this study examined the determinants of blood lead ( bpb ) in 513 pregnant women in mexico city : 311 from public hospital prenatal clinics , representing primarily women of low socioeconomic status ( ses ) , and 202 from private hospitals , primarily women of high ses . overall , bpb levels ranged from 1.38 to 29 micrograms / dl , with geometric means of 6.7 and 11.12 micrograms / dl for women from private and public hospitals , respectively . 
 the crude geometric means difference obtained by t - test was 4.42 ( p < 0.001 ) . 
 bpb was measured from january 1994 to august 1995 and showed higher levels during fall and winter and lower levels during spring and summer . 
 the main bpb determinants were the use of lead - glazed ceramics in women from public hospitals and season of the year in women from private hospitals . 
 consumption of tortillas ( corn bread rich in calcium ) decreased bpb levels in the lower ses group , but the relationship was not statistically significant ( p > 0.05 ) . 
 consumption of milk products significantly ( p < 0.05 ) reduced bpb levels in the higher ses group . in 112 women 
 whose diets were deficient in calcium , taking calcium supplements lowered their blood lead levels about 7 micrograms / dl . 
 a predictive model fitted to these data , using the strongest predictors plus gestational age , showed a difference of 14 micrograms / dl between the best and worst scenarios in women from public hospitals . 
 avoiding use of lead - glazed ceramics , consuming diets rich in calcium , and , if needed , taking calcium supplements , would be expected to result in substantial lowering of bpb , especially in pregnant women of low socioeconomic status.imagesfigure 1.figure 2 .