Aetna (AET), which is holding its investor day, joins United Health and Cigna in providing 2013 guidance that's below consensus. Aetna forecasts EPS of at least $5.40 vs consensus of $5.52 and revenue growth of 9% to $38.6B vs $38.91B. Predicts that commercial-medical costs will rise 6.5%, the same as this year. BMO analyst Dave Shove says the outlook reflects "management’s cautious stance on guiding high." Shares +4.2%.