Smoking during pregnancy impacts offspring's reading skills
Yet another adverse outcome of smoking during pregnancy has been reported. In addition to serious outcomes, such as stillbirth, preterm birth, and miscarriage, offspring of mother’s who smoke during pregnancy were found to have lower reading scores in school. A team of international researchers published their findings online on November 5 in the Journal of Pediatrics.
Previous studies have noted that nicotine exposure to developing fetuses is linked to lower IQ scores, academic achievement, and behavioral disorders. However, the authors could find no reports in the medical literature that focused on specific reading tasks such as accuracy and comprehension. Therefore, they conducted a study to determine whether prenatal exposure to nicotine has an impact on several reading skill outcomes in school age children.
The study group comprised 5,119 school age children enrolled in the Avon Longitudinal Study of Parents and Children (ALSPC), which began in the early 1990s in the United Kingdom. The researchers investigated specific reading skill outcomes in the area of speed, fluency, accuracy, spelling, and comprehension in relation to prenatal nicotine exposure. Prenatal nicotine exposure was divided into three categories: high (more than17 mg per day), low (17 mg or less per day), and no exposure. Only data from children with IQ scores of 76 and higher were used. An IQ score of 70 and below can be the sign of a mental disability. The researchers collected questionnaires from mothers before and after giving birth. This made the mother’s reporting more reliable. If mothers knew their child's reading scores beforehand, they might subconsciously report more or less smoking.
After adjusting the data for possible confounding factors, the investigators found that prenatal nicotine exposure was associated with increased risk of underperformance in specific reading skill outcomes. The effect of poor performance in decoding single words was most pronounced among children with prenatal exposure to high levels of nicotine in conjunction with a phonological deficit. (Phonology is a branch of linguistics concerned with the systematic organization of sounds in languages.) In simpler terms, the investigators found that children born to mothers who smoked more than one pack per day struggled on tests specifically designed to measure how accurately a child reads aloud and if he or she understands what she read.
Overall, children exposed to high levels of nicotine in utero ––defined as the minimum amount in one pack of cigarettes per day--scored 21 percent lower in these areas than classmates born to non-smoking mothers. The difference remained even when researchers took other factors into account such as if parents read books to their children, worked in lower-paying jobs or were married. Among students who share similar backgrounds and education, a child of a smoking mother will on average be ranked seven places lower in a class of 31 in reading accuracy and comprehension ability.
The authors concluded that high prenatal nicotine exposure has a negative association with reading performance in school age children. In addition, modeling showed that environmental factors significantly moderated the interaction between prenatal nicotine exposure and reading skill outcomes.
Reference: The Journal of Pediatrics