IOWA CITY — The University of Iowa Stead Family Children’s Hospital has been up and running for more than a year, but the $360 million, 14-floor facility has not yet improved the pediatric hospital’s national rankings as expected.A U.S. News & World Report ranking of top pediatric specialties released Tuesday places the Children’s Hospital among the nation’s 50 best in four areas — but that’s down from its top ranking in six specialties last year, eight in 2016 and nine in 2015.And all but one of UI’s four ranked pediatric specialties lost ground this time, according to the “2018-19 Best Children’s Hospitals” report.Its pediatric cancer ranking, which dropped from 27 to 34 last year, decreased further to 36 in the new rankings.Its neonatology ranking, which improved last year from 28 to 20, this year just eked into the top 50 at 49.The pediatric nephrology ranking slipped to 28 from 21 last year.