U.S. stocks fluctuated sharply as President Trump is set to unveil significant tariffs during a highly-anticipated announcement. While the S&P 500 rose 0.4% before the news, global markets have struggled, with the MSCI World Index indicating March was the worst month in 18 months, particularly impacting European stocks, which fell by 4.18%. Investors fear the tariffs, which could affect the pharmaceutical sector, may suppress U.S. economic growth and exacerbate inflation. Analysts anticipate continued uncertainty post-announcement, with concerns over retaliatory measures and the potential for a prolonged negative market impact.