Brock prof: Link between smoking moms, infant obesity
Smoking during pregnancy puts children at a higher risk for obesity.
A joint study between researchers at Brock University and the State University of New York at Buffalo found that babies exposed to cigarette smoke in the womb were gaining weight faster than they should have by the time they were two years old, said Danielle Molnar, assistant professor in Brock’s Department of Child and Youth Studies.
And that increases their chances of being obese later in life, she said.
The researchers followed 174 women – 117 smokers and 57 nonsmokers – from their first prenatal visit. The women were all young, and from a low-income population. Researchers took into account other factors including the mother’s health, her weight gain during pregnancy, and made sure they were not using drugs or alcohol in order to zero in on the effect of nicotine.
On average, the women smoked about five cigarettes a day. Some more. Some less.
The study found that smoking during the second and third trimester of pregnancy had the biggest impact and that the more cigarettes a pregnant women smoked, the more rapidly their children gained weight by age two.
“But even low levels of smoking is associated with increased levels of obesity risk,” said Molnar, the study’s co-investigator.
Along with Rina Eiden, senior research scientist and the study’s principle investigator at the Research Institute on Addictions, they hope to follow the children into adulthood. Their children are now in kindergarten to Grade 3.
Health risks of obesity include poor heart health, diabetes and an increased risk for some cancers, said Molnar.
Soon after the babies were born, their first stool was analyzed. The stool – called meconium – can show how much nicotine they were exposed to during the third trimester, she said.
It’s long been known that smoking during pregnancy can cause premature babies, low birth weight and babies born with a smaller head circumference.
But the question was, can it affect children’s weight gain later on in life?
Other studies have shown a connection to smoking and obesity, but they have largely relied on the mother’s memory of smoking habits during pregnancy. This is the first study to have followed women from early pregnancy, said Molnar.
When a woman smokes during pregnancy, blood flow to the baby is restricted. That means that less oxygen and nutrients are delivered to the developing fetus.
It’s thought that the fetus adapts to this shortage, by becoming more efficient at using and storing what little nutrients come its way. When it’s born, the baby continues to operate this way, as if it’s been programmed to expect a deficiency, even when it gets ample, or even an over abundance of food, she said.
And that results in weight gain that’s faster than it should be for the child’s height, she said.
Researchers will also look at the child’s environment after birth, and determine the extent that factors like nutrition and secondhand smoke exposure affect weight gain, she said. And whether or not the baby’s in-the-womb programming can be overcome in childhood.
She hopes the study sends an important message to doctors, women and to anyone who is supporting them during pregnancy.
Doctors traditionally discuss smoking with women when they first become pregnant. But the study has shown that smoking has the biggest impact during the last two trimesters, so physicians need to revisit the topic throughout a woman’s pregnancy, said Molnar.
And women need to know that it’s not all or nothing.
“Obviously, abstinence is best,” she said.
“But even if women reduce smoking, that still will have a beneficial effect for their child.”