that should work. i just tried a test of:
<?php
$row_newsRS['newsContent'] = "<p>This is one</p><p>This is two</p><p>This is three</p>";
$str = "<p>This is one</p><p>This is two</p><p>This is three</p>";
$pattern="/(<p[^>]*>(.*)<\/p>){2}/isU";
preg_match($pattern,$str,$matches);
echo htmlentities($matches[0]);
?>
and got the desired result.