Blood lead at currently acceptable levels may cause preterm labour.

Objectives: Although occupational and environmental exposures to lead have been dramatically reduced in recent decades, adverse pregnancy outcomes have been observed at 'acceptable' levels of blood lead concentrations (≤ 10 μg/dl).

Methodology: Blood samples were collected from 348 singleton pregnant women, aged 16-35 years, during the first trimester of pregnancy (8-12 weeks) for lead measurement by inductively coupled plasma-mass spectrometry. Subjects were followed up and divided into two groups (preterm and full-term deliveries) according to duration of gestation.

Results: The average (range) and geometric means of blood lead levels were 3.8 (1.0-20.5) and 3.5 μg/dl, respectively. Blood lead level was significantly (p<0.05) higher in mothers who delivered preterm babies than in those who delivered full-term babies (mean±SD: 4.46±1.86 and 3.43±1.22 μg/dl, respectively). Logistic regression analysis demonstrated that a 1 unit increase in blood lead levels led to an increased risk of preterm birth (OR 1.41, 95% CI 1.08 to 1.84).

Conclusion: Adverse pregnancy outcomes may occur at blood lead concentrations below the current acceptable level.