Association of maternal lead exposure with the risk of preterm: a meta-analysis.

Background: The relationship between maternal lead level and risk of preterm birth (PTB) remained controversial. Therefore, herein we performed this meta-analysis to investigate the association of maternal blood, urine and cord blood lead level with the risk of PTB using observational studies.
Methods: A systematic search was conducted in PubMed, EMBASE and Ovid Medline databases from inception to August 2019, and sixteen studies with 65600 participants investigating the association between maternal lead level and PTB were included in our meta-analysis. Odds ratios (ORs) and 95% confidence intervals (95% CI) were calculated for the highest versus lowest lead level by random-effects model.
Results: Overall, the pooled OR of all included articles for the highest versus lowest PTB score was 1.29 (95% CI = 1.14-1.46; I2 = 80.4%, p  < .001), and the results revealed a direct and significant relationship between second and third trimester blood lead level (BLL) and PTB (OR 2nd trimester= 1.61, 95% CI = 1.08-2.40, OR 3rd trimester= 1.57, 95% CI = 1.11-2.23).
Conclusion: Results of this meta-analysis showed that maternal BLL is directly associated with the risk of PTB.