Background: Exposure to toxic metals in the prenatal period may have a negative impact on birth weight and placental weight (BW/PW). Low birth weight is an important etiological factor for chronic diseases in advanced ages. The levels of essential elements are also important for healthy progress of pregnancy, but abnormal levels may be harmful, such as excessive zinc (Zn) in the body increases BW/PW. Placental tissue directly provides information to clinician about maternal and foetal exposure. Aims: To investigate the impact of cadmium (Cd), lead (Pb) and zinc (Zn) levels on birth weight. Methods: This study involved the measurement of metal levels in 150 participants by inductively coupled plasma mass spectrometry (ICP-MS). Results: There were positive significant correlations with BW/PW ratio and gestational age (r=0.205, p = 0.012), number of births (r=0.182, p = 0.025), birth weight (r=0.505, p<0.001), and birth size (r=0.296, p < 0.001). Maternal blood Cd levels positively correlated with placental weight (r=0.256, p=0.002) and negatively correlated with BW/PW ratio (r=-0.188 p = 0.021). Foetal placenta Pb levels were positively correlated with BW/PW ratio (r=0.198, p=0.015). Differences between maternal and foetal placenta Zn levels were found to be statistically significant (23.90 ± 3.26 and 25.50 ± 4.69, respectively, p < 0.001). Furthermore, Zn maternal levels of healthy births were found to be statistically different (p = 0.014) when compared with pregnancies with curettages and stillbirths. Conclusion: The findings are consistent with the hypothesis that increased Pb and Cd levels in pregnancy results in a low birth weight and these effects cannot be reversed by Zn, the levels of which are positive related with healthy births. Environmental heavy metal exposure in pregnancy should be routinely examined for baby health.

Keywords: Prenatal Care; Stillbirth; Heavy Metals; Zinc supplementation; Birth Weight.