“…Its effects on birth outcomes, however, particularly at moderate exposures, are not well understood and in this regard Cd has received far less research attention than its near neighbours in the periodic table, lead and mercury, The placenta is thought to be at least a partial barrier to Cd transfer to the fetus,5, 6 but determination of ratios of Cd in cord blood : maternal blood have left this in doubt (ratios ranging from 0.247 to 1.08,8 with others finding intermediate values9, 10). Studies with moderate maternal blood cadmium levels (B‐Cd; below a suggested reference value of 1 μg/L11) and adjustment for smoking have generally found no associations with birthweight, birth length, head circumference or preterm delivery,8, 12, 13 but other studies have found negative associations particularly with birthweight14, 15, 16 (Table S1). Even where exposure levels are higher and effects could potentially be more evident, again some studies have found no associations with birth outcomes,10, 17 while others have found adverse associations 18.…”