After two minutes, flying Welsh winger Haley Baxter rounded the defence and outsprinted the Irish cover to score from almost halfway. Stacey Saunders converted to give the Welsh a 7-0 lead and left the Irish stunned.
Midway through the half, Baxter pounced on a poor pass and ran in untouched from 65m. Saunders added the extra points from in front of the posts for a 14-0 interval lead. Ireland stormed back after the break and narrowed the gap after 10 minutes when Joy Neville fed Fiona Steed for a try. The difficult conversion was missed by Sarah Jane Belton, but there was a glimmer of hope for Ireland at 14-5.
Steed was to be the hero again, when diving over after a powerful Irish rolling maul stopped short of the Welsh line.
Belton missed the conversion but made amends with a penalty minutes later to cut the deficit to a point.
Ireland had three chances to snatch victory in the final five minutes but could not breach the Welsh defence.
Ireland play England at Twickenham in two weeks' time.
S Belton, N Milne, S Fleming, P Kelly, L Cantwell, J O'Sullivan, L Beamish, F Coghlan, J Lonergan, G McAlliste, R Foley, A Marie McAllister, R Boyd, F Steed (vc), Y Neville. Subs: N Ní Chadhain for N. Milne, M Dolofor G. McAllister.