November 3rd, 2009 
New research set to be published in the Journal of Epidemiology and Community Health suggests that mothers who smoke while pregnant are essentially toying with the brain chemistry of their future children.
“There are 4000 toxic substances in cigarette smoke, and many of these will pass into the brain of the fetus, and it is possible that they could have an effect on how the brain chemistry works,” said Professor Alan Maryon-Davis, president of the Faculty of Public Health, to the BBC.
The research involved more than 14,000 pairs of mothers and their children, all participants in the Millennium Cohort Study, a study that focused on children born in the U.K. between 2000 and 2001.
First, mothers were put into categories based upon the amount of cigarettes they smoked during pregnancy. Then, using a validated questionnaire called Strengths and Difficulties, mothers were asked to grade their children’s level of hyperactivity, type of temperament, frequency of fights, and ease of distraction. Taking into account factors that might influence the results, including socioeconomic status, mother’s age, and level of education, the researchers began analyzing the data.
It was found that nearly one in ten women smoked heavily during pregnancy, 12.5 percent smoked lightly during pregnancy, and 12.4 percent said they stopped smoking while pregnant.
Boys of mothers who smoked heavily while pregnant were almost twice as likely to have behavioral problems, while boys of mothers who smoked lightly while pregnant had an 80 percent increased likelihood of having an attention deficit disorder.
Researchers found a significant increase in likelihood that those girls of mothers who smoked lightly or heavily had conduct issues.
“Smoking during pregnancy may damage the developing structure and function of the fetal brain, which has already been shown to be the case in animals”, said the authors.
“The fetal development of boys may also be more sensitive to this kind of chemical assault, which might explain why boys are more likely to have behavioral problems than girls.”
Related
- Smoking in pregnancy risks psychotic children
Mothers who smoke during pregnancy put their children at greater risk of developing psychotic symptoms as teenagers, British scientists said on Thursday.
Researchers from four British universities studied 6,356 12-year-olds and interviewed them for psychotic-like symptoms such as hallucinations or delusions. Around 19 percent had mothers who smoked during pregnancy.
Just over 11 percent, or 734 of the total group, had suspected or definite symptoms of psychosis.
Many previous studies have shown cigarettes can harm the fetuses of mothers who smoke while pregnant. The risks include causing babies to be born smaller and increasing the risk of sudden infant death syndrome or heart defects.
Stanley Zammit, a psychiatrist at Cardiff University’s School of Medicine who led the study, said the more the mothers smoked, the more likely their children were to have psychotic symptoms.
“We can estimate that about 20 percent of adolescents in this cohort would not have developed psychotic symptoms if their mothers had not smoked,” he said.
Despite countless studies flagging up the risks to babies, it is estimated that between 15 and 20 percent of women in Britain smoke during pregnancy.
The researchers also found drinking during pregnancy was associated with increased psychotic symptoms, but only in children whose mothers had drunk more than 21 units of alcohol a week in early pregnancy.
The reasons for the link between maternal smoking and psychotic symptoms are not clear, but Zammit and colleagues suggested that exposure to tobacco in the womb might affect a child’s impulsivity, attention or cognition.
Only a few mothers in the study, which was published in the British Journal of Psychiatry, said they had smoked cannabis during pregnancy, and this was not found to have any significant link with psychotic symptoms.
- Smoking During Pregnancy Linked to Drug Use in Teenagers
Teenagers whose mothers smoked during pregnancy are more likely to experiment with drugs, according to a new study.
The research, carried out by scientists at the University of Nottingham, found children exposed to cigarette smoke in the womb were more likely to experiment with alcohol, tobacco and cannabis.
This is because prenatal exposure to maternal smoking may affect the development of the orbitofrontal cortex, a part the brain which evaluates rewards and regulates emotion.
Academics analysed MRI scans from almost 400 teenagers and found that those born to mothers who smoked during pregnancy had a thinner orbitofrontal cortex.
Scientists then found those suffering from a thinning of this part of the brain were more likely to experiment with a wider range of drugs.
The most commonly used illegal substances among the participants in the study were alcohol, tobacco, cannabis, stimulants and psychedelic drugs.
Professor Tomas Paus, senior author of the study at the University of Nottingham, said: “These findings demonstrate significant consequences of prenatal exposure to maternal cigarette smoking on a child’s brain.
“But our findings need to be interpreted with caution: we could only show an association, not a causal effect of maternal smoking on brain and behaviour. Such causality can be, and has been, demonstrated only in experimental models.
“It is also important to note that almost half of the children of mothers smoking during pregnancy showed no differences in the brain and behaviour, suggesting that something protected them from the adverse effect of cigarette smoke.”
- Smoking in pregnancy risks psychotic children
Mothers who smoke during pregnancy put their children at greater risk of developing psychotic symptoms as teenagers, British scientists said on Thursday.
Researchers from four British universities studied 6,356 12-year-olds and interviewed them for psychotic-like symptoms such as hallucinations or delusions. Around 19 percent had mothers who smoked during pregnancy.
Just over 11 percent, or 734 of the total group, had suspected or definite symptoms of psychosis.
Many previous studies have shown cigarettes can harm the fetuses of mothers who smoke while pregnant. The risks include causing babies to be born smaller and increasing the risk of sudden infant death syndrome or heart defects.
Stanley Zammit, a psychiatrist at Cardiff University’s School of Medicine who led the study, said the more the mothers smoked, the more likely their children were to have psychotic symptoms.
“We can estimate that about 20 percent of adolescents in this cohort would not have developed psychotic symptoms if their mothers had not smoked,” he said.
Despite countless studies flagging up the risks to babies, it is estimated that between 15 and 20 percent of women in Britain smoke during pregnancy.
The researchers also found drinking during pregnancy was associated with increased psychotic symptoms, but only in children whose mothers had drunk more than 21 units of alcohol a week in early pregnancy.
The reasons for the link between maternal smoking and psychotic symptoms are not clear, but Zammit and colleagues suggested that exposure to tobacco in the womb might affect a child’s impulsivity, attention or cognition.
Only a few mothers in the study, which was published in the British Journal of Psychiatry, said they had smoked cannabis during pregnancy, and this was not found to have any significant link with psychotic symptoms.
- Smoking During Pregnancy can Increase Infant Distress
Studies have consistently found that prenatal cigarette smoke exposure is associated with increased rates of behavior problems, irritability, attention-deficit/hyperactivity disorder, the risk of violent offenses, conduct disorder, adolescent onset of drug dependence, and the risk for criminal arrest in offspring. This study adds another potential negative outcome to the list of reasons for mothers to stop smoking while pregnant.
Most of the effects of tobacco either during pregnancy or on postnatal outcomes are attributed to nicotine. However, smoking is associated with reduced monoamine oxidase A (MAO-A) activity, enzymes that degrade brain neurotransmitters in smokers. Prenatal smoke exposure-induced low MAO-A activity in fetal life may dysregulate brain neurotransmission, creating a potential vulnerability to develop behavioral disorders later in life. This dysregulation can occur with or without interaction with nicotine’s effect on the developing brain.
French scientists compared blood biomarkers of MAO-A activity in smoking and non-smoking pregnant women and in the cord blood of their newborns. They also assessed the newborns’ comfort level during their first 48 hours of life. They found that MAO-A activity is reduced both in pregnant smokers and in their newborns. The newborns of smoking mothers also showed significantly more discomfort than those of non-smoking mothers, potentially related to MAO-A inhibition.
“We know that maternal smoking can negatively affect a newborn in many ways, such as contributing to low birth weight. Berlin and colleagues provide new evidence that the newborns of mothers who smoke experience more behavioral discomfort, and they suggest a mechanism that helps to explain the cause of this discomfort,” commented Dr. John Krystal, Editor of Biological Psychiatry. Although additional studies are needed, this work highlights the importance of targeting pregnant women for help to stop smoking.
- BPA During Pregnancy Linked to Female Aggression
A new study adds to the growing concern that prenatal exposure to the chemical bisphenol A could harm children’s development.
In the study of 249 pregnant women, the first to examine the effects of BPA on children’s behavior, researchers found that girls whose mothers had the highest levels of BPA during pregnancy were more aggressive and hyperactive at age 2 than other girls. Findings appear today in the journal Environmental Health Perspectives.
Girls were more likely to be aggressive if their mothers had high levels of BPA — an estrogen-like chemical used in many consumer products — early in pregnancy or at about 16 weeks, the study says. A typical pregnancy lasts 40 weeks.
The girls had aggression scores that were similar to those of boys, as measured by a commonly used test, says co-author Joe Braun of the University of North Carolina-Chapel Hill. Boys appeared unaffected by BPA.
Braun says he plans to follow children until age 5, because behaviors can change over time.
Michelle Macias, a doctor and spokeswoman for the American Academy of Pediatrics, notes that the increases in aggression were subtle. “Nothing in this study suggests that these kids have higher rates of behavioral disorders,” Macias says.
Hugh Taylor, an obstetrician/gynecologist at Yale University School of Medicine, notes that the new findings closely match the animal studies.
And Taylor says the study raises concerns about the effect of exposing a fetus to an artificial substance that mimics estrogen. Although estrogen is often considered a “female hormone,” it actually helps to “masculinize” the male brain around the 11th and 12th weeks of pregnancy, says neurobiologist Louann Brizendine, author of The Female Brain.
“In the developing brain, timing is everything,” Brizendine says. “I’m worried that tiny amounts of this stuff, given at just the wrong time, could partly masculinize the female brain.”
Co-author Bruce Lanphear, a pediatrician at BC Children’s Hospital in Vancouver, says there’s already enough evidence to show that pregnant women should reduce their exposure to BPA. “We could end up doing a lot of harm by not acting,” he says.
