Case Report: High Chromium and Cobalt Levels in a Pregnant Patient with Bilateral Metal-on-Metal Hip Arthroplasties

Background Metal-on-metal bearings frequently are used in young patients leading to the concern that disseminated metals such as chromium (Cr) and cobalt (Co) as the main constituents could affect pregnancies.

Case Description We describe a 41-year-old patient with bilateral metal-on-metal hip arthroplasties, a recurrent pseudotumor, and extremely high blood levels (Cr 39 μg/L, Co 138 μg/L) at 12 gestational weeks. At different gestational weeks, maternal blood, aspirate of the pseudotumor, and amniotic fluid were analyzed for Cr and Co. Therapy with chelating agents was not recommended because the mother showed no symptoms of toxicity and the safety of chelating therapy during pregnancy is not established. At 38 weeks of gestation, a healthy male infant was delivered with elevated Cr and Co cord blood levels. At the age of 8 weeks, the infant’s Cr was comparable to the cord blood level, whereas the Co decreased considerably without treatment. At the age of 14 weeks, the infant’s development was seemingly uneventful and no signs of toxicity were obvious.

Literature Review Carcinogenic, mutagenic, and teratogenic potentials of these metals have been suggested. However, we found no published clinical observations in context with pregnancies of women with hip arthroplasties using metal-on-metal implants. To our knowledge, this is the first report of such high levels of Cr and Co in a human pregnancy.

Purposes and Clinical Relevance Although we cannot generalize from one case, the seemingly uneventful outcome of this pregnancy may reassure colleagues when counseling patients with high ion levels whether to carry a pregnancy to term.