
used for region of interest detection and movement detection for noncontact
based monitoring systems. In a home setting, pose detection can be used to
detect sleep positions which has shown to have a strong influence on multiple
health factors. However, pose monitoring during sleep is challenging due to
heavy occlusions from blanket coverings and low lighting. To address this, we
present a novel dataset, Simultaneously-collected multimodal Mannequin Lying
pose (SMaL) dataset, for under the cover infant pose estimation. We collect
depth and pressure imagery of an infant mannequin in different poses under
various cover conditions. We successfully infer full body pose under the cover
by training state-of-art pose estimation methods and leveraging existing
multimodal adult pose datasets for transfer learning. We demonstrate a
hierarchical pretraining strategy for transformer-based models to significantly
improve performance on our dataset. Our best performing model was able to
detect joints under the cover within 25mm 86% of the time with an overall mean
error of 16.9mm. Data, code and models publicly available at
https://github.com/DanielKyr/SMaL
