DES MOINES, IOWA (AP) -- Polk County will start enrolling eligible women for a national study on children's health next month.

The National Children's Study is the nation's largest long-term study on children's health. It aims to track 100,000 children from before birth to age 21.

The Polk County Health Department on Wednesday announced enrollment will begin in mid-November. Women ages 18 to 49 at any stage of pregnancy and women who will likely become pregnant are invited to participate.

Polk County is one of 105 locations selected nationwide.

Dr. Jeff Murray of the University of Iowa is a principal investigator with the study. He says there many pediatric diseases with many unknowns, and many are becoming epidemics in children.

(Copyright ©2010 by The Associated Press. All Rights Reserved.)