From the case:
Meconium aspiration
Frontal

Widespread granular airspace opacities without effusion or pneumothorax.
Case Discussion
There are no humeral head ossification centers, which may push you towards a preterm neonate and RDS. Don't be fooled though - look at the lung volumes and realize that they are not decreased. This all but completely excludes the possibility of RDS.
Features here are representative of meconium aspiration.