It has occasionally been suggested that Clairmont was also the mother of a daughter fathered by Percy Shelley. The possibility goes back to the accusation by Shelley's servants, Elise and Paolo Foggi, that Clairmont gave birth to Shelley's baby during a stay in Naples, where on 27 February 1819, Shelley registered a baby named Elena Adelaide Shelley as having been born on 27 December 1818. The registrar recorded her as the daughter of Percy Shelley and "Maria" or "Marina Padurin" (possibly an Italian mispronunciation of "Mary Godwin"), and she was baptized the same day as the lawfully begotten child of Percy Shelley and Mary Godwin. It is, however, almost impossible that Mary Shelley was the mother, and this has given rise to several theories, including that the child was indeed Clairmont's.Seymour, p. 221; Holmes, pp. 460–474; Bieri, pp. 103–112; Gittings and Manton, p. 46; Journals of Mary Shelley, pp. 249–250 n3. Among several theories, some scholars have speculated she was Elise Foggi, a nursemaid of the Shelley family; others believe Elena's mother was Clairmont. Thomas Medwin, a cousin of Shelley, claimed the mother was an unnamed woman with whom Shelley had an affair. It has also been proposed that Shelley adopted a local child as his own, or that the child was Elise Foggi's by Byron. Clairmont herself had ascended Mount Vesuvius, carried on a palanquin, on 16 December 1818, only nine days before the date given for the birth of Elena.Seymour, p. 224. Though, since the question arises of why Shelley waited two months before registering the baby, the birth date may not be reliable. It may be significant, however, that Clairmont was taken ill at about the same time – according to Mary Shelley's journal she was ill on 27 December – and that her journal of June 1818 to early March 1819 has been lost.Gittings and Manton, p. 45; Bieri, p. 104. Bieri calls the loss of the journal "significant and probably not accidental" and part of a situation in which "the Shelley family was concealing much that occurred in Naples". In a letter to Isabella Hoppner of 10 August 1821, Mary Shelley, however, stated emphatically that "Claire had no child". She also insisted:
