Caput succedaneum is diffuse swelling due to accumulation of interstitial fluid in the soft tissues of the scalp in a neonate caused by pressure from the uterus or vaginal wall during vertex delivery. In other words, the baby's scalp gets swollen from being squished in the birth canal. It is caused by mechanical trauma and may occur on any part of the scalp. It can cross the midline (unlike a cephalhematoma) and is a common phenomenon that resolves in a few days without treatment.