A toxic chemical known as C8 may cause birth defects and other health problems in pregnant women, a scientific panel said in documents made public Thursday. According to reports released by the three-member committee from the Mount Sinai School of Medicine, initial analysis showed that mothers with high levels of C8 were 70 percent more likely to have children with birth defects and 30 percent more likely to suffer from high blood pressure during pregnancy. The findings come as part of a multimillion dollar settlement over contamination from a DuPont plant in West Virginia.