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Editor,—We have been assessing the recent in utero exposure to tobacco smoke in newborns from the Barcelona cohort of the AMICS study (Asthma Multicentre Infants Cohort Study).1The nursing personnel reported observational symptoms suggesting a possible neonatal nicotine withdrawal syndrome in some of the newborns from smoking mothers.
The published data about this syndrome are scant and include conflicting positions. Whereas some papers admit a neonatal nicotine withdrawal syndrome,2 others reject it.3Although some investigators have shown neuroanatomic disorders in fetus and newborns exposed to smoke during pregnancy,4 5 we have not found any study published about the clinical consequences of the withdrawal of nicotine in newborns from a smoke exposed mother before birth.
To achieve a statistically significant evidence on the existence of neonatal nicotine withdrawal syndrome it would be necessary to recruit a very wide cohort of newborns because of the probable very low prevalence rate of pure neonatal nicotine withdrawal syndrome.
We designed a pilot study to assess if neonatal nicotine withdrawal syndrome might exist among newborns exposed to cigarette smoke. We included all the babies born in the Hospital del Mar in Barcelona during a period of six months from mothers smoking at least in the last four weeks before delivery. A sample of urine was obtained from newborns in the first 12 hours of life. Urinary cotinine, the major nicotine metabolite, was measured in duplicate using a double antibody radioimmunoassay.1 The Finnegan clinical score6 was assessed by nursing personnel three times a day for three consecutive days. This test indicates neonatal withdrawal syndrome (positive result) when two consecutive scores over 8 are obtained, whereas a zero score indicates absence of withdrawal syndrome. We excluded newborns with conditions that could change Finnegan test's results, for example, sepsis, prematurity, asphyxia, maternal consumption of substances like coffee, cola beverages, chocolate, or drugs of abuse. Informed consent was obtained in all cases and the study obtained the permission from the local ethical committee.
Thirty three newborns fulfilled all inclusion criteria. The median concentration of urinary cotinine was 195.4 ng/ml. Only six newborns from mothers who declared to smoke less than three cigarettes/day had low levels of urinary cotinine (< 50 ng/ml). In the other cases, range of concentration varied between 123.1 and 1050.2 ng/ml. We did not find any positive result of the Finnegan test. In particular, 22 newborns showed a zero score, 16 of them (72%) with urinary cotinine lower than 195.4 ng/ml. However, we recorded scores between zero and 8, especially by irritability and tremor over the first 24 hours of life, in 11 newborns. These newborns (seven with 1–4 score and four with 5–7 score) presented urinary cotinine in the higher part of the range (median concentration: 412.2 ng/ml) and were from mothers who declared to smoke at least 20 cigarettes/day.
From the results of this pilot study, we conclude that neonatal nicotine withdrawal syndrome seems to be very uncommon. However, the observation of isolated temporary symptoms in newborns from heavy smoker mothers probably suggests an association. Finally, more research on this topic is needed, especially to investigate long term health status in neonates with prenatal exposure to cigarette smoke.