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Maternal cigarette smoking and oxygen diffusion across the placenta
P G Bush1, T M Mayhew, D R Abramovich
1Department of Biomedical Sciences (Physiology), Medical School, University of Edinburgh, Teviot Place, UK.
Placenta
|November 30, 2000
Summary
Maternal smoking during pregnancy does not increase placental oxygen transport capacity. This constant diffusive conductance, despite fetal hypoxic stress, may reduce the oxygen pressure gradient, contributing to lower birthweights.
Area of Science:
- Obstetrics and Gynecology
- Physiology
- Perinatal Medicine
Background:
- Maternal smoking during pregnancy is linked to intrauterine fetal hypoxia.
- The placenta's role in oxygen transport may adapt to compensate for this stress.
Purpose of the Study:
- To investigate adaptations in placental oxygen diffusive conductances in smokers.
- To determine if these adaptations offset fetal hypoxic stress.
Main Methods:
- Stereological analysis of human term placental tissue from smokers and non-smokers.
- Estimation of partial, total, and specific oxygen conductances using structural and physicochemical data.
- Statistical analysis (ANOVA, t-tests) to compare groups.
Main Results:
- Partial oxygen conductances in maternal erythrocytes and plasma showed apparent improvements in smokers.
- Total and specific placental oxygen conductances did not significantly differ between smokers and non-smokers.
- Elevated fetal hematocrits indicated chronic hypoxic stress in smokers.
Conclusions:
- Placental total oxygen conductance does not increase with maternal smoking.
- Reduced transplacental oxygen partial pressure gradient may occur despite constant conductance, contributing to lower birthweight.