Environmental factors in the first trimester and risk of oral-facial clefts in the offspring.

The averaged incidences of nonsyndromal/isolated cleft lip (CL), cleft palate (CP), and cleft lip with cleft palate (CLCP) by each month-of-conception, and managed in our hospital in from 2002 to 2009 were correlated with the reported levels of sunshine, ultraviolet radiation, and ambient nitrogen oxides (nitrogen oxide, nitrogen monoxide, and nitrogen dioxide), sulfur dioxide, and ozone, at the month of, and then at 4 and 8 weeks after, conception. There were 25, 12, and 22 cases each of CL, CP, and CLCP, respectively, totaling 59 cases (1.21 of 1000 births). On regression analysis, sunshine correlated inversely with the isolated CL at (P = .009) 4 weeks (P = .005) and 8 weeks (P = .008) postconception, and with CP (P = .009) and CLCP (P < .001) at 8 weeks postconception, while NOx correlated inversely with CL (P = .018) and NO with CLCP (P = .031), at 8 weeks postconception. Our results suggested that the interaction between sunshine and nitrogen oxides with other factors results in the reported seasonal variation in the incidence of isolated oral-facial clefts.