Hypertension in pregnancy has already been linked to low birth weight and early delivery. Now it appears it can also lower a baby\'s IQ and later boost cognitive decline.

Hypertension in pregnancy has already been linked to low birth weight and premature birth. Now it appears that mom's high blood pressure can also lower a baby's IQ, as well as boost cognitive decline years later, a new study says.

"Hyptertensive disorders in pregnancy predict lower cognitive ability and greater cognitive decline over decades in the adult offspring," Finnish researchers wrote in a study just published in the journal Neurology.

About 8 percent of pregnant women have high blood pressure. And while the National Institutes of Health says that most of them will have uneventful pregnancies, there are potential fetal complications.

"It's a fairly serious problem and one we often have to manage in the field of high-risk obstetrics," Dr. David Hackney of UH Case Medical Center in Cleveland, Ohio, told ABC News. "If a woman develops preeclampsia, the treatment is to deliver the baby. But obviously you don't want to do that if it's too early."

The article by Katie Moisse noted that other studies have found that prematurity and low birth weight are often accompanied by lower IQ in adulthood. "The new study suggests high blood pressure may be the early instigator," she wrote.

The researchers said that during pregnancy the baby's brain and function develops and it is at that time that future brain power is formed. That's why it is important to manage health before and during pregnancy.

"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," study author Katri Räikkönen, from the University of Helsinki, Finland, told the BBC. "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."

The NIH suggests that before becoming pregnant, women should change lifestyle habits to limit salt intake, get exercise and lose weight, if needed. Certain medications for managing blood pressure may not be safe during pregnancy, so it's important to talk to the doctor. Once someone is pregnant, she should stop using alcohol or tobacco, get adequate prenatal care and ask about the safety of any over-the-counter medications she uses, the government agency said.

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The research itself involved men in Finland who between 1934 and 1944 were born to women who had their blood pressure recorded during their pregnancies. The sons of those who had high blood pressure scored lower on tests taken as part of compulsory military service at age 20. And when they were retested at age 69, they scored an average of 4.36 points lower on thinking ability tests. Their scores also declined faster over the years than those of their peers.

The test used was the Finnish Defence Force test, a multiple-choice exam with sections of language, math and spatial reasoning. Math-related scores were most affected. The researchers noted that when they looked at whether premature birth played a role in the finding for those men, they found no link. And what kind of career or job the men ultimately had didn't change the results, either.

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