Pregnant women will have to wait for the swine flu vaccine shot due to a Missouri law. The current swine flu vaccine contains a mercury based preservative, thimerosal. Pregnant woman and children three years and younger cannot be vaccinated with anything containing thimerosal under Missouri law.

"The law says we can’t vaccinate pregnant women with thimerosal, so we will wait till we get the new vaccines,” Amanda Powell, Cole County Health Department Vaccinations Coordinator said.

With approximately 60,000 pregnant women in the state, Missouri officials considered them first priority. The nasal spray version of the vaccine, which became available first, is not approved for use in pregnant women because it contains a live virus.

"It’s important that we follow the law and women stay patient. The vaccine is on its way,” Powell said.

The CDC says that thimerosal does not pose a threat to pregnant women and children. Missouri health officials say 11,600 thimerosal-free vaccine shots have been shipped to the state.