Research suggests that smoking during pregnancy may increase the risk of cerebral palsy in offspring.
According to the Centers for Disease Control and Prevention (CDC), around 55 percent of mothers who smoke prior to becoming pregnant quit the habit during pregnancy.
However, around 10 percent of expectant mothers in the United States still smoke in the final 3 months of pregnancy.
Smoking during pregnancy is a risk factor for numerous health problems among offspring, including premature birth, birth defects - such as cleft lip, or cleft palate - and sudden infant death syndrome.
The new study - led by Dr. Hui Chen, of the University of Technology Sydney in Australia - teaches us more about the subject.
Smoke exposure and cerebral palsy
Cerebral palsy is a movement and balance disorder that is estimated to affect around 1 in 323 children in the U.S.
The condition is caused by damage to the developing brain. This may occur before birth, during birth, within 1 month of birth, or in a child's early years.
One cause of cerebral palsy is the brain being starved of oxygen-rich blood in the womb, a process known as hypoxia-ischemic injury (HII).
The new research - recently published in the journal Frontiers in Molecular Neuroscience - reveals how exposure to cigarette smoke in the womb can worsen responses to HII, causing cell death in brain regions associated with motor skills and memory, which are regions implicated in cerebral palsy.
The researchers came to their findings by studying mice born to mothers that had been exposed to cigarette smoke before and during pregnancy.
The team tested the motor skills of the mouse pups and found that they demonstrated movement problems similar to those that arise in cerebral palsy.
"We found that pups from smoking mothers are more clumsy at adolescent age, have less strength in their limbs, are more anxious, and have poor memory function which many affect their learning ability," says Dr. Chen.
'Stop smoking long before pregnancy'
On further investigation, the team found that the movement problems seen in the mouse pups were due to an increase in oxidative stress, which is the imbalance between antioxidants and harmful molecules called free radicals.
Dr. Chen explains that HII caused by cigarette smoke exposure prevents mitochondria - which are the "powerhouses" of cells - from producing sufficient amounts of antioxidants, allowing free radicals to accumulate and cause damage to brain cells.
The researchers believe their that findings provide yet another reason for expectant mothers to stop smoking, and they suggest that the earlier smoking is ceased, the better.
"What we have observed so far," says Dr. Chen, "is that in order to avoid harm to their baby, mothers need to give up smoking several months or even years before their pregnancy, as smoking will affect the quality of their eggs before they are even fertilized."
The team now plans to assess whether or not antioxidants could be used to reduce the harms of maternal smoke exposure among offspring; a previous study they conducted indicated that an antioxidant called L-carnitine improved kidney and respiratory function in mouse pups born to mothers exposed to cigarette smoke in pregnancy.
"The next step will be to use such a treatment to improve functional outcomes in pups from the smoking mothers," says Dr. Chen.
"However, the message for the public is if you want a healthy baby, you need to stop smoking long before you plan for the pregnancy."
Dr. Hui Chen