CLASSIFICATION AND BIRTH PREVALENCE OF OROFACIAL CLEFTS

To determine the proportion and birth prevalence of ''typical'' orofac ial clefts (cleft lip (CL), cleft palate (CP), cleft lip and palate (C LP)) and ''atypical'' clefts (median, transversal, or oblique facial c lefts) and the conditions in which they occur, we analyzed a populatio n-based sample of 4,433 cases ascertained from 2,509,881 California bi rths. We classified cases into: isolated cleft anomalies, sequences of the primary defect, chromosomal aberrations, monogenic syndromes, res ults of known teratogens, associations, multiple congenital anomaly (M CA) of unknown etiology, or conjoined twins. The birth prevalence of i solated CL+/-P was 0.77 per 1,000 births (CL 0.29/1,000, CLP 0.48/1,00 0) and of isolated CP, 0.31 per 1,000 births. Non-Hispanic Whites had the greatest prevalence of isolated clefts, Asians slightly lower prev alences, and Blacks the lowest. Asians had the lowest prevalence of Ro bin sequence and non-Hispanic Whites the highest, twice that of Hispan ics. Hispanics, followed by Asians, had the highest prevalence of CL+/ -P with MCA; non-Hispanic Whites had the lowest. Asians had the lowest prevalence of CP; in Whites and Hispanics it was almost twice as high . Blacks had the highest CL:CLP ratio, followed by non-Hispanic Whites and Asians; Hispanics had the lowest. Isolated anomalies constituted 61.67% of clefts. In the total sample there were 3.9% sequences, 8.79% chromosomal aberrations, 6.02% monogenic syndromes, 0.2% known terato gens, 0.79% associations, 18.55% MCA of unknown etiology, and 0.1% in conjoined twins. This study supports evaluation of each child on a ''c ase'' level, and provides a framework for genetic counseling and other studies focused on causes and prevention of these serious anomalies. (C) 1998 Wiley-Liss, Inc.