Hurricane Katrina created a unique opportunity to study a large population of pregnant women who experienced the same stressful event, says Pathik Wadhwa, a behavioral medicine researcher at the University of California at Irvine, who studies how maternal stress affects an unborn baby's health.

The results could help scientists understand the short- and long-term effects of maternal stress, as well as the stages of pregnancy when stress is most harmful. Previous research in humans has shown that extreme maternal stress is linked to premature birth and babies with low birth weight. Animal studies also suggest that stress has wide-ranging impacts on processes such as the development of the immune system and the brain.

Wadhwa and his colleagues are working with the US Federal Emergency Management Agency to compile a registry of pregnant women who survived the disaster in order to track their health over time. They plan to assess the level of stress that these women experienced during the disaster, such as if they lost their homes or were evacuated, and to evaluate their babies' health and complications during pregnancy and birth. Because women were in different stages of pregnancy when the hurricane struck, researchers can try to determine which periods of fetal development are most vulnerable to stress.

Much of the data can be collected later in time, which eases ethical concerns about asking women who are still recovering from the disaster to participate in a study, says Wadhwa. For example, researchers can use medical records compiled during birth to assess pregnancy complications and infant health.

Researchers are still working out details of the study, but they ultimately hope to follow some children for several years. They might also take DNA samples to assess how gene-environment interactions affect the impact of stress.