High blood pressure during pregnancy may hurt offspring’s IQ

The children of mothers who have hypertension during pregnancy score lower on IQ tests 20 and 68 years after birth, according to a new study. The report, published Wednesday in the journal Neurology, is the first to draw a connection between high blood pressure during pregnancy and adult intelligence.

Hypertension during pregnancy has been linked to premature birth and small body size, which in turn have been connected to deficits in cognitive abilities. But hypertension itself had yet to be connected directly to intelligence, a gap this study attempts to fill in.

The research, conducted in Finland, used data collected as part of a survey called the Helsinki Birth Cohort. It tracked Finns born between 1934 and 1944 and included data about their moms’ blood pressure during pregnancy. They matched that with data from 398 men who received an intelligence test when they entered compulsory military service at age 20. Those same men were retested around their late 60s.

Overall, the men born to hypertensive mothers did worse on the intelligence test. But the test had three sections -- verbal, spatial, and arithmetic intelligence -- and each area was affected differently. Arithmetic intelligence was the most negatively affected, verbal memory was mildly affected, and spatial memory appeared to be unaffected. The researchers are unsure why the three types of intelligence seem to be affected in different ways.

The researchers did their best to control for important confounding factors such as socioeconomic status, birth weight and the age of the mother at birth. But because the data are old, it is difficult to be sure the effect is truly a result of high blood pressure as opposed to a factor not included in the study. Another shortcoming: The study only included men, since they were the only ones required to enter the military.

Though the study provides little mechanistic insight into why hypertension during pregnancy might dampen the intelligence of one’s son, the authors note that a large percentage of brain development occurs prenatally. As a result, a health condition like hypertension that might impact the flow of blood or nutrition to the fetus could disrupt such development, the authors wrote--a hypothesis that will need to be tested in follow-up studies.

You can read a summary of the study here.

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