Recent studies have shown that the protein MIA (melanoma inhibitory activity) is a potent serum marker for malignant melanoma. MIA is expressed in chondrocytes at high levels, and might potentially be elevated during periods of growth in childhood. Therefore, we evaluated MIA serum levels in pregnant women and in growing children. We found that no significant enhancement of MIA serum levels was apparent until 38 weeks of pregnancy. Starting at 38 weeks, a significant increase was noted. The study further revealed that children and teenagers also have increased MIA serum levels. However, from the age of 17 years MIA serum levels are not different from those in healthy adults. In summary, MIA can be used as a serum marker for melanoma in adults starting at the age of 17 years. In pregnant women (> 38th week), children, and teenagers MIA should not be used in serum diagnostics for malignant melanoma until larger studies have been performed to generate cut-off levels for each group.