Adds background April 25 (Reuters) - United Parcel Service Inc UPS.N on Tuesday reported a fall in first-quarter profit, as the freight bellwether grappled with softening e-commerce demand due to economic uncertainties. The global shipping downturn has squeezed margins for most operators in the sector as the COVID-19 pandemic-driven e-commerce bubble deflates and shoppers wrestle with soaring inflation. On Tuesday, the company posted an adjusted profit of $2.20 per share for the quarter through March, compared with $3.05 a year earlier.