HETEROGENEOUS RATES FOR BIRTH-DEFECTS IN LATIN-AMERICA - HINTS ON CAUSALITY

The aim of this work was to disclose risk factors associated with birt h defects which were heterogeneously distributed in the different geog raphic regions sampled by the Latin American Collaborative Study of Co ngenital Malformations (ECLAMC). The material included 2,159,065 hospi tal births, delivered in the 1963-1989 period in 24 geographic regions of Latin America. Birth defect types with 50 case-control pairs or mo re were analyzed. A risk factor was defined as that available variable with differential geographic rates, correlated with those of a given birth defect type. Identified factors were tested by case-control mult ivariate logistic regression to confirm their role in the occurrence o f the defect. Altitude and maternal acute illness during first trimest er of pregnancy, named influenza, were risk factors for microtia. Pren atal drug exposure, mainly sex hormones, were connected with the occur rence of hypospadias in low frequency areas, while Native ancestry was a ''protective'' factor in the same regions. Acute (influenza), and c hronic (epilepsy and syphilis) maternal illness during first trimester of pregnancy and gravidity higher than four were risk factors for cle ft lip. The independence of these variables from maternal age suggeste d that low maternal socioeconomic level could explain the high birth d efect order and, perhaps, syphilis in mothers. Postaxial polydactyly w as associated with parental consanguinity, as well as Afro-American an cestry, suggesting genetic heterogeneity. (C) 1996 Wiley-Liss, Inc.