A bill making its way through Congress to provide more low-income children with health-insurance coverage could spell financial trouble for scores of hospitals owned by physicians. The proposed legislation will prohibit "the unethical kickbacks that physicians receive from ownership hospitals, most of which are of questionable safety and quality," said Rep. Pete Stark, chairman of the House Ways and Means health subcommittee. A provision that Rep. Stark helped write in the child-health bill would effectively put a halt to the construction of any new doctor-owned hospitals and would seriously hamper plans of existing ones to expand.