When Benedict XVI became the first pope to resign in 600 years it sent shockwaves through the Catholic Church. Now, after spending two weeks in hospital battling pneumonia, the speculation in the Vatican is whether his successor Pope Francis might do the same.

With Pope Francis' health concerns mounting, discussions within the Vatican suggest he may consider stepping down—an event that would mark only the third papal resignation in over 600 years.

On Saturday, the Vatican secretary of state, Cardinal Pietro Parolin, took Francis’ place to celebrate Mass for an anti-abortion group. On Sunday, another Vatican official, Cardinal Michael Czerny, is stepping in for the pope to celebrate a Holy Year Mass for volunteers.