Does the placenta inhibit the passage of chromium and cobalt after metal-on-metal total hip arthroplasty?

Umbilical cord serum and corresponding maternal serum of 3 women with uncemented metal-on-metal total hip arthroplasties were analyzed for cobalt and chromium. The women were an average 3.8 (range, 2-5) years after hip surgery. At the time of delivery, the maternal chromium concentrations were 1.6 microg/l, 0.5 microg/l, and 0.9 microg/l, respectively, and the maternal cobalt concentration was 1 microg/l in the first woman and below the detection limit in the other 2 women. Cobalt and chromium concentrations of the 3 umbilical cord sera also were below the detection limit. This indicates that-with regard to the detection limit of our laboratory-we were unable to observe a passage of cobalt and chromium ions from metal-on-metal articulations across the placenta at the time of delivery.