'No one knows what they are': Researchers discover new type of cell that's seen only during pregnancy

Scientists have created a comprehensive map of placental and uterine tissue throughout pregnancy, analyzing 1.2 million cells to understand how these organs develop and function. They discovered a previously unknown cell type that appears only during pregnancy and acts as a "speed bump" to regulate fetal cell invasion into the uterus. These cells carry receptors sensitive to cannabinoids, potentially explaining why cannabis use during pregnancy increases risks of preterm birth and low birth weight by disrupting placental blood flow.