WASHINGTON, Aug 18 (Reuters) - An average middle-income family in the United States can expect to spend about $245,000 over 18 years to raise a child born in 2013, the U.S. government estimated on Monday.The Department of Agriculture???s annual ???Cost of Raising a Child??? report showed child-rearing costs - which reflect food, housing, childcare, education and other expenses - were up about 1.8