A starring role from captain and fullback Niamh Briggs was key, as was Ireland’s all round patience as they held Wales out with a clinical attacking show and excellent defence, helped by the outstanding play of flanker Claire Molloy.
The victory means Ireland are level on six points with defending champions France at the top of the table but the French have a better points difference of +63 compared to Ireland's +43.
If France win against England at Twickenham next weekend, Ireland will hope to rack up a big score against Scotland in order to pip them to the title. A final win of any kind would give the Irish their second Triple Crown in three years. A French loss means Ireland would just need any kind of win or draw to secure their second title.
Ireland started the game well with carries from Sophie Spence and Briggs as they started to take the game to Wales in attack.
Briggs released Allison Miller for a powerful run from deep and scrum half Larissa Muldoon, playing against some of her Skewen club-mates, caught the eye in both attack and defence.
Gemma Rowland was pinged for not rolling away and the Irish pack chipped away following an initial lineout maul, showing impressive composure and patience through a series of pick and goes before flanker Paula Fitzpatrick reached over to score by the left hand post. Briggs comfortably converted, but Wales enjoyed an encouraging finish to the first half with dangerous winger Laurie Harries getting into the game and their pack pressing from a couple of penalties just five metres out.
However, Ireland, with hooker Gillian Bourke winning her 50th cap, were unyielding. The excellent Claire Molloy produced a vital turnover at a ruck and Briggs, having made some uncharacteristic errors, redeemed herself with a penalty-winning poach in the dying minutes.
Ireland responded to a bright Welsh start on the resumption with a drilled Briggs kick downfield and perfect follow-up tackle from Tyrrell, before tighthead Ailis Egan rampaged forward from a free-kick in the 22.
Another ruck penalty won by Molloy saw Briggs go for goal from the left, just outside the 22, and her accurate strike widened the margin to 10 points. Further pressure from a lengthy Briggs kick saw Dyddgu Hywel charged down by Tyrrell who was unfortunate that the loose ball beat her over the end-line.
Briggs increased her influence with the boot and also with ball in hand, countering brilliantly from a Welsh chip as she weaved her way up towards the 22. The Waterford woman then curled a pinpoint penalty inside the right hand post for 13-0.
There were errors from both sides in an absorbing final quarter as the young Welsh side continued to knock on the door, aided by two outstanding breaks from captain Rachel Taylor and the elusive Elen Evans.
Then, in the final minutes, Miller made her own luck when she gobbled up an Elinor Snowsill cross-field kick, charged over halfway and made it over in the left corner. Briggs' fine conversion from wide out completed the scoring at St. Helen's.
Wales: Dyddgu Hywel (Pontyclun/Scarlets); Laurie Harries (Llandaff North/Blues), Adi Taviner (Skewen/Ospreys), Gemma Rowland (Wasps/Dragons), Elen Evans (Waterloo/Scarlets); Elinor Snowsill (Dragons), Amy Day (Llandaff North/Dragons); Jenny Davies (Caernarfon/Blues), Carys Phillips (Bath/Scarlets), Catrin Edwards (Llandaff North/Scarlets), Jenny Hawkins (Llandaff North/Blues), Rachel Taylor (Bristol/Dragons) (capt), Sian Williams (Worcester/Dragons), Sioned Harries (Whitland/Scarlets), Shona Powell Hughes (Skewen/Ospreys).
Replacements used: Kerin Lake (Skewen/Ospreys) for Hywel, Caryl Thomas (Bath/Scarlets for Davies (both 52 mins), Amy Evans (Skewen/Ospreys) for Edwards (60), Amy Lawrence (Skewen/Ospreys) for Phillips, Rebecca Rowe (London Welsh/Dragons) for Hawkins (both 77), Hannah Jones (Pennybanc/Scarlets) for Snowsill, Keira Bevan (Skewen/Ospreys) for Day, Melissa Clay (Pencoed/Ospreys) for Williams (all 80).
Ireland: Niamh Briggs (UL Bohemians/Munster) (capt); Hannah Tyrrell (Old Belvedere/Leinster), Jenny Murphy (Old Belvedere/Leinster), Jackie Shiels (Richmond/Exile), Alison Miller (Portlaoise/Connacht); Nora Stapleton (Old Belvedere/Leinster), Larissa Muldoon (Skewen); Ruth O'Reilly (Galwegians/Connacht), Gillian Bourke (Olympico de Pozuelo), Ailis Egan (Old Belvedere/Leinster), Sophie Spence (Old Belvedere/Leinster), Marie Louise Reilly (Old Belvedere/Leinster), Paula Fitzpatrick (St. Mary's/Leinster), Claire Molloy (Bristol/Connacht), Heather O'Brien (Highfield/Munster).
Replacements used: Sene Naoupu (Galwegians/Connacht) for Shiels (20-26 mins, temp sub), Orla Fitzsimons (St. Mary's/Leinster) for O'Brien (34), Fiona Hayes (UL Bohemians/Munster) for O'Reilly, Tania Rosser (Blackrock/Leinster) for Muldoon (both 55), Naoupu for Stapleton (68), Sarah Mimnagh (Wasps/Exile) for Bourke, Fiona O'Brien (Old Belvedere/Leinster) for Egan, Katie Norris (Blackrock/Leinster) for Spence, Aoife Doyle (Shannon/Munster) for Tyrrell (all 80).