Abstract
Objectives A systematic review and meta-analysis to determine the association between active maternal smoking and cleft lip and palate etiology. Data sources Medline, Embase, Web of Science and the Cochrane Library from inception to November, 2020. Study selection Observational studies of cigarette smoking habits in pregnant women. Outcomes included cleft lip and/or palate, cleft lip ± palate and cleft palate only. Data analysis Publication bias analyses were performed and the Newcastle Ottawa scales were used to assess study quality. Fixed or random effect models were used in the meta-analysis, dependent on risk of statistical heterogeneity. Results Forty-five studies were eligible for inclusion of which 11 were cohort and 34 were case–control studies. Sixteen studies were of sufficient standard for inclusion in the meta-analysis. The summary odds ratio for the association between smoking and cleft lip and/or palate was 1.42 (95%CI 1.27-1.59) with a population attributable fraction of 4% (95%CI 3%-5%). There was limited evidence to show a dose–response effect of smoking. Conclusions This review reports a moderate association between maternal smoking and orofacial cleft but the overall quality of the conventional observational studies included was poor. There is a need for high quality and novel research strategies to further define the role of smoking in the etiology of cleft lip and palate.
Highlights
Cleft lip and/or palate (CL/P) is one of the most common craniofacial birth defects, occurring in approximately 1/700 births (Mossey et al, 2009)
There has been a large body of work to investigate the role of active maternal smoking in cleft lip only (CL)/P etiology, as shown by the 45 studies that met our inclusion criteria
This high volume of research should have provided a clear indication of the association between maternal smoking and CL/P, but the poor quality of studies overall has compromised the validity of the reported findings
Summary
Cleft lip and/or palate (CL/P) is one of the most common craniofacial birth defects, occurring in approximately 1/700 births (Mossey et al, 2009). It affects children and their families because of appearance and functional difficulties with speech, eating, social interaction, and child development. Seventy percent of children born with CL/P do not have an associated syndrome and the anomaly is believed to be caused by a complex pattern of inheritance with both genetic and environmental influences (Lebby et al, 2010). Maternal smoking is a modifiable environmental factor, which is considered a causal factor for CL/P in the 2014. Maternal smoking has attracted research interest because it is a common exposure and has been established as
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