Posterior asynclitism refers to the fetal head position during childbirth, where the back of the baby's head is tilted towards the mother's spine. This can cause complications and prolonged labor, increasing the need for intervention. There are several synonyms for this condition, including occiput posterior, OP position, and sunny-side up position. When the baby is in the posterior position, it can make the delivery more challenging, as the baby's head doesn't fit perfectly into the birth canal. Healthcare providers may try various techniques to help rotate the baby into the correct position for a smoother delivery.