Influence of maternal smoking during pregnancy on oxidant status in amniotic fluid

Approximately 20% of women in Germany are smokers, and some of them are unable to stop smoking during pregnancy. As cigarette smoke generates free radicals, it has been suggested that it may be one of the major sources of oxidant stress in pregnant women and unborn fetuses. On the other hand, the human placenta is known to be a major source of pro-oxidant agents, antioxidant enzyme systems, and hormones, and is able to keep lipid peroxidation under control in normal pregnancy. The aim of the present study was to determine whether it is possible to detect antioxidants in amniotic fluid using the Esterbauer method and to analyze whether there are any differences in the oxidant status of the amniotic fluid between smoking and non-smoking mothers. The results were confirmed by two assays measuring the total antioxidant capacity (TAC), as well as the malon dialdehyde concentration (MDA) in the amniotic fluid of smoking and non-smoking mothers.

Differences in low-density lipoprotein (LDL) susceptibility to oxidation were measured using the Esterbauer method in the amniotic fluid of smoking and non-smoking mothers.

The results showed that there was a significant difference in the duration of susceptibility of LDL to oxidation between smokers and non-smokers (49.47 ± 24.78 min, n=20 and 31.94 ± 14.26 min, n=67; p=0.006). Arithmetic average of MDA was higher in smokers than in non-smokers (11 pmol/mg and 6 pmol/mg); for TAC it was vice versa 840 mM vs. 1054 mM.

Measuring the lag phase of LDL oxidation makes it possible to study antioxidative effects. As the lag phase was significantly longer in smokers than in non-smokers, it can be assumed that there must be a substance in the amniotic fluid of smokers which has antioxidative power, inhibits LDL oxidation, and intercepts radicals. It can be assumed that the fetoplacental unit has mechanisms to react against tobacco smoke inhaled by the mother.