We knew for many years that smoking during pregnancy was harmful for the baby, as it has been linked to increased risk of miscarriage, preterm labor and low birthweight. But a recent study came to incriminate cigarette smoking for something we were not sure yet: birth defects.

British scientists examined the literature published on the subject the last 50 years, and after putting all the information together in what is called a meta-analysis, they came up with the conclusion that smoking is indeed responsible for certain birth defects.

The higher risk was for a malformation called gastroschisis, in which the baby is born with the intestine or stomach protruding outside the body through a hole in the abdominal wall; for this anomaly, babies of women who smoked during pregnancy had 50% increased risk.

In addition, they found that babies born from mothers that smoked while expecting had higher risk for the following:

  • Musculoskeletal defects, that is, missing or shortened arms and legs, cleft lips, cleft palate, craniosynostosis (abnormally shaped head): 26% higher risk;
  • Gastrointestinal malformations: 27% more chances.
  • Undescended testis in baby boys: 13% higher chances.
  • Heart problems: 9% excess risk.

That cigarette is toxic for a developing baby does not seen illogical: cigarettes contain more than 7000!! chemicals, most of which can easily cross the placenta. And we know very well that cigarette is highly toxic for adults and children.

The mechanism by which cigarettes may cause all these defects is not clearly understood, but the key seems to be reduced oxygen supply to the baby. Nicotine (the addictive component of cigarettes) causes blood vessels to constrict, this may lead to reduced blood flow to the placenta or to the baby’s tissues; another component, carbon monoxide, binds to hemoglobin (the molecule that carries oxygen in the blood) stronger than oxygen, thus lowering the amount of oxygen in the blood circulation. Maybe, some of the chemicals contained in cigarette have a direct toxic effect on the baby’s tissues.

In light of this information, if you are a smoker you should make every possible effort to quit smoking as soon as you learn you are pregnant, or even better, before conceiving.

Cigarette is addictive, so it may not be easy, but your baby can give you a great motivation to quit….


Allan Hackshaw, Charles Rodeck, and Sadie Boniface: Maternal smoking in pregnancy and birth defects: a systematic review based on 173 687 malformed cases and 11.7 million controls. Hum. Reprod. Update (2011) doi: 10.1093/humupd/dmr022. First published online: July 11, 2011