Objective: To determine whether maternal smoking and/or alcohol consumption has an influence on lip morphology. Maternal smoking is a known risk factor for orofacial clefts; however, its influence on normal lip variation is unknown. Recent research regarding normal lip morphology has been contradictory.
Design: Retrospective cohort study.
Setting and participants: A total of 4747 children from the Avon Longitudinal Study of Parents and Children (ALSPAC) who each had 3D facial scans carried out at 15 years of age were included in the study.
Methods: Each of the participants was automatically categorised regarding predetermined lip morphological traits. Questionnaires completed by their mothers identified smoking and alcohol habits during pregnancy. Logistic regression analyses were applied to determine the effect of maternal smoking and alcohol consumption on lip morphology.
Results: Maternal smoking has significant effects on upper and lower lip contours, Cupid's bow, lower lip-chin shape and lower lip tone (all P < 0.05). There was also an indication of a potential epigenetic effect of smoking pre-pregnancy on upper lip contour (P = 0.0573). Alcohol consumption is significantly associated with philtrum shape, particularly when >6 units of alcohol are consumed per week (P = 0.0149, 32 weeks). Overall results suggest a deeply grooved philtrum is more likely if alcohol is consumed. Investigating the combined effect of smoking and alcohol consumption, lower lip contour (P = 0.00923) and lower lip-chin shape (P = 0.0171) are statistically significant, with lower lip contour more likely to be narrow in the midline, and lower lip-chin shape more likely to be an angular concavity.
Conclusion: Maternal smoking influences a number of lip traits, including a possible epigenetic effect on upper lip contour. Maternal alcohol consumption, particularly at a high level, influences philtrum shape. Maternal smoking and alcohol consumption have a combined effect on lower lip contour and lower lip-chin shape.
Keywords: 3D imaging; ALSPAC; facial morphology; facial shape; imaging and cephalometry; lip morphology; lip shape; maternal alcohol; maternal smoking.