Background: It is well known the adverse effect of mercury exposure on pregnant women and newborns. Interactions between environmental factors and individual genetic susceptibility have been identified, particularly polymorphisms of codifying genes for the Glutathione S-transferase family (GSTs). Herein, we report a case series of patients with high Hg levels in biosamples. Case Series: Fourteen cases with high Hg levels were identified. Non-occupational or home exposure risk factors were identified. All mothers reported fish consumption during pregnancy. Almost 60% of the individuals were null for either one GSTs gene. To date, in the subsequent mother-child pairs toxicology controls no signs or symptoms of poisoning were identified and most of the mercury levels decreased and are below the accepted limit. Discussion: In this case series we found some similarities with the literature; among them, the relation of Hg ratio in maternal blood and umbilical cord, a possible exposure factor is the consumption of fish during pregnancy and, the high levels of Hg may be related with susceptibility biomarkers such as GSTs gene polymorphisms. This case series highlights the need to develop studies that evaluate the interactions between environmental factors and individual genetic susceptibility. Additionally, the importance of evaluating which Colombian fish species present the highest levels of Hg.