The higher the cotinine levels in a mother's blood during pregnancy, the greater was her child's risk of developing attention deficit hyperactivity disorder or ADHD later in life, an epidemiological study by the Research Centre for Child Psychiatry at the University of Turku in Finland has shown.
Globally, it is the first study in which the connection between fetal nicotine exposure and diagnosis of ADHD was shown by measuring cotinine levels from pregnant maternal serum specimens. The research was recently published in the journal Pediatrics.
Despite its proven negative effects on fetal development, smoking during pregnancy remains a significant public health issue. During 2017, approximately 12.5% of all pregnant women in Finland smoked during pregnancy and 7% continued to smoke throughout their pregnancy.
Adverse perinatal outcomes
Exposure to maternal smoking is associated with various adverse perinatal outcomes. An association between maternal smoking and offspring ADHD has been shown in several studies.
However, the causality of the association has been questioned to be mostly due to familial confounding, says Adjunct Professor Roshan Chudal from the Research Centre for Child Psychiatry at the University of Turku.
All previous studies on the topic were based on maternal self-reporting of smoking, which has been shown to underestimate the true rates of smoking. The disclosure of smoking is even lower among pregnant smokers, continues Dr Chudal.
Cotinine reveals connection between smoking and offspring ADHD
Cotinine is the biomarker indicating nicotine exposure. This includes active smoking as well as nicotine exposure from other sources such as nicotine replacement therapy or passive smoking.
Measuring cotinine levels from maternal serum specimens collected during pregnancy, this study investigated the association between nicotine exposure during pregnancy and offspring ADHD.
This study included 1,079 ADHD cases and an equal number of matched controls born between 1998 and 1999. Maternal cotinine levels were measured from maternal serum specimens collected during the first and second trimesters of pregnancy and archived in the national biobank.
The strength of the research is the availability of valuable information from the Finnish Maternity Cohort biobank (FMC).
A strong association
In this first nationwide study using maternal cotinine levels, we report a strong association between prenatal nicotine exposure and offspring ADHD says Professor Andre Sourander, the leader of the research group from the Research Centre for Child Psychiatry.
The World Health Organization (WHO) considers smoking one of the main public health concerns worldwide.
Given the high prevalence of both smoking during pregnancy and ADHD among children, these findings warrant future studies on the interplay between maternal smoking and environmental, genetic, and epigenetic factors, observes Professor Sourander.
Prenatal Cotinine Levels and ADHD among Offspring
Andre Sourander, Minna Sucksdorff, Roshan Chudal, Heljä-Marja Surcel, Susanna Hinkka-Yli-Salomäki, David Gyllenberg, Keely Cheslack-Postava and Alan S Brown
An association between maternal smoking during pregnancy and offspring attention-deficit/hyperactivity disorder (ADHD) has been shown across several studies based on self-reports. No previous studies have investigated the association of nicotine exposure measured by cotinine levels during pregnancy and offspring ADHD.
In this population-based study, 1079 patients born between 1998 and 1999 and diagnosed with ADHD according to the International Classification of Diseases and 1079 matched controls were identified from Finnish nationwide registers. Maternal cotinine levels were measured by using quantitative immunoassays from maternal serum specimens collected during the first and second trimesters of pregnancy and archived in the national biobank.
There was a significant association between increasing log-transformed maternal cotinine levels and offspring ADHD. The odds ratio was 1.09 (95% confidence interval [CI] 1.06–1.12) when adjusting for maternal socioeconomic status, maternal age, maternal psychopathology, paternal age, paternal psychopathology, and child’s birth weight for gestational age.
In the categorical analyses with cotinine levels in 3 groups, heavy nicotine exposure (cotinine level >50 ng/mL) was associated with offspring ADHD, with an odds ratio of 2.21 (95% CI 1.63–2.99) in the adjusted analyses. Analyses by deciles of cotinine levels revealed that the adjusted odds for offspring ADHD in the highest decile was 3.34 (95% CI 2.02–5.52).
The study reveals an association with and a dose-response relationship between nicotine exposure during pregnancy and offspring ADHD. Future studies incorporating maternal smoking and environmental, genetic, and epigenetic factors are warranted.
[link url="https://www.utu.fi/en/news/press-release/maternal-smoking-during-pregnancy-increases-risk-of-adhd-among-offspring-up-to-3-fold"]Study shows connection between maternal smoking during pregnancy and offspring ADHD[/link]
[link url="https://pediatrics.aappublications.org/content/143/3/e20183144.full"]Prenatal Cotinine Levels and ADHD Among Offspring[/link]