Based on the memoirs of Jennifer Worth, the BBC One period drama has been a ratings smash hit, pulling in huge audiences on Sunday nights.
Its first series was BBC One's biggest drama launch on over a decade, while the second series had a consolidated average audience of over ten million. It is the highest-rated drama of the year so far on any channel.
Jessica Raine, Miranda Hart, Helen George and Pam Ferris lead the cast.
The show will return for a Christmas special and a third series in early 2014.
Series three will kick off in 1959 on the eve of the swinging '60s, and "the winds of change are sweeping through the country and the residents of Nonnatus House".
It will have an all-female director lineup for