BRUSSELS, Aug 6 - The euro zone economy expanded by 0.1 percent in the first quarter of 2003 from the fourth quarter of 2002, the European Union statistics office said on Wednesday, confirming its previous estimates. Compared with the first quarter of 2002, the euro zone Gross Domestic Product grew by 0.9 percent, a slight upward revision from an 0.8 percent growth estimated by Eurostat on July 10. This was Eurostat's third revision of first quarter growth data. The first estimate from June had shown a stagnation, but this was revised upwards to a 0.1 percent expansion by the second estimate.