Fetal brain development supported by placenta

Researchers recently found evidence that the placenta, the organ that connects the fetus to the uterine wall of its mother, contributes to fetal brain development during pregnancy. Experiments in mice showed that the placenta functions as a source of serotonin during a key period, contributing to the wiring of brain circuits. These findings could potentially explain how brain disorders such as schizophrenia develop.

Pat Levitt, director of the Zilkha Neurogenetic Institute at the University of Southern California’s Keck School of Medicine, says that the placenta does more than transport nutrients from a mother to her fetus. Instead, the placenta produces hormones whose effects can influence the brain of the fetus at a particular period in development. Serotonin, which affects the forebrain, can have a lasting impact on the fetus.

According to Levitt, the forebrain contains circuits that are disrupted in autism, schizophrenia, bipolar disorder, anxiety and depression. Knowing how serotonin is supplied to the forebrain of a developing fetus could be important in understanding these conditions. The team’s experiments in mice showed that serotonin was not initially produced in the fetus itself, implying that it came from the mother.

While mothers do produce serotonin, Levitt’s experiments showed that serotonin from a mother cannot reach the fetus because serotonin is unable to cross the placenta. This led the team to consider the possibility that the placenta itself is the source of serotonin. Experiments on mice confirmed that the placenta produces serotonin during a specific period in early fetal development and that the human placenta also has the potential to make serotonin.

Other research suggests that serotonin is not the only important brain-signaling chemical made by the placenta. Levitt says that the placenta can also produce dopamine, a chemical that plays an important role in brain development and mental illness. These findings can potentially be used to determine children’s risk of developing autism or mental illness as well as lead to a better understanding of what happens to the brain during pregnancy.