Carbon Monoxide May Help Prevent Debilitating Pregnancy Condition

The study was precipitated by the fact that mothers who smoke cigarettes during pregnancy have a 33 per cent decreased risk of developing pre-eclampsia compared to nonsmokers.

A debilitating condition that affects five to seven per cent of pregnancies, pre-eclampsia is characterized by high blood pressure in pregnant women and is one of the leading causes of baby and maternal deaths. "At present there is no cure or effective treatment for this condition, other than delivery of the baby," says research team leader Dr.Graeme Smith (Obstetrics and Gynecology), an expert in high-risk obstetrics.

In the Queen's study, published in the September issue of the American Journal of Pathology, tissue from the placentas of nonsmoking women who had delivered babies by caesarian section was exposed to the same kind of oxidative stress -- not enough oxygen being supplied through the blood -- experienced by women with pre-eclampsia. When the tissues were treated with carbon monoxide, at levels similar to those found in the blood of smoking mothers, cell death in the placenta was significantly reduced.

"We believe that carbon monoxide found in cigarette smoke, and subsequently carried in a smoking mother's blood, may be the cause of their lower risk of developing pre-eclampsia," says Dr. Smith. He stresses however that any perceived benefit of smoking during pregnancy is outweighed by the many risks: premature membrane rupture, preterm delivery, stillbirth, low birth weight, and sudden infant death syndrome.

Produced naturally by the body at low levels, carbon monoxide relaxes blood vessels and may prevent the death of placental cells, which can cause injury to fetus and mother. Future studies will determine whether carbon monoxide can prevent placental cell death in animal models and whether other approaches similar to carbon monoxide may provide protection.

Also on the research team, from Queen's Department of Anatomy and Cell Biology, are: Shannon Bainbridge, Louiza Belkacemi, Michelle Dickinson, and Charles Graham.

The work was supported by the Strategic Training Initiative in Research in Reproductive Health Sciences, the Heart and Stroke Foundation of Ontario, and the Canadian Institutes of Health Research.