Mother's hypertension during pregnancy may affect child's IQ later in life

Mothers with high blood pressure during pregnancy may put their babies at an increased risk for a lower IQ later in life, a new study suggests.

The researched stemmed from extensive previous evidence, which has linked low birth weight in newborns with an increased risk of aging-related disorders and lower cognitive function. Researchers from the University of Helsinki in Finland were hoping to uncover some of the mechanisms involved in this established link.

“Lower birth rate is a proxy of environmental factors during pregnancy,” study author Katri Räikkönen, a researcher at the University of Helsinki, told  “And preeclampsia, or high blood pressure, is one of those environmental factors.”

Räikkönen and her colleagues analyzed medical records from 398 Finnish mothers and their sons.  The sons were born between 1934 and 1944 and followed into adulthood.

Each man involved in the study was given two cognitive tests, which tested language skills, math, and spatial relationships.  One test was administered at the age of 20 and another around the age of 68.  Cross examining their results with their mothers’ blood pressure, the results showed men whose mothers had high blood pressure while pregnant scored 4.36 points lower on the cognitive test in older age than those whose mothers had normal blood pressure.

“Not only did they score lower, but their decline in cognition was greater – so they lose cognitive function more quickly,” Räikkönen said.  “One of the exceptional things is that we were able to measure cognitive ability at both 20 and 68 years of age, using the same cognitive measurement device.  So we were able to test their cognitive ability before any decline could be expected to occur.”

However, Räikkönen cautioned that the results could be somewhat skewed, because the measurements for high blood pressure have evolved significantly over time.

“The data are limited by the measurement limitations used in 1934,” Räikkönen said.  “Medicine hadn’t developed to the state it has now.  The hypertension spectrum disorder criteria that were used in this study do not compare to the hypertension criteria we use now.”

The researchers also noted that while there is an association, the results do not necessarily prove that blood pressure in pregnancy causes lower IQ.  Most importantly, Räikkönen said that the results need to be replicated in order to confirm the link to be clinically significant.  In the meantime, she said the results reiterate how mothers need to take care of their bodies while they’re pregnant.

“Mothers should look after not just their physical health but also their psychological health,” Räikkönen said.  “Stress is well known to have cardiovascular consequences of heightening blood pressure.  If these factors are persistent, then the blood pressure may consistently be more reactive and more elevated.”

For mothers who suffer from pregnancy disorders such as preeclampsia and are worried about their newborn, there are many protective measures they can take to better ensure that their children live a healthy life.

“More attention should be paid to the development of the offspring,” Räikkönen said.  “Some factors during post-natal life can be protective like breast feeding and good quality parenting.  These habits can override the adversities a mother doesn’t have control over during pregnancy.”

The study was published in the Oct. 3 online issue of Neurology, the medical journal of the American Academy of Neurology.