January 22nd, 2010 
Women who smoke marijuana during pregnancy may impair their baby’s growth and development in the womb, a new study suggests.
Poor fetal growth and reduced head circumference at birth are linked to an increased risk of problems with thinking, memory and behavior in childhood. Cigarette smoking during pregnancy is known to impair fetal growth, but studies on the potential effects of marijuana have been inconclusive.
For the new study, researchers in the Netherlands followed more than 7,000 pregnant women, 3 percent of whom acknowledged smoking marijuana at least during early pregnancy. They found that babies born to marijuana users tended to weigh less and have smaller heads than other infants.
What’s more, the study found, the longer a woman had used marijuana during pregnancy, the stronger the impact on birth size – suggesting that the drug itself was to blame.
And while most marijuana users in the study also smoked cigarettes, the drug appeared to have effects over and above those of tobacco. In fact, marijuana showed stronger effects on birth size than tobacco, the investigators report in the Journal of the American Academy of Child and Adolescent Psychiatry.
The findings suggest that marijuana use, even restricted to early pregnancy, may have irreversible effects on fetal growth, write the researchers, led by Hannan El Marroun of Erasmus University Medical Center in Rotterdam.
The study included almost 7,500 pregnant women who were surveyed on their use of alcohol, tobacco and drugs, and had ultrasounds to chart fetal growth during the first, second and third trimesters.
Overall, 214 women said they had used marijuana before and during early pregnancy; 81 percent quit after learning they were pregnant, but 41 women continued to smoke marijuana throughout pregnancy.
The researchers found that, on average, marijuana users gave birth to smaller babies, particularly those who had used throughout pregnancy.
Women who had smoked only during early pregnancy had babies who were 156 grams — about 5.5 ounces — lighter than infants born to women who had not used the drug. Women who had continued to smoke past early pregnancy had babies who were 277 grams, or nearly 10 ounces, smaller.
Based on ultrasound, marijuana use only in early pregnancy impaired fetal growth by about 11 grams per week, while use throughout pregnancy slowed fetal growth by roughly 14 grams per week. That compared with a deficit of 4 grams per week with tobacco use, the researchers found.
Similar patterns were seen when the researchers looked at fetal head circumference.
According to El Marroun’s team, mothers’ marijuana use could stunt fetal growth for several reasons. Like tobacco smoking, it may deprive the fetus of oxygen. It is also possible that the byproducts of marijuana directly affect the developing nervous and hormonal systems of the fetus.
Finally, the researchers note, pregnant women who use marijuana may have other factors in their lives – such as a less-than-healthy diet or chronic stress — that could contribute to poor fetal growth.
Related
- Natural Delivery OK in Cases of Intrauterine Growth Restriction
Waiting for natural birth is as effective as inducing labor in pregnant women with intrauterine growth restriction (IUGR), a new study shows.
IUGR, which affects about 10 percent of pregnant women, means that the fetus is much smaller than normal. At birth, these babies are more likely to have low blood sugar, an abnormally high red blood cell count and trouble maintaining their body temperature. These babies are also at increased risk for jaundice, infections and cerebral palsy.
Later in life, people who were restricted-growth babies may be more prone to behavioral disorders, obesity, heart disease, type 2 diabetes and high blood pressure.
Currently, doctors have two main approaches for women with suspected IUGR who are nearing delivery. Some doctors induce labor because they’re concerned about complications, while others await natural delivery.
This study compared the effectiveness of the two strategies among 650 women in The Netherlands. The researchers found that median birth weight was significantly lower among babies born after induced labor (2,420 grams) than among those in the spontaneous delivery group (2,560 grams). Both groups of babies had similar rates of adverse post-delivery outcomes.
The findings show that waiting for birth is equally as effective as inducing labor, the researchers concluded.
- Mom’s Lifestyle in Early Pregnancy Affects Baby’s Size
The lifestyle habits you bring into pregnancy can have lasting effects on your baby’s health, new research shows.
A Dutch study found that women who smoked, had high blood pressure or low folic acid levels in early pregnancy had babies that were smaller in the first trimester of pregnancy and had a higher risk of complications later.
“Our study demonstrates that several maternal physical characteristics and lifestyle habits, such as smoking and non-use of folic acid supplements, affect first-trimester fetal growth,” said study senior author Dr. Vincent Jaddoe, a pediatric epidemiologist at Erasmus Medical Center in Rotterdam, the Netherlands.
“First-trimester growth restriction is associated with higher risks of adverse birth outcomes and accelerated postnatal growth rates. Thus, the first trimester of pregnancy seems to be a very critical period for fetal growth and development. This is important, since it suggests that the fetus is already affected before pregnant women visit their midwife or obstetrician,” he said.
For the study, published in the Feb. 10 issue of the Journal of the American Medical Association, the researchers followed 1,631 pregnant women from their first trimester through their pregnancies. The growth of their offspring was assessed until the children were 2.
The average age of the mothers was 31, and 71 percent were white. More than half had a higher than high school education. The average body mass index was 23.5, which is normal (over 25 is considered overweight). About one-quarter smoked at the start of the study.
The researchers found that certain factors affected the likelihood that a fetus would have a small crown to rump length (a standard way to measure babies using ultrasound). Babies whose mothers smoked or had higher diastolic blood pressure readings (diastolic is the bottom number in blood pressure) were more likely to be smaller. Women who didn’t use folic acid supplements and those with higher levels of red blood cells also had smaller babies, according to the study.
A small size during the first trimester translated to a higher risk of certain complications later in the pregnancy, such as preterm birth and low birth weight.
Babies that had first-trimester growth restriction had 7.2 percent odds of being born preterm compared to 4 percent for babies who weren’t growth-restricted. Odds of low birth weight were 7.5 percent for growth-restricted babies compared to 3.5 percent for other babies. And, the odds of being born small-for-gestational-age were 10.6 percent for babies who were growth-restricted compared to 4 percent for babies who grew normally during early pregnancy.
Jaddoe and Dr. Gordon Smith, author of an accompanying editorial in the same issue of the journal, believe that when a woman is exposed to poor lifestyle habits in early pregnancy, it may affect development of the placenta, which then affects the fetus’ ability to survive and thrive.
The bottom line for women is that it’s important to go to the doctor before getting pregnant to find out what steps to take to ensure that you’re in the best shape possible before you get pregnant, such as quitting smoking and taking folic acid supplements.
- Exposure to passive smoking during pregnancy ‘increase children’s risk of cancer in later life’
Pregnant women subjected to passive smoking give birth to babies with an increased, lifelong susceptibility to cancer, research reveals.
Passive smoking causes the same type of genetic damage in unborn infants as that found in adult smokers with cancerous tumors.
Researchers said the abnormalities in newborns were indistinguishable from those found in babies of mothers who were active smokers.
And they may affect survival, birth weight and lifelong susceptibility to diseases like cancer, according to the study published online in the Open Paediatric Medicine Journal.
Dr Stephen Grant and colleagues at the University of Pittsburgh in the U.S. found a smoke-induced mutation in an oncogene, a gene which transforms normal cells into cancerous tumors.
The mutation was the same level and type in newborns of mothers who were active smokers as those in babies born to non-smoking mothers exposed to tobacco smoke.
The mutations were also discernible in newborns of women who had stopped smoking during their pregnancies, but who did not actively avoid second-hand smoke.
The study confirms previous research in which Dr Grant discovered evidence of genetic abnormalities in babies whose mothers were exposed to environmental tobacco smoke.
There is also evidence that maternal exposure to passive smoke, as well as a history of paternal cigarette smoke exposure, is linked with an increased risk of childhood cancer, especially leukaemias and lymphomas in children under five.
Dr Grant said: ‘These findings back up our previous conclusion that passive, or secondary, smoke causes permanent genetic damage in newborns that is very similar to the damage caused by active smoking.
‘By using a different laboratory test, we were able to pick up a completely distinct yet equally important type of genetic mutation that is likely to persist throughout a child’s lifetime.
‘Pregnant women should not only stop smoking, but be aware of their exposure to tobacco smoke from other family members, work and social situations.’
- 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.
