The reduced production of the vasodilator nitric oxide (NO) in fetal vessels in pregnant smokers is the explanatory variable in the research, result in lower birth weight, length, and head circumference is the response variable while the confounding variable is the reduction of
blood flow to the foetus. The reduced production of the vasodilator nitric oxide (NO) in fetal vessels in pregnant smokers is the treatment. The observatory units for the research are people who are smokers, non-smokers and ex-smokers who are volunteers.
The research was carried out by observing the new born babies delivered by the three set of volunteers (smokers, non-smokers and ex-smokers) observing the babys weight, head circumference and their size. The result found was that Newborns of smokers had a lower weight (P_0.001) and a smaller head circumference (P_0.041) and were shorter (P_0.001) than newborns of nonsmokers and ex-smokers. eNOS activity in umbilical veins of smokers was 36 lower (P_0.001), eNOS concentration was 47 lower (P_0.001), and the fetal plasma level of high-density lipoprotein was 18 lower (P_0.001) than those of nonsmokers, whereas the same levels were found in umbilical veins from ex-smokers and nonsmokers(Anderson et al). This lead to the conclusion that maternal smoking reduces eNOS activity in the fetal vascular bed, contributing to retarded foetal growth which is as a result of the reduction of vasodilatory capacity, and suggest that cessation of smoking early in pregnancy prevents these effects in newborns. I agree with the conclusion of the author as the research was well carried out, with the author following the right process required of an observational research.