"The profound effects of smoking on
fetal development are irreversible and may cause impairment in the
health and well-being of the offspring in later life," said Dr.
Peter Hindmarsh at the British Endocrine Societies annual meeting in
"In particular, the reduced brain
size that we saw in smokers' babies could lead to impaired cognitive
ability of the child," he said.
Hindmarsh and colleagues at
University College London studied 1,650 expectant mothers, including
about 200 smokers, throughout their pregnancy.
They measured blood flow between the
fetus and placenta and monitored levels of a group of hormones
called insulin-like growth factors (IGF), which are essential for
fetal growth and organ development. After birth, the researchers
weighed the newborns and measured their head size, which is an
indicator of brain size.
The harm caused by smoking during
pregnancy is well known, but this was the first study to put
together all the elements of reduced blood flow, IGF levels and
fetal growth, Hindmarsh told Reuters Health.
The researchers found that blood
flow in the artery joining the fetus to the placenta was lower in
women who smoked, causing damage to the placenta and restricting the
delivery of essential nutrients.
They also showed that the amount of
IGF in umbilical cord blood was reduced according to how many
cigarettes the mother smoked. For example, IGF-1 levels were an
average of 70.2 nanograms per milliliter of blood in nonsmokers,
compared to 60.7 nanograms in women who smoked 20 cigarettes or more
"What we're talking about are
reductions of about 10 to 15 percent (in IGF levels), producing
rather similar reductions in overall birth size, birth length and
head growth," Hindmarsh told Reuters Health.
Low birth weight has been linked to
a number of health conditions in adulthood, including an increased
risk of high blood pressure, diabetes and infertility.
The latest study also included a
group of women who only quit smoking when they discovered they were
pregnant. Placental function, IGF levels and the size of the babies
were all normal for those women, Hindmarsh said (wow - now
"This shows it is worth thinking
about stopping, because even in a very short time like pregnancy you
aren't going to set the baby up for the same sort of problems as if
you persist," he said.