Study: Smoking During Pregnancy Impairs Fetal Development

British research finds that women who smoke during pregnancy risk having smaller babies with smaller brains, Reuters reported March 24.

According to researchers at University College London, smoking damages the placenta and reduces levels of a critical growth hormone.

"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, lead author of the study. "In particular, the reduced brain size that we saw in smokers' babies could lead to impaired cognitive ability of the child."

The study involved 1,650 expectant mothers, including 200 who smoked throughout their pregnancy. The researchers measured blood flow between the fetus and placenta and monitored levels of insulin-like growth factors (IGF), a group of hormones essential to fetal growth and organ development.

After birth, the researchers weighed the newborns and measured their head size to determine brain size.

The study found that blood flow in the artery joining the fetus to the placenta was lower in women who smoked. This resulted in damage to the placenta and restricted the delivery of essential nutrients.

In addition, there was a lower amount of IGF in umbilical-cord blood among women who smoked. The levels varied, based on how many cigarettes the mother smoked.

"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," said Hindmarsh.

Hindmarsh presented the study's findings at the annual meeting of the British Endocrine Societies, held recently in Glasgow, Scotland.