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Impact of alopecia areata on subsequent pregnancy rate: A retrospective cohort study

Alopecia areata (AA) is considered to be a cell-mediated autoimmune disease that often results in unpredictable hair loss and associated with other autoimmune diseases, such as thyroid disease and lupus erythematosus. To date, it is known that many autoimmune diseases may effect pregnancy outcomes. However, there has been no previous study of how alopecia areata affects subsequent chance of pregnancy. Therefore, we performed a retrospective cohort study to investigate the effect of alopecia areata on pregnancy rate using data from the National Health Insurance Service-National Sample Cohort (NHIS-NSC). The NHIS-NSC has been proven to be a useful research tool and has been used in previous studies. During the period January 2004 to December 2013, we identified 1,382 fertile (20 to 39 years old) female patients with alopecia areata who had at least two principal diagnostic codes (International Classification of Diseases, Tenth Revision: ICD-10) for alopecia areata (L63 and its all sub-classification codes) assigned only by dermatologists from a representative sample cohort of 1 125 691 (Fig. 1). Among the alopecia areata patients, we defined patients with severe alopecia areata (N = 35) as those having a diagnostic code for alopecia totalis, alopecia universalis or ophiasis; others were defined as mild alopecia areata (N = 1347). We also defined patients with long-standing alopecia areata (N = 160) as those having 12 or more diagnostic codes for alopecia areata over a minimum of one year; others were defined as episodic alopecia areata (N = 1222). To define a control group (N = 6910), we randomly selected five index date-, age group-, genderand income level-matched individuals for each alopecia areata case in the NHIS-NSC who had never been assigned diagnostic codes for alopecia areata. Subsequent pregnancies were investigated using corresponding ICD-10 codes (Z32.1, Z33, Z34, Z35, Z36 and O30). Result of the chi-square test found the prevalence of vitiligo and ovarian dysfunction (ICD-10 codes; E28 and its all