Hurricanes Katrina and Rita may be responsible for the sharp increase in the risk of stillbirth among pregnant women in the worst hit areas, according to a recent study HealthDay reported.

Researchers from Colorado State University investigated the risk of stillbirth among pregnant women in damaged and undamaged areas in the 28 months after Hurricane Katrina struck.

Katrina struck the state of Louisiana, on Aug. 29, 2005, followed by Hurricane Rita a month later on Sept.24. Katrina was the costliest natural disaster in American history, while Rita was the fourth most intense hurricane ever recorded.

Both hurricanes caused widespread damage to property and infrastructure and left a trail of injury, death, and trauma in their wake.

For the study, researchers used composite figures from several government agencies, showing that the hurricanes caused damage in 38 out of 64 areas (parishes) in the state, with almost 205, 000 housing units affected.

In four parishes, more than half of the local housing stock was damaged; in three others, between 10 percent and 50 percent was damaged. Elsewhere, the level of damage to housing stock was categorized as 1 to 10 percent, or less than 1 percent.

The researchers then calculated the odds of a pregnancy resulting in a stillbirth in damaged and undamaged areas (less than 1 percent damage) in the 20 months before, and the 28 months after, Katrina struck.

They also looked at birth data between 1999 and 2009.

Based on the findings, the risk of a pregnancy ending in a stillbirth was 40 percent higher in parishes where 10 to 50 percent of housing stock had been damaged, and more than twice as high in areas where more than 50 percent of the housing stock had taken a hit.

Researchers determined that every 1 percent increase in the extent of damage to housing stock was associated with a corresponding 7 percent rise in the number of stillbirths.

Based on these figures, the researchers calculated that of the 410 stillbirths officially recorded in extensively damaged parishes, up to half may have been directly caused by the hurricanes and the subsequent devastation.

Their estimates suggest that stillbirths made up around 17.5 to 30.5 percent of the total death toll in the wake of the hurricanes.

Researchers warn that climate change scientists have predicted an increase in the frequency, intensity, and duration of North Atlantic tropical cyclones like Hurricanes Katrina and Rita.

"Insofar as our empirical findings meaningfully generalize in time, the health risks to the unborn and their perinatal development will likely increase with more frequent and intense hurricanes," they write.