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Acute Effects of Smoking in the
Hemodynamics of Fetal-
Maternal-Placental Unit

Zielinsky, P.; Müller. J.S.; Antunes, M.;
Behle, I.; Teixeira, L.

Fetal Cardiology Unit, Institute of Cardiology of
Rio Grande do Sul. Porto Alegre, Brasil

Background: Tobacco is the most frequently used drug during pregnancy. Maternal smoking causes an increase in vasoactive substances and a decrease in vasodilating substances in the umbilical cord, which may be related to acute and chronic perfusion changes in the fetal-maternal-placental unit.
The purpose of this study was to evaluate acute changes in the fetal-maternal placentary unit after maternal exposure to tobacco.

Material and Methods: Twenty one chronic smokers with a normal gestation, without risk factors for fetal diseases were submitted to obstetric ultrasound evaluation and to fetal echocardiography, before and after smoking a cigarette with a standard concentration of nicotine of 0.5mg and 6mg of carbon monoxide. Mean gestational age was 30.20 weeks. The mean amount of daily used cigarettes was 9.67. The study had been approved by the institutional ethics committee and written consent was obtained from each woman.

Results: Results obtained before and after maternal smoking showed an increase in maternal systolic blood pressure (p=0.004) and in diastolic blood pressure (p=0.033). There was an increase in maternal heart rate (p<0.001) and in fetal heart rate (p=0,044). A decrease in S/D ratio in the left uterine artery (p=0.039) and in the right uterine artery (p=0.014) immediately after smoking was recorded. The S/D ratio in the fetal middle cerebral artery did not change (p=0.078), as well as in the ductus arteriosus (p=0.154), and in pulmonary artery (p=0.958). There was no significant change in the S/D ratio of the umbilical artery (p=0.554), in the left ventricular ejection fraction (p=0.943) and in the redundancy index of the septum primum (p=0.836).

Conclusion: Exposition to smoking during pregnancy affects maternal and fetal physiologic variables without changes in fetal heart function. The observed decrease in uterine vascular resistance is probably related to a dose-dependent action of nicotine and other cigarette components.



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2nd Virtual Congress of Cardiology

Dr. Florencio Garófalo
Steering Committee
Dr. Raúl Bretal
Scientific Committee
Dr. Armando Pacher
Technical Committee - CETIFAC

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