Font rendering looks worse in Qt5 for certain font families

Our product makes heavy use of the font family 'Trebuchet MS'.

Attached are screenshots of a dialog with a single centered QLabel with some text set using Trebuchet MS/Normal/18px using the Qt Designer.

Qt 4.8.4 renders the text correctly but in Qt 5.1.1 it looks worse, as if the top and bottom of the text is being clipped.

There doesn't appear to be any workaround other than to try different font sizes.

Regression in Qt 5.