By David Morgan and Deborah Zabarenko WASHINGTON (Reuters) - The top Democrat in the U.S. House of Representatives said on Sunday that her party would not retreat from President Barack Obama's landmark healthcare reform law, despite unrelenting Republican opposition and emerging signs of market turmoil for consumers and health insurers. Two days after 39 House Democrats joined Republicans on a bill aimed at undermining the law known as Obamacare, House Democratic leader Nancy Pelosi denied that Democrats have lost confidence in Obama's ability to overcome a botched rollout of his signature domestic policy achievement. "There's a lot of whoop-de-do and ado about what's happening," Pelosi told NBC's "Meet the Press" program. No. It's too valuable for the American people," she said, claiming similar numbers of Democratic lawmakers have joined Republicans on votes that challenged Obamacare in the past.