Descriptive epidemiology of nonsyndromic cleft lip with or without cleft palate in Shanghai, China, from 1980 to 1989

Objective: The purpose of this study was to characterize nonsyndromic cleft lip with or without cleft palate (CL+/-CP) in an Asian population. Design: Birth prevalence was assessed in a large birth series in Shanghai, China. A 1:3 sex-age-hospital matched case-control design was used to asses s the effects of parental ages and pregnancy history on risk of CL+/-CP. Participants: Records of live births from 1980 to 1989 in 22 hospitals in S hanghai, China, were reviewed, comprising 541,504 consecutive births, which is by far the largest such Chinese sample ever investigated. The case-cont rol study included 528 (308 male, 220 female) nonsyndromic CL+/-CP cases an d 1563 (912 male, 651 female) controls. Results: From 1980 to 1989, the overall birth prevalence was 1.2 per 1000 l ive births with statistically significant seasonal variation (more CL+/-CP births in January to July). The overall male:female ratio was 1.40:1. For m ales, statistically significant associations were identified with maternal age for the most severe clefts (bilateral overall, and also bilateral CL+/- CP subgroup). For females, statistically significant association was shown for pregnancy age with birth order (overall and in most subgroups). Conclusions: The birth prevalence of CL+/-CP in this Asian population was s imilar to published Caucasian rates. The observed seasonal variation would be consistent with possible environmental factors. Significant associations with maternal age, pregnancy age, and birth order warrant additional study of pregnancy history in Asian CL+/-CP.