Worldwide shipments of tablet computers slowed down in the second quarter because Apple did not release a new model of its iPad, research firm IDC said today.

Shipments totaled 45.1 million units in the three months from April to June, down nearly 10% from the first three months of the year.

But the second-quarter total is up nearly 60% from a year ago, a sign that the market continues to grow.

"A new iPad launch always piques consumer interest in the tablet category and traditionally that has helped both Apple and its competitors," said Tom Mainelli, a research director at IDC. "With no new iPads, the market slowed for many vendors,'' he added.

Apple normally releases a new iPad in the spring, but it has moved toward updating products in the fall to take advantage of the lucrative Christmas shopping season. That means people who want iPads may be holding out for a new model.

Samsung and other rivals have released new tablet models this spring, but IDC said those launches did not get the spillover boost that a new iPad would have provided.

Mainelli said he expects weakness to continue in the third quarter, but tablet shipments should pick up again in the final quarter, when Apple and others are expected to release new products.

Besides a new iPad, is likely to refresh its Kindle Fire line, while Google is expected to come out with a new 10-inch Nexus model. The company released a new 7-inch Nexus last week.

Apple remains the leading maker of tablets, with 14.6 million shipped in the three months from April to June. But as disclosed in the company's earnings report last month, shipments fell 14% from a year ago.

IDC says Apple's market share fell to 32% in the second quarter, compared with 60% in the same period in 2012. Samsung Electronics, maker of the Galaxy line of phones and tablets, saw shipments nearly quadruple to 8.1 million in the second quarter. That gave Samsung a market share of 18%, up from 7.6% a year earlier.

AsusTek Computer, which makes the Nexus 7 for Google along with its own branded tablets, was number three with 2 million tablets. It was followed by Lenovo Group with 1.5 million and Acer with 1.4 million.

Microsoft, maker of the Surface tablets, dropped out of the top five after coming in at number 5 in the first quarter, according to IDC. Amazon also lost its top-five status. It had been number four in the first quarter.