Heavy Metals in Umbilical Cord Blood: Effects on Epigenetics and Child Development

Abstract

Heavy metals like arsenic, mercury, cadmium, and lead are harmful pollutants that can change how our genes are regulated without altering the DNA sequence, specifically through a process called DNA methylation (DNAm) at 5-methylcytosine, an epigenetic mark that we will focus on in this review. These changes in DNAm are most sensitive during pregnancy, a critical time for development when these modifications can affect how traits are expressed. Historically, most research on these environmental effects has focused on adults, but now there is more emphasis on studying the impacts during early development and childhood. The placenta acts as a protective barrier between the mother and the baby, and by examining it, scientists can identify changes in key genes that might affect long-term health. This review looks at how exposure to heavy metals during pregnancy can cause changes in the gene regulation by DNAm in newborns, as seen in their umbilical cord blood. These changes reflect the baby's genetic state during pregnancy and can be influenced by the mother's environment and genetics, as well as the baby's own genetics.

Keywords: developmental toxicology; heavy metals; placenta; umbilical cord blood.

Figure 1

A growing fetus inside the mother’s uterus showing the umbilical cord and placenta. The structure of the human placenta showing the direction of maternal–fetal transfer. The fetal side of the placenta comprises umbilical arteries (which deliver nutrients and oxygen to the growing fetus) and umbilical veins (which transport back waste products and CO₂ from the fetus to the maternal circulation). The maternal side consists of a basal plate with maternal vessels. The middle portion of the placenta consists of chorionic villi.

Figure 2

Heavy metal transition from mother to fetus. Heavy metals are released in the environment from several sources, such as mining, oil refineries, combustion by-products, fertilizers, and pesticides. Heavy metals can get easily transmitted via the maternal circulation and affect the growing fetus.