Fascinating! According to Wikipedia (take it for what it's worth):
"The poem is also connected to the 1918–1919 flu pandemic: In the weeks preceding Yeats's writing of the poem, his pregnant wife Georgie Hyde-Lees caught the virus and was very close to death. The highest death rates of the pandemic were among pregnant women—in some areas, they had up to a 70 percent death rate. While his wife was convalescing, he wrote "The Second Coming"."
