A new study suggests that mothers with high blood pressure during pregnancy might have a detrimental effect on their child’s IQ. The research was published this week in the American Academy of Neurology’s medical journal, Neurology.

The study found that men whose mother’s blood pressure was high during pregnancy scored 4.36 points lower on “thinking ability tests” at age 69 than men whose mother’s did not have high blood pressure. Researchers also found that these men scored lower than others at age 20 and had greater declines in their scores over time. This trend was seen most noticeably for math reasoning skills.

“High blood pressure and related conditions such as preeclampsia complicate about 10 percent of all pregnancies and can affect a baby’s environment in the womb,” said Dr. Katri Räikönen, lead author of the study and professor of psychology at the University of Helsinki. “Our study suggests that even declines in thinking abilities in old age could have originated during the prenatal period when the majority of the development of brain structure and function occurs.”

The study looked at the medical records of mothers with high blood pressure during pregnancy for 398 men born between 1934 and 1944. The men were tested on their thinking abilities at age 20 and age 69. The tests included measurements of language skills, math reasoning, and visual and spatial relationships.

Researchers isolated other factors and found that premature birth did not affect the men’s thinking abilities. Likewise, whether a man’s father was a blue-collar or white-collar worker made no difference in his child’s thinking abilities.