On a quiet day on the news front, the stock market took the path of least resistance and dropped modestly. Although the latest reading on consumer confidence soared well beyond expectations and home prices posted a 9.3% year-over-year gain, a disappointing measure of manufacturing activity in the Chicago region led investors to take a break from the run that has lifted the Dow Jones Industrials (DJINDICES:^DJI) by between 1% and 2% for the month of April so far. As of 10:50 a.m. EDT, the Dow is down 30 points, or 0.2%, while the broader market posted somewhat smaller losses on a percentage basis.

Weakness in the Dow centered on the health care sector. Pfizer (NYSE:PFE) fell 3.3% after it cut its earnings guidance for the full 2013 year by $0.06 per share. The drugmaker now expects profit to come in between $2.14 and $2.24 per share. Given that and disappointing results showing that sales fell 9% and net income fell $0.01 per share short of expectations, Pfizer needs to demonstrate its ability to sell its stable of approved drugs. Otherwise, continued pressure from generic competition will continue to weigh on revenue well into the future.

UnitedHealth (NYSE:UNH) also fell, losing 0.9% on the same day that rival Aetna (NYSE:AET) reported earnings. Aetna managed to increase its earnings by keeping premium prices high and cutting its costs, and it's positioning itself to deal with the onset of health exchanges and other key provisions of Obamacare that will take effect within the next year. But what's increasingly clear is that competition among health insurance carriers will become fierce as Obamacare is increasingly implemented, and UnitedHealth needs to defend its leadership position by getting its plans onto as many health exchanges as possible without cutting profit margins any further than the new health-care law will require.

Finally, outside the Dow, Best Buy (NYSE:BBY) has soared almost 11% after selling its stake in its Best Buy Europe joint venture to its partner for $775 million. Under the deal, Carphone Warehouse Group will take over the venture, which originally had grand plans for expansion but foundered due to the weak European economy and Best Buy's own troubles. The move should help Best Buy focus more on its restructuring efforts in the U.S. and in other international markets.

Fool contributor Dan Caplinger has no position in any stocks mentioned. You can follow him on Twitter @DanCaplinger. The Motley Fool recommends UnitedHealth Group. Try any of our Foolish newsletter services free for 30 days. We Fools may not 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.