Shares of Molina Healthcare Inc. plummeted last week after a first-quarter earnings miss.

The Long Beach managed care provider saw its stock price fall 29 percent to close at $46.23 for the week ended May 4, making it the biggest loser on the LABJ’s Stock Index. (See page 28.) The drop was largely attributed to decreased earnings of 43 cents a share for the first quarter ended March 31, compared with 56 cents a share for the same period a year ago. The company reported a net income of $24 million in the first quarter compared with $28 million a year ago – a decrease of 14 percent. The income dip came in spite of a 34 percent year-over-year gain in premium revenue, to $4 billion from $2.97 billion, thanks to surging enrollment.

Chief Executive J. Mario Molina acknowledged in a conference call that results were not in line with expectations.

“We have identified those factors that affected our results. We are working diligently to address them,” he said, adding that Medicaid reimbursement rates had failed to keep up with rising medical costs, which also contributed to lower earnings.

Analysts pointed to a flurry of acquisitions by Molina as also playing a role.

In recent quarters, the company acquired two mental health subsidiaries of Tucson, Ariz.’s Providence Service Corp. for approximately $200 million, along with Medicaid businesses in Florida, Michigan, and Illinois.

“Managing rapid growth is difficult,” said Peter Costa, a senior analyst at Wells Fargo in Boston.

Matthew Borsch, a health care analyst at Goldman Sachs in New York, said in a research note that Molina could potentially be acquired by one of the larger managed care companies, noting a steady trend toward consolidation within the health care sector. Due to the risk of another earnings shortfall in the second quarter, Goldman Sachs downgraded its recommendation on the stock from “neutral” to “sell.”