By CHRISTOPHER S. RUGABERWASHINGTON (AP) â¿¿ A survey shows U.S. companies added fewer jobs in March compared with the previous month, as construction firms held off on hiring after three months of solid gains. Private employers added 158,000 jobs last month, payroll processor ADP said Wednesday. That's down from February's gain of 237,000 and January's 177,000. Construction companies didn't add any jobs in March, after average monthly gains of 29,000 in the previous three months. Mark Zandi, chief economist at Moody's Analytics, said the hiring surge during the previous months likely reflected a jump in rebuilding after Superstorm Sandy. Moody's helps compile the monthly report with ADP. The ADP report is derived from actual payroll data and tracks total nonfarm private employment each month. The report suggests that the government's March payroll figures, to be issued Friday, may come in below economists' forecast of 195,000 net jobs. Zandi said the drop job growth last month wasn't significant and that the underlying trend in monthly hiring is roughly 175,000. That's about where it's been for two years. Zandi expects the government's employment report will show hiring at that level in March. "I don't think anything substantively changed in the month of March," he said. Still, there are some signs that the health care reform law may be causing smaller companies to hold off on hiring, Zandi said. That law requires companies with 50 or more full-time workers to provide health insurance to their employees. To make that point, Zandi pointed to mid-sized retailers, hotels, restaurants and service companies â¿¿ all of which slowed hiring last month. Other reports suggest that the job market is improving. The number of people seeking unemployment benefits rose last week but is still lower than in February. That means companies are cutting fewer jobs and may post higher net gains.