To search for the type of orofacial cleft responsible for the significant decrease in the total monthly number of new-born boys observed in April (Fig. 3b), we separately plotted the curves of MDN for boys with CL, CLP or CP (Fig. 4a, b, c), and the total monthly numbers of new-borns for 37 years (Table 1) were evaluated by Fisher’s exact test [31]. The gene discussed is CP; the disease is orofacial cleft.