Background Melasma is an acquired hypermelanosis of the face. There is little information on its prevalence during pregnancy in Iran. Objective To determine the prevalence and awareness of melasma during pregnancy at the Shahed University Hospitals of Tehran, Iran. Methods A cross-sectional study was carried out by clinical examination and questionnaire on 400 pregnant women. Results The prevalence of melasma was 15.8% [95% confidence interval (CI) 12.3-19.4]. Malar pattern was seen in 65.9% of cases, whereas 33.8% of the patients had a centrofacial pattern. No case with a mandibular pattern was found. Positive family history of melasma was present in 54.7% of the cases. There was a statistically significant relation between melasma and ethnicity, phototype and grade of parity. However, no significant relation was observed between melasma and use of sunscreens, history of thyroid or liver disorders, trimester of pregnancy or phenotype (eye and hair color). 11.3% of the patients declared that they have developed melasma after using OCP Oral Contraception. Patients had little awareness of the etiology of melasma. In fact, 68.8% of the patients had no knowledge of its etiology. The effective factors or etiologies for melasma were stated as: 14.5% pregnancy, 9.8% sun exposure, 4.9% liver disorders, 4.9% nutrition and 1.6% sex of newborn. Conclusions Our study confirms that melasma is common among pregnant women in Tehran, Iran. They had a low level of awareness of the etiology of melasma. There is a need for educational programs on the etiology and prevention of melasma in Iranian women.
