Risk Factors Of Microtia:Systemic Review And Meta—Analysis

Background:The pathogenesis of microtia is still unclear. Various risk factors have been studied but inconclusive. We conducted the first ever systemic review and meta-analysis to look for the association between microtia and various environmental risk factors.Methods:Relevant Case-control studies published between 2000-01 to 2014-10 were identified through systemic search in PubMed and EMBASE.Reference list from relevant review articles were also searched. Studied were included if they meet our selection criteria. Of 1706 potential articles,12 were included in the systemic review and 8 in the meta-analysis.Results:Risk factors which showed Significant positive association was microtia were:Flu-like symptoms during Pregnancy (OR=2.15; 95% CI=1.36,3.41, P=0.001); Multiple Gestation (OR=1.55; 95% CI=1.05,2.29,P=0.03); Gestational Diabetes (OR=1.48; 95% CI=1.04,2.10,P=0.03). Risk factors which showed positive association but statistically insignificant were:Threatened abortion (OR=1.22; 95% CI=0.69,2.15,P=0.50); Smoking during Pregnancy (OR=1.05; 95% CI=0.63,1.77, P=0.84); Alcohol during Pregnancy (OR=1.08; 95% CI=0.65,1.80 P=0.77); Urinary Tract infection (OR=1.04; 95% CI=0.59,1.84, P=0.89); Essential Hypertension (OR=1.04; 95% CI=0.74,1.47,P=0.82); Maternal Diabetes (OR=3.98; 95% CI=0.72,21.96, P=0.11); Respiratory Tract infection (OR=1.26,95% CI=0.84,1.88, P=0.26); Chronic Disease during Pregnancy(OR=1.29,95% CI=0.99,1.69, P=0.06); Severe Nausea/Vomiting (OR=1.16; 95% CI=0.66,2.04,P=0.61); NSAIDs during Pregnancy (OR=1.17,95%CI=0.61,2.22, P=0.64); Anti-hypertensive during Pregnancy (OR=1.84,95% CI=0.94,3.62,P=0.08); Illegal drug during Pregnancy (OR=1.69; 95% CI=0.65,4.39,P=0.28). Reduced risk for microtia was found with these factors:Folic acid (OR=0.55; 95% CI=0.33,0.92, P=0.02); Advanced Maternal Age (OR=0.94; 95% CI=0.79,1.11, P=0.45); Ampicillin during Pregnancy (OR=0.80,95% Cl=0.50,128, P=0.35); Metronidazole during Pregnancy (OR=0.77,95% CI=0.40,1.48 P=0.44).Conclusion:Our study showed that flu-like symptoms, multiple gestation and gestational diabetes are significant risk factors for microtia; whereas folic acid consumption during pregnancy is shown to be a protective factor. Studies on risk factors for microtia are still very limited to establish the definitive risk factors. Further large scale and multicentre studies are needed to clarify the role of key risk factors for the development of microtia.