Office vacancies rose a bit in the first quarter, but so did rents. And the region added 272,000 square feet of occupied office space, mostly in the health care sector, according to a report out Wednesday from brokerage Colliers Turley Martin Tucker.

Colliers’ quarterly review of the region’s office market found a vacancy rate overall of 12.1 percent, up from 12 percent in the fourth quarter of 2008 and 11.9 percent a year prior. Empty space rose in Clayton and north and south St. Louis County, while falling a bit in Downtown, Mid-County and St. Charles.

Rents remain highest in Clayton and West County and climbed overall to $18.71 per square foot, up from $18.55 in the fourth quarter.

Overall, the region added 273,000 square feet of tenanted office space, thanks largely to expansions into newly-opened space by Express Scripts in north St. Louis County and BJC Health Care and Missouri College in Brentwood.

But new construction is slow, with just a handful of office projects still underway, and available sublease space jumped. Going forward, Colliers predicted that vacancy would rise and rents fall as more companies cut back and look for deals in response to the weak economy.