Chinese researchers have found that children born to women who were pregnant during the deadliest earthquake of the century have lower intelligence because of trauma suffered by their mothers, an official newspaper reported Friday.

Two doctors at the North China Coal Mine Medical College revealed their findings after testing 350 children born in the northern city of Tangshan, the center of the July 28, 1976, earthquake that killed more than 240,000 people, the China Daily said.Nearly 80 percent of the Tangshan women pregnant at the time of the quake lost family members in the devastation, in which 148,000 of the city's residents died and 81,000 others were seriously injured.

"Grief, tension and worry had an inevitable negative impact on mental development of the fetus regardless of its stage of physical development," the doctors, Li Yurong and Qi Zhenhua, concluded.

They tested 350 schoolchildren in Tangshan, 100 miles east of Beijing, born between the day of the quake and May 30, 1977. The children were divided into two groups - one of 206 whose mothers had experienced the earthquake while pregnant and another of 144 who were born in other regions.

Their findings showed the IQ scores of children from the first group to be lower - by an average of six points - than those of children whose mothers became pregnant with them in other areas.

The doctors attributed the IQ differences to trauma suffered by the mothers of children in the first group, 179 of whom lost relatives in the earthquake, whose main shock measured a massive 7.8 on the Richter scale.

Greater IQ differences were revealed when researchers compared 24 children from each group whose parents came from similar educational and professional backgrounds.