Private U.S. companies added jobs at a slightly slower-than-expected pace in August, with gains concentrated heavily in healthcare and a few other industries, ADP reported Wednesday.

The payrolls processing firm said firms added 38,000 workers, fewer than the upwardly revised 46,000 in July and below the Dow Jones consensus estimate for 47,000.

Though job creation held positive, August was the smallest gain since January and reflective of a broader slowdown in the labor market. Moreover, most of the jobs came from three sectors, with multiple others showing declines.

Education and health services added 45,000 to lead all categories, with the latter group being at the forefront of employment growth.

Leisure and hospitality added 16,000 positions and construction was up 12,000. Outside of that, though, there were few growth areas.

Manufacturing lost 17,000 jobs, professional and business services was off 16,000, and both natural resources and mining as well as trade, transportation and utilities reported declines of 5,000.

Almost all of the gains came from big business, with companies employing 500 or more workers adding 34,000 while those with fewer than 50 employees rose by 3,000.

ADP's numbers also showed that pay gains held steady for the month. The firm added a feature in August in which it broke down growth between base and gross pay, the latter including tips, commissions, bonuses and other earnings.

For those staying in their jobs, base pay rose 3% from a year ago while gross pay increased 4.4%, both unchanged from July. For all workers, the respective increases were 3.2% and 4.7%.

The ADP report serves as a precursor to the Bureau of Labor Statistics' nonfarm payrolls release, due out Friday, which is expected to show an increase of 53,000, after the 23,000 decline in July. The unemployment rate is forecast to hold at 4.1%.