When Parents Smoke, Baby Is Smoker as Well

LEICESTER, England, June 20 -- Infants with at least one parent who smoked had 5.5 times higher urine levels of cotinine a metabolite of nicotine, than babies of non-smoking parents, researchers here reported.

A smoking mother was the major nicotine vector. A mother who smoked had the largest independent effect on accumulation of cotinine, essentially quadrupling urine cotinine levels, Mike P. Wailoo, M.D., of the University of Leicester, and colleagues, reported online in the June Archives of Disease in Childhood.

Having a smoking father doubled the urine cotinine level, they reported.

The damage to infants and young children from smoking parents doesn't stop in pregnancy but continues into the baby's early days of life, increasing the risk of delayed postnatal physiological maturation and possibly cardiorespiratory damage, they noted.

Nearly 40% of children under five in the U.S. are believed to be exposed to tobacco smoke at home, and 6,000 deaths a year in young children may ensue because of this, the researchers wrote.

The findings came from postnatal development studies done over five years through 1998. For this study the infants were recruited sequentially from a database according to whether their parents smoked. On average, each parent smoked 16 cigarettes a day.

Cotinine excretion in urine was assessed in 104 infants, 71 of them with at least one parent who smoked while 33 had parents who were nonsmokers. Cotinine was measured around 12 weeks.

On average, babies with at least one parent who smoked excreted 5.58 (CI 3.4 to 9.5) times as much cotinine in the urine as did infants from non-smoking parents (P<0.001).

Maternal smoking in the household was the largest contributing factor with a four-fold increase (ratio of geometric means 3.97 (95% CI 2.28 to 6.92; P<0.001).

For paternal smoking the increase was almost double (ratio 1.83, CI 1.05 to 3.18; P=0.034).

Sleeping with parents (P=0.037) and rooms with a lower temperature (P=0.028) were also associated with increased cotinine levels, the researchers reported. Other factors, such as social class and feeding method, had no effect.

The proportion of babies who slept in the same room and in the same bed was not different between the smoking and nonsmoking groups.

Babies with high nicotine levels tended to come from poorer homes, which may have smaller rooms and inadequate heating, the researchers said. A suggestion of summer-winter seasonality in the study could mean that higher cotinine levels in colder times of the years may reflect poorer ventilation or a tendency for parents to smoke indoors.

Sleeping with a parent is a known risk factor for sudden infant death syndrome, and the authors suggested that one reason for this could be direct inhalation during sleep or closeness of clothing or other objects contaminated with smoke particles.