The launch of Obamacare in October has shaken up American health care in a big way. From the expansion of Medicaid to cuts to Medicare and insurers playing cautious with state health-care exchanges, the past few months have seen a major transformation of this sector -- and there's no industry feeling the effects of Obamacare like the health insurance industry.

UnitedHealth Group (NYSE:UNH), America's largest publicly traded insurer, announced earlier this week that the rollout of Obamacare in 2014 could end up costing the insurer up to $1 in full-year net earnings per share. Ouch! That's a hefty blow to UnitedHealth's forecast, and it's cuts to Medicare that have taken an especially big bite out of that downbeat outlook.

But what can UnitedHealth's look ahead tell investors about how Obamacare will impact this industry's biggest stocks? Find out in the video below, where Motley Fool contributor Dan Carroll explains how some of health insurance's biggest names, from WellPoint(NYSE:ANTM) to Humana (NYSE:HUM), could see major impacts from the new health-care law's changes to Americans' coverage.

Fool contributor Dan Carroll has no position in any stocks mentioned. The Motley Fool recommends UnitedHealth Group and WellPoint and owns shares of WellPoint. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.