Walmart reported its slowest U.S. comparable-sales growth in six years, with sales at stores open at least a year and related online sales rising 2.6% in the second quarter, down from 4.1% in the previous quarter and below FactSet’s 3.8% estimate. Shares fell 6% before Thursday’s opening bell. Excluding wellness, which includes pharmacies, comparable sales increased 3.4%, but federal legislation requiring pharmacies to dispense some high-cost Medicare drugs at capped prices weighed on the category. U.S. e-commerce growth slowed to 24% from 26%. Walmart posted quarterly net income of $6.37 billion, or 80 cents per share, adjusted earnings of 81 cents per share, and sales of $187.94 billion, beating analysts’ estimates. Its third-quarter and full-year forecasts were below consensus, reflecting caution as retailers assess consumer demand amid higher costs for gas, groceries and other goods.