get_comments() where parent is not 0

I need a way to get just the comments that aren’t top level i.e. where parent is not 0.

I’ve tried:

$args = array(
   'parent' => -0
);
$comments = get_comments($args);

I know the parent comment id’s (44 and 48) of all the comments I require, so I tried:

$args = array(
   'parent' => array(44,48)
);

$comments = get_comments($args);

But this didn’t work. It only returned one row.
I need to stick with get_comments() if possible, as I’ve done a lot of work around it already so want to avoid losing what I’ve done.

You cannot do that with a parameter for get_comments(), but filtering 'comments_clauses' should do it.

Sample code, not tested:

add_filter( 'comments_clauses', 'wpse_78490_child_comments_only' );

function wpse_78490_child_comments_only( $clauses )
{
    $clauses['where'] .= ' AND comment_parent != 0';
    return $clauses;
}