Smoking by Pregnant Mothers During Third Quarter Lowers Birth Weight of Babies

First Posted: Jan 21, 2014 05:55 AM EST

A study focusing on maternal smoking during pregnancy and the damage caused to the fetus reveals that every cigarette smoked during the third quarter lowers the baby's weight by 20 grams.

Smoking during pregnancy has already been established as a major health risk issue for the unborn. This debate on smoking during pregnancy has fired up again after a doctoral dissertation by a Professor at the Catholic University of Valencia 'San Vicente Martir' (UCV) uncovered that every cigarette lit by the mother during the third quarter of pregnancy reduces the baby's weight by 20 grams.

The study led by Professor Rafael Vila,  from the Health Department of La Ribera (Alzira-Valencia),  evaluated 140 pregnant women.

 Studies conducted in the past focusing on infants' exposure to nicotine from both passive and active smoking mothers reveal that the kids develop poor sensory, motor, physiology and attention response. Tobacco consumption by pregnant mothers affects the child's neurobehavioral development and lowers reading scores in kids. Studies also showed how third generation offsprings suffer from chronic lung disease.  

"If a mother smokes for example between 5 and 10 cigarettes a day from the 25th week of pregnancy, the child's weight may be reduced between 100 and 200 grams. This would be worrying in cases where the baby could be affected by underweight," Vila said in a statement.

He also explains that if the mother quits smoking during the first and second quarter, the fetus does not suffer the risk of weight loss. Therefore, a lot of emphasis is given on cessation of smoking during pregnancy, especially at the end.

The subjects were analyzed using a new multivariant predictive model that was designed by Vila and in the  normal-weight category it improves the accuracy of ultrasounds in predicting the birth weight by an average of 10'48 percent.

The projected weight at 40 weeks calculated during the third trimester scan overestimates the birth weight of the infant in 300'89 grams. According to the researcher, there is an average error of 10.75 percent, while the novel predictive model has an average error of 0.54 percent.

 The multivariate regression model uses the regular ultrasound that is performed during the third quarter as a basis. Also it adds multiple variables other than smoking including gestational age, fundable height (measure of the size of the uterus) and serum ferritin levels (body's iron storage protein).

The researcher claims the variable fundal height to be the most accurate in predicting the birth weight of the baby, even beating the ultrasound scanning.

The predictions are based on ultrasound scans conducted in the third quarter of the pregnancy. In this the precision error is reported to be 11 percent. But this accuracy can be enhanced by including other variables especially fundal height.

Through his dissertation entitled "Anthropometric, haematological, obstetric and toxic variables that influence birth weight: a predictive model" Vila shows that the predictive model is practical and not time consuming. 

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