Definition of Caput succedaneum:

Caput succedaneum is swelling of the scalp in a newborn. It is most often brought on by pressure from the uterus or vaginal wall during a head-first (vertex) delivery.

Causes, incidence, and risk factors:

A caput succedaneum is more likely to form during a prolonged or difficult delivery. This is especially true after the membranes have ruptured, because the amniotic sac is no longer providing a protective cushion for the baby's head. Vacuum extraction can also increase the chances of a caput succedaneum.

A caput succedaneum is sometimes identified by prenatal ultrasound even before labor or delivery begins. It has been found as early as 31 weeks of pregnancy. More often than not, this is associated with either premature rupture of the membranes or too little amniotic fluid (oligohydramnios). All other things being equal, the longer the membranes are intact, the less likely it is that a caput will form.