When a baby is described as “sunny side up,” it refers to the Occiput Posterior (OP) position during labor and delivery. While this is a variation of normal, it often leads to a more challenging labor experience. Many babies start in this orientation, but those who do not rotate on their own can cause difficulties for the birthing person.
Defining Occiput Posterior Position
The Occiput Posterior (OP) position occurs when the baby is head-down, but the back of their head (occiput) is positioned toward the mother’s spine (posterior side). This means the baby is facing the mother’s abdomen as they descend through the pelvis. The optimal position for birth is Occiput Anterior (OA), where the baby’s occiput faces the mother’s pubic bone, meaning the baby faces her spine.
In the OP position, the baby’s head is often less flexed, meaning the chin is lifted slightly away from the chest. This presents a larger diameter of the head to the narrowest parts of the pelvis compared to the smaller diameter presented in the OA position. Navigating the pelvis with this larger diameter often slows down progress. While up to 34% of babies may be in this position at the start of labor, only about 5% to 8% remain OP at the time of birth.
Factors Contributing to Occiput Posterior
Several factors can influence a baby’s position, leading to or maintaining the Occiput Posterior orientation. The shape of the mother’s pelvis can play a role, as certain shapes, like the anthropoid or platypelloid, offer less natural encouragement for the baby to rotate anteriorly. Other associated factors include a high maternal body mass index, advanced maternal age, and a birth weight greater than 4,000 grams.
The use of epidural anesthesia during labor is also linked to higher rates of persistent OP at delivery. This may be because the epidural relaxes the pelvic floor muscles, reducing the resistance needed to guide the baby’s head into the anterior position. An anterior placenta (positioned on the front wall of the uterus) is another factor that may encourage the baby to face the mother’s spine. Additionally, maternal behaviors, such as prolonged periods of reclining or sitting in semi-reclined positions, can influence the baby to settle into the posterior position.
Impact on Labor Progression and Duration
The OP position significantly affects labor dynamics, making the process less efficient and often longer. The less-flexed head position means the baby cannot apply optimal pressure to the cervix, slowing the progression of the first stage of labor. When the baby’s skull presses directly against the mother’s sacrum and surrounding nerves, it frequently causes intense, localized pain known as “back labor.”
The second stage of labor (the pushing phase) is often prolonged when the baby is in the OP position. This extended phase results from the baby needing to achieve a greater rotation, often a full 135 degrees, to exit the pelvis. If the baby fails to rotate, the larger head diameter increases the risk of medical interventions. Women with persistent OP face a higher risk of assisted vaginal delivery (vacuum extraction or forceps) or an emergency Cesarean section, with operative delivery rates ranging from 54% to 82%.
Strategies for Fetal Repositioning
Strategies for encouraging the baby to move out of the OP position focus on utilizing gravity and creating optimal space within the pelvis. During later pregnancy, adopting forward-leaning postures can help, such as spending time on hands and knees or sitting with the knees lower than the hips. Using a birth ball encourages an upright posture, which helps tilt the pelvis forward and create more space for rotation.
Once labor begins, active movement and changing positions become beneficial for rotation. Positions like the knee-chest position or side-lying on the side opposite the baby’s back can help shift the baby away from the sacrum. Studies show that semi-prone and knee-chest positions increase spontaneous rotation to the anterior position and can reduce the duration of the active phase of labor. If the baby remains OP and labor stalls, the healthcare provider may attempt a manual rotation, gently turning the baby’s head internally. When successful, this medical technique reduces the need for assisted delivery or C-section.