Epidemiology of oral clefts in a large South American sample.

A total of 849,381 newborn children were examined during the years 1967 to 1981, in 56 hospitals of eight countries, in the Latin American Collaborative Study of Congenital Malformations (ECLAMC). Of these, 741 had a cleft lip with or without a cleft palate (CL +/- P), yielding a global prevalence of 0.87 per thousand, and 115 had cleft palate (CP) only (frequency: 0.13 per thousand). CP frequencies by country and by year were essentially homogeneous, but those for CL +/- P showed heterogeneity by country (but no temporal trends). Patients thus ascertained, with matched, appropriate controls, have been subjected to a detailed epidemiologic study. For CP, only the sex ratio deviated from the control values; but for CL +/- P the marked divergence in sex ratio was accompanied by differences in the two series on the frequency of twin births, birth weight, neonatal survival, birth order, medicine use, and occurrence of acute or chronic illnesses during the first trimester of pregnancy. Lack of agreement of these results with previous data may be due to different types of patient ascertainment, sample sizes, and methods of analysis.