<P> The second series began on 20 January 2013, and during the run BBC Controller for Drama Ben Stephenson announced that he had commissioned a 2013 Christmas special and a third series of eight episodes to be broadcast in 2014, despite the fact that all the original source material had been exhausted by the end of the second series . The series has also achieved success outside the UK . In the United States, the first series' transmission on PBS in the autumn of 2012 drew an average audience of three million viewers . This figure was 50% higher than the network's primetime average for the 2011--12 season . </P> <P> In December 2015, BBC director general Tony Hall announced that the series had already been commissioned for a 2016 Christmas special and a sixth series, set to consist of eight episodes . The Christmas special was set in a missionary hospital in South Africa, and subsequent episodes would see the characters adapting after their return to Poplar as they move into 1962 . In November 2016, the BBC announced it has commissioned three further series and Christmas specials, through to a ninth series in 2020, moving the plot into the mid-sixties . As of 12 March 2017, 51 episodes of Call the Midwife have aired, concluding the sixth series . </P> <Table> <Tr> <Th_colspan="2"> Series </Th> <Th_colspan="2"> Episodes </Th> <Th_colspan="2"> Originally aired </Th> <Th> Ave . UK viewers (millions) </Th> </Tr> <Tr> <Th> First aired </Th> <Th> Last aired </Th> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 6 </Td> <Td_colspan="1"> 15 January 2012 (2012 - 01 - 15) </Td> <Td> 19 February 2012 (2012 - 02 - 19) </Td> <Td> 10.61 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 8 (+ 1) </Td> <Td_colspan="1"> 25 December 2012 (special) 20 January 2013 (2013 - 01 - 20) </Td> <Td> 10 March 2013 (2013 - 03 - 10) </Td> <Td> 10.47 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 8 (+ 1) </Td> <Td_colspan="1"> 25 December 2013 (special) 19 January 2014 (2014 - 01 - 19) </Td> <Td> 9 March 2014 (2014 - 03 - 09) </Td> <Td> 10.54 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 8 (+ 1) </Td> <Td_colspan="1"> 25 December 2014 (special) 18 January 2015 (2015 - 01 - 18) </Td> <Td> 8 March 2015 (2015 - 03 - 08) </Td> <Td> 10.82 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> 5 </Td> <Td_colspan="2"> 8 (+ 1) </Td> <Td_colspan="1"> 25 December 2015 (special) 17 January 2016 (2016 - 01 - 17) </Td> <Td> 6 March 2016 (2016 - 03 - 06) </Td> <Td> 10.54 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> 6 </Td> <Td_colspan="2"> 8 (+ 1) </Td> <Td_colspan="1"> 25 December 2016 (special) 22 January 2017 (2017 - 01 - 22) </Td> <Td> 12 March 2017 (2017 - 03 - 12) </Td> <Td> 10.75 </Td> </Tr> </Table> <Tr> <Th_colspan="2"> Series </Th> <Th_colspan="2"> Episodes </Th> <Th_colspan="2"> Originally aired </Th> <Th> Ave . UK viewers (millions) </Th> </Tr>

Call the midwife season 1 how many episodes