It took artists awhile to figure out a way to depict a full grown man lying on his mother without it being painfully awkward looking, as evidenced in the medieval Pietàs above. Michelangelo, with his brilliance at handling complicated compositions, buffs up the Virgin with flowing robes so she can be large enough to hold her son in her lap while still retaining her graceful appearance.
Unknown, Pietà, c.1330
Unknown, Křivákova Pietà, 1390-1400
Unknown, Pietà, c.1400 Bohemian
Michelangelo Buonarroti, Pietà, 1498–1499