The Research Question would be “Are babies born from mothers who smoke during the pregnancy have greater chances of developing low-birth weight, compared to those born from mothers who do not smoke?”
A study was conducted on pregnant women that belonged to a Maternity Hospital in Haguenau, France, in 1974. 248 pregnant women that smoked at least five cigarettes a day were defined as ‘cases’, and 196 pregnant women who did not smoke were defined as ‘controls’.
Tests conducted on the placenta demonstrated higher incidences of defective trophoblasts in smokers compared to non-smokers. The signs of intrauterine hypoxia, low birth-weight and low placental weight, were also higher in smokers compared to non-smokers. However, the study was not able to establish a relationship between low birth-weight and low placental weight or intrauterine hypoxia (Shipra, A. Et al, 1977).
Another study conducted demonstrated that mothers who smoked during one pregnancy had produced infants with lower birth-weight, compared to those infants born during pregnancy when they did not smoke. This was irrespective of the birth order and other factors that affect the growth of the unborn baby in the utreus. The reduction in the birth weight was directly associated with the number of cigarettes smoked.
Mothers, who smoked less, produced infants on an average 90 grams less than normal, whereas those who smoked heavily developed babies on an average 533 grams below normal. Smoking brought about the development of several lesions in the placental due to under-perfusion (which was usually periodic). Besides, pregnancy during smoking was on an average 1.5 days shorter than without smoking (Naeye, R.L., 1978).
A study was also able to demonstrate that women who quit smoking during pregnancy are able to reduce the several risks associated with pregnancy such as low birth-weight, preterm labor, spontaneous abortion, etc, and period of breastfeeding also improved (Giglia, R.C. Et al, 2006).
A study conducted in Johannesburg and Sweto, in 1990, demonstrated that women who smoked (6.1%) and used snuff (7.5%) during the pregnancy, produced babies who weight an average 2982 grams compared to babies of non-smokers who weighted 3148 grams, on an average. However, environmental pollutants (such as passive smoking) did not significantly adversely affect the birth weight (Steyn, K., Et al, 2006).
Another study conducted in Pelotas, Brazil, in 193, demonstrated that smoking in mothers produced babies on an average 142 grams below that of the non-smokers average. The study also demonstrated that the risk of fetal retardation was higher with the extent of smoking. However, the study did not find any relationship between preterm delivery and smoking (Horbta, H.L. Et al, 1997).
Hence, it is obvious that birth-weight of the baby is directly affected to the extent of smoked (number of cigarettes) by the mother during pregnancy. Further studies need to be conducted on the exact manner in which smoking causes a reduction in the birth-weight of the child.
References:
Giglia, R.C., Binns, C.W., & Alfonso, H.S. (2006). Which women stop smoking during pregnancy and the effect on breastfeeding duration. BMC Public Health, 2696Z), 195.
https://www.ncbi.nlm.nih.gov/pubmed/16869976?dopt=AbstractPlus
Horta, B.L., Victora, C.G., Menezes, A.M., Halpern, R., & Barros, F.C. (1997). Low birthweight, preterm births and intrauterine growth retardation in relation to maternal smoking. Paediatr Perinat Epidemiol, 11(2), 140-151. https://www.ncbi.nlm.nih.gov/pubmed/9131707?dopt=abstractplus
Naeye, R. L. (1978). Effects of maternal cigarette smoking on the fetus and placenta. Br J Obstet Gynaecol, 85(10), 732-737.
https://www.ncbi.nlm.nih.gov/pubmed/708656?dopt=abstractplus
Spira, A., Philippe, E., Spira, N., Dreyfus, J., & Schwartz, D. (1977). Smoking during pregnancy and placental pathology. Biomedicine, 27(7Z), 266-270.
https://www.ncbi.nlm.nih.gov/pubmed/588667?dopt=Abstract
Steyn, K., de Wet, T., Saloojee, Y., Nel, H., & Yach D. (2006). The influence of maternal cigarette smoking, snuff use and passive smoking on pregnancy outcomes: the Birth to Ten Study. Paediatr Perinat Epidemiol, 20(2), 90-99.
