Spot gold fell 0.2 percent to $1,171.16 an ounce by 2:38 p.m EDT.
U.S. gold futures for February delivery settled to $1,172.40 an ounce.
Bullion has shed more than 12 percent since its post-U.S. election peak of $1,337.40 on Nov. 9.
"If the ECB has the ability to trigger euro-dollar weakness again, and it breaks under the key 104.58-105 level, then you'll get the next phase of a dollar rally, which will be painful for gold," said Georgette Boele, ABN AMRO commodity strategist in Amsterdam.
The euro gave up all its gains versus the dollar after the ECB move, falling more than 1 percent to a low of 106.22.
Also weighing on gold were increased expectations the U.S. Federal Reserve will increase interest rates at its policy meeting next week, as higher U.S. rates raise the opportunity cost of holding non-yielding bullion.
Interest rates futures implied traders saw a 97 percent chance the Fed would raise rates at its policy meeting (FOMC) next Tuesday and Wednesday, CME Group's FedWatch program showed.
"As we head into the FOMC, it is certain that the Fed will raise rates this time. I believe this is mostly priced into gold. We might still see some reaction and the recent low of $1,157 may be revisited again," said Brian Lan, managing director at Singapore-based gold dealer GoldSilver Central.
Gold may get support, however, after the Fed meeting if investors close out positions betting price on falls, but this would only be temporary reprieve before a fresh bout of gold weakness in the New Year, Boele said.
Holdings of SPDR Gold Trust, the world's largest gold-backed exchange-traded fund (ETF), dropped 0.72 percent to 863.67 tonnes on Wednesday from a day earlier. Holdings have fallen more than 8 percent since November.