The term “sunny side up” refers to the occiput posterior (OP) fetal position. This means the baby is head-down, but the back of the skull presses against the mother’s spine, causing the baby to face forward toward the abdomen. This orientation is a frequent concern during labor because it is often associated with a more challenging and intensely painful birth experience.
Understanding Occiput Posterior Presentation
Fetal positioning is categorized by the relationship between the baby’s skull and the mother’s pelvis. The most favorable position for a vaginal birth is the occiput anterior (OA) presentation, where the baby faces the mother’s spine, with the back of the head toward the front of the pelvis. When a baby is in the OA position, the smallest part of the head leads the way, allowing for an easier passage through the curved birth canal.
The occiput posterior (OP) position is the reverse, where the occiput is positioned toward the mother’s back, making the face look upward. This orientation means the baby’s head does not tuck or flex as easily, presenting a larger diameter to the pelvis. About 20% of babies may be in this position at the start of labor, though most rotate spontaneously before delivery.
Why This Position Increases Discomfort
The primary reason an OP presentation is associated with increased discomfort is the direct pressure exerted on the mother’s sacrum and spinal nerves. This intense and localized pain is commonly referred to as “back labor”. When the baby is in the posterior position, the hard, bony part of the skull’s occiput pushes directly against the mother’s tailbone and lower spine during contractions.
This pressure irritates the nerves in the lower back, causing intense pain that is often concentrated in the lumbar region, unlike the more common abdominal discomfort of typical labor. For women experiencing back labor, the pain may be constant, even between contractions, and can worsen significantly when a contraction peaks. The severity of the pain is directly related to the mechanical pressure from the baby’s head.
The continuous, grinding sensation caused by the occiput pressing on the sacrum can be exhausting for the mother. While some women experience back labor even with an anterior baby, the OP position is the most frequent cause. The discomfort often subsides once the baby rotates, but the sustained pressure makes the experience significantly more challenging.
Impact on Labor Progression and Delivery
The less-than-optimal alignment of the baby’s head in the OP position often has consequences for the duration and progress of labor. Because the head does not flex efficiently to fit the pelvic curve, the baby may have difficulty descending, which can lead to a prolonged labor. This slower progression is often described as a “failure to progress” in the medical setting.
If the baby remains in the posterior position, the likelihood of needing medical interventions increases substantially. The OP position is associated with higher rates of assisted delivery, such as the use of forceps or a vacuum extractor, to help turn the baby and facilitate birth. The risk of a Cesarean section is also elevated when the baby fails to rotate or descend, especially if the labor is prolonged.
Up to 75% of babies who start in the posterior position will rotate spontaneously during labor. However, the 5% to 8% that remain OP at delivery require careful management. The mechanical challenges mean the baby’s head must travel a longer, more difficult path, making the process more taxing for both mother and baby.
Strategies for Management and Rotation
While the OP position presents challenges, practical and medical strategies exist to encourage rotation and manage discomfort. During late pregnancy and early labor, specific maternal positioning techniques leverage gravity to create more space in the pelvis. Common recommendations include spending time on hands and knees, leaning forward over a birth ball, or performing gentle pelvic tilts.
These forward-leaning postures aim to shift the baby’s weight away from the spine, encouraging the heavier back of the head to rotate toward the mother’s abdomen. During labor, continuous movement, such as walking, swaying, or using a side-lying position, can also facilitate spontaneous turning.
If the baby remains posterior, practitioners may employ medical interventions. An epidural can sometimes relax the pelvic floor muscles, providing space for the baby to rotate. In the second stage of labor, a healthcare provider may attempt a manual rotation, gently turning the baby’s head into the anterior position. This procedure is a safe option that can significantly reduce the need for an operative delivery.