A survey of people hospitalized because of swine flu in California seems to show that obesity is a factor for serious complications. "We were surprised by the frequency of obesity among the severe cases that we've been tracking," said Anne Schuchat, an epidemiologist with Centers for Disease Control and Prevention. Pregnant women in the third trimester are known to be at a higher risk for serious complications from the flu. The fetus and womb compress the lower parts of the lungs during pregnancy, making it harder to breathe deeply and cough forcefully, as well as altering blood flow in the chest. Experts speculate that something similar may be happening in obese people. This has scientists "looking into" the possibility that obese people should be at the head of the line along with other high-risk groups if a swine flu vaccine becomes available. Other high-risk groups include people with diabetes and those suffering from heart disease.