[Lead blood levels in mothers and newborn infants covered by the Mexican Institute of Social Security].
To establish the relation between maternal blood lead (MBL) and umbilical cord blood lead (CBL) levels during delivery, and to determine the major predictors for MBL in women covered by the Mexican Institute of Social Security (MISS), in Mexico City. From 1991 to 1993, a cross-sectional study was conducted in four MISS hospitals, among normal pregnant women who volunteered to participate. Blood samples were taken from women and from the umbilical cord during delivery. Statistical analysis consisted of descriptive statistics and simple and multiple linear regression. A total of 1,404 mother-newborn pairs were studied. Mean maternal age was 25 years. MBL average was 10.7 +/- 6.5 micrograms/dl; no significant differences were found by hospital, age, or marital status. Mean CBL was 10.4 +/- 6.2 micrograms/dl. A log unit increase in MBL corresponded to a log increase of 0.62 in CBL (p < 0.01). Pearson's correlation was 0.61 (p < 0.01). The main predictors of MBL were: Use of lead-glazed ceramic (positively associated) and milk and orange juice intake (negatively associated). Forty-seven percent of mothers and 50 percent of the newborn babies had values higher than 10 micrograms/dl, and 578 of them had blood lead levels higher than their mothers. Further studies should be carried out in order to identify necessary interventions.