Lighting for infant portraits
Try exposing for the subject (baby) alone (use spot / center-weighted metering). If the baby is dressed lighter than black cloth, the black cloth will then under-expose (appear dark black). If the baby is dressed darker than a white cloth, the cloth may blow-out (go really white). Usually our 'average' meter setting will do just that -average-out everything in the scene. Darks try to brighten and brights darken, as the camera attempts to bring everything to 'grey'.