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What is the influence of prenatal second-hand smoke exposure on infant self-regulation?

Research indicates that prenatal second-hand smoke (SHS) exposure, also referred to as environmental tobacco smoke exposure (ETS), increases the risk of various neurodevelopmental problems in children. However, 12 states in the US still lack public smoking laws.

Study: Associations between prenatal exposure to second hand smoke and infant self-regulation in a New York city longitudinal prospective birth cohort. Image Credit: Lion Day/Shutterstock

A new study in Environmental Research aimed to analyze an important gap concerning the impact of prenatal SHS exposure on infant self-regulation.


Nicotine can cross the placenta and bind with the nicotinic receptor that impacts the development and functions of cholinergic and dopaminergic systems leading to changes in attention, hyperactivity, and inhibitory control in rodents. SHS also comprises heavy metals that can result in altered self-regulation in children.

Additionally, active maternal smoking in pregnancy has been associated with self-regulation difficulties, altered self-regulatory structure, and function of neural circuitry in children.

Early life and prenatal exposure to SHS has also been associated with altered function of frontostriatal circuits, increased hyperactivity, and externalizing behaviors among pre-school age and 5 to 6 years old children. However, how early the effects of SHS manifest and whether they can be detected during infancy is unknown.

Self-regulation is an important part of development that indicates the capacity of one’s emotions, behaviors, and thoughts. An individual’s self-regulatory capacity can be determined through age-sensitive measurement approaches.

Infant self-regulation is determined using the ratio of infant behavioral self-contingency and the degree of stability or variability within an individual’s behavior rhythm. Infants can process sequences and contingencies of behavior and develop expectancies based on such contingencies.

Developing infants have been reported to have predictable self-contingency patterns of emotion, attention, infant-initiated touch, and head orientation. Self-contingency is mostly neutral, and lower self-contingency indexes indicate a less predictable and more varying process, while higher self-contingency indexes indicate a more predictable and less varying process.

About the study

The study involved participants in the Fair Start birth cohort at the Columbia Center for Children’s Environmental Health (CCCEH). The Fair Start Study involved recruiting pregnant women who received prenatal care, were 18 years and above, spoke Spanish or English, and mostly self-identified as Hispanic.

The enrolled participants were then invited for a study visit to assess mother-infant interaction at the infant age of 4 months. The current study involved the first 99 mother-infant dyads who completed the 4-month visit as well as had data on environmental tobacco smoke exposure.

Assessment of SHS took place through a self-report questionnaire during a prenatal visit. Infant or mother self-regulation was initiated by behavioral self-contingency. This was followed by the analysis of face-to-face interaction of the mother and infant since four months is suitable for assessing infant social development.

Two video cameras were used that generated a view of the upper torsos of infants seated in infant seats and mothers who were seated opposite. Three communication modalities were analyzed for infants, including vocal effect, facial affect, and gaze, and three for mothers, including touch, gaze, and facial affect.

Time-series models were used to assess the course of behavior second-by-second within and between individuals, followed by weighted-lag time-series analysis and individual-seconds time-series models. Behavioral codes were generated for both infants and mothers according to their predicted behavior.

Study findings

The results indicated that out of the 99 mother-infant dyads who had prenatal SHS data and completed the 4-month face-to-face visit, most mothers were Black and/or Latino. Self-contingency was reported to be lower in infants with prenatal SHS exposure across all the modality pairings. Infants with prenatal SHS exposure were observed to transform to less negative facial or more positive vocal affect codes.

Infants with prenatal SHS exposure were also reported to have a higher probability of moving to gaze-off when they had gaze-on as well as the other way around. They also had a more variable cross-modal contingency in facial affect predicting vocal effect.

Self-contingency was reported to be lower in mothers with SHS exposure during pregnancy in 2 modalities, mother’s facial affect was analyzed concerning infant vocal effect and infant gaze. Mothers with SHS exposure were also more likely to transform to less negative/more positive facial affect, similar to infants. However, mother self-continency was reported to be higher in 2 modalities; mother touch analyzed concerning infant-vocal effect, as well as concerning infant gaze.

Infant interactive contingency was reported to be higher in infants with rental SHS exposure in two models; infant gaze was analyzed concerning mother-facial effect and concerning mother touch. Mother interactive contingency was reported to be higher in two modalities, mother facial affect analyzed concerning infant vocal effect and mother touch concerning infant gaze.

Moreover, infants with SHS exposure were observed to be more silent than non-exposed. Mothers with SHS exposure were observed to use more ‘mild smile’ and less’ interest increment.’


The current study demonstrates that exposure to SHS among infants can result in dysregulated behavior. This can negatively impact future child development. This study uses self-regulation as a transdiagnostic marker of future psychiatric problems. Linking self-regulation to prenatal chemical exposure can help to improve public health prevention programs which may reduce such exposures.


It is important to note that the study had several limitations, including; a small sample size, SHS being measured by self-report and not validated by biomarker data, and the study could not control for potential cofounds such as postnatal SHS exposure along with pre- or postnatal exposure to household or ambient air pollutants that were also associated with self-regulation.

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