Prenatal blood lead levels and Birth Weight: a Meta-analysis study

Purpose Lead, a known toxic metal, causes several adverse reproductive effects, including low birth weight. Fortunately, the exposure level has sharply decreased during the recent decades, but a definitive safe level did not introduce for pregnant women yet. The current meta-analysis study aimed to conduct a quantitative estimation of maternal and umbilical cord blood lead effects on birth weight. Methods Two researchers have independently searched the scientific literature for retrieving related studies using the PRISMA criteria for data extraction. Twenty-one full-text articles were selected from primary 5006 titles, limited by the English language and published between 1991 and 2020 on humans. Results The pooled mean of maternal and umbilical cord blood lead levels were 6.85 mu g/dL (95% CI: 3.36-10.34) and 5.41 mu g/dL (95%CI: 3.43-7.40), respectively. The correlation coefficient analysis showed a significant inverse association between the mean maternal blood lead level and birth weight, which was confirmed by Fisher Z-Transformation analysis (-0.374, 95% CI: -0.382, -0.365, p < 0.01). In addition, a significantly lower birth weight (delta: 229 gr, p < 0.05) was found in the relatively high level of maternal blood lead than in low-level exposure (> 5 mu g/dL vs. <= 5 mu g/dL, respectively). Conclusion In short, the present study findings suggest an increasing maternal blood lead levels could be a potential risk factor for reducing birth weight. Thus, pregnant women should avoid lead exposure, as much as possible.