Women who are obese before they become pregnant are at higher risk of having children with lower cognitive function - as measured by math and reading tests taken between ages 5 to 7 years - than are mothers with a healthy prepregnancy weight, new research suggests.
In this large observational study, prepregnancy obesity was associated, on average, with a three-point drop in reading scores and a two-point reduction in math scores on a commonly used test of children’s cognitive function.
Previous research has suggested that a woman’s prepregnancy obesity can have a negative effect on fetal organs, such as the heart, liver and pancreas. Because fetal development is rapid and sensitive to a mother’s physiological characteristics, Ohio State University researchers sought to find out whether a mother’s obesity also could affect the fetal brain.
“One way you measure the effects on the brain is by measuring cognition,” said Rika Tanda, lead author of the study and a doctoral candidate in nursing at Ohio State.
The research also supported findings in previous studies suggesting that several other conditions affect childhood cognition, including how stimulating the home environment is, family income and a mother’s education and cognitive skills.
Prepregnancy obesity: a complex risk factor for selected birth defects
Obesity is associated with increased risk of many adverse health conditions. During pregnancy, obesity presents particularly important challenges for both mother and baby. Over the last 20 years, studies have emerged indicating an association between prepregnancy weight and risks of birth defects. However, few studies have examined the mechanisms through which this association occurs. Understanding the underlying mechanisms may provide clues to public health strategies for the prevention of birth defects associated with maternal obesity. This article briefly reviews existing literature on the association between maternal obesity and birth defects, discusses potential underlying mechanisms, and suggests research needed to improve our understanding of this important association.
“The new piece here is we have a measure associated with the fetus’s environment to add to that set of potential risk factors,” said Pamela Salsberry, senior author of the study and a professor of nursing at Ohio State. “If we have a good way to understand the risks each child is born with, we could tailor the post-birth environment in such a way that they could reach their maximum capabilities.”
The research appears online and is scheduled for future print publication in the Maternal and Child Health Journal.
Prepregnancy Obesity as a Risk Factor for Structural Birth Defects
Results Mothers of offspring with spina bifida, heart defects, anorectal atresia, hypospadias, limb reduction defects, diaphragmatic hernia, and omphalocele were significantly more likely to be obese than mothers of controls, with odds ratios ranging between 1.33 and 2.10. Mothers of offspring with gastroschisis were significantly less likely to be obese than mothers of controls.
The reasons for an association between maternal obesity and a spectrum of structural birth defects are unknown. Both animal studies and human studies provide substantial evidence that alterations in glycemic control are responsible for an increased risk of a range of structural birth defects among women who have diabetes prior to becoming pregnant. Thus, a similar mechanism to that occurring in women with diabetes may be responsible for the associations observed between maternal obesity and specific categories of birth defects. Confining our analysis to women without a history of gestational diabetes attenuated many of the ORs but did not substantially explain the general pattern of risk. This may be explained by the fact that it was not possible to exclude those mothers who had undiagnosed or subclinical cases of gestational diabetes or type 2 diabetes. Alternatively, it may point to other reasons for some or all of the associations observed between maternal obesity and birth defects.
В The researchers used data from the National Longitudinal Survey of Youth (NLSY) 1979 Mother and Child Survey, a nationally representative sample of men and women who were 14-21 years old in December 1978. From that dataset, Tanda collected information on 3,412 children born to NLSY mothers who had been full-term births, were between 5 and almost 7 years old at the time of their interview and who had no diagnosed physical or cognition problems.
In addition to documenting a number of characteristics about the mothers and the family environment, the researchers gauged the children’s cognitive function based on their performance on Peabody Individual Achievement Test reading recognition and math assessments.
Prepregnancy obesity and birth defects: what’s next?
Accumulating evidence for adverse outcomes associated with prepregnancy obesity has led several groups to develop guidelines for pregnant women who are obese. Guidelines from the American College of Obstetricians and Gynecologists in 2005 and the Society of Obstetricians and Gynaecologists of Canada in 2010 both emphasize the need for women to be of healthy weight prepregnancy and provide guidance for care of obese women during pregnancy. However, efforts to address the problem of obesity cannot be limited to the clinical care setting. Other sectors, such as communities and worksites, can support individuals in their attempts to follow recommendations for a healthy diet and physical activity. Examples of these environmental and policy supports include increasing the availability and access to affordable, healthy foods; providing access to places for physical activity; and designing streets and neighborhoods to facilitate walking and bicycling.
Obesity is a problem that deleteriously affects the health and health care costs of the population. Concerted efforts across multiple sectors of society to address obesity will benefit the health of the population including that of reproductive-aged women and their children and should serve as one strategy in the prevention of birth defects.
The researchers calculated the mothers’ body mass index (BMI) based on their reported heights and weights. More than half of mothers had normal BMIs before pregnancy, and 9.6 percent were obese, meaning they had a BMI of 30 or higher.