The posterior position is medically known as the occiput posterior position. It is the commonest fetal malposition and important due to its associations with abnormalities in labor that can cause consequences to both mother and child. Before labor begins, as many as 15% to 20% of babies are in the posterior position while only 5% are still in this position during delivery. This happens as most babies naturally rotate to the anterior position once labor begins. In some cases, the posterior position during delivery is a result from a malrotation. This position can cause issues as the passage is unfavorable for the baby to pass through. The progress of labor should be monitored. Here is a diagram that shows what an occiput posterior position looks like compared to the normal (occiput anterior) position.
Having a Posterior Baby
As previously established, the posterior position occurs when the back of the baby’s head is pressing against the back of the mother. When this occurs, the baby’s back is straight along the mother’s spine leading to the baby’s chin being pushed up. This causes the baby’s head to appear larger compared to the anterior position (face down) as the posterior hear circumference is bigger than the anterior head circumference. There are our types of posterior positions:
o Direct occiput posterior position – This occurs when the baby is facing straight forward.
o Right occiput transverse – This is a common position where the baby has a higher chance to rotate to the posterior position compared to the anterior position.
o Right occiput posterior – This occurs when the baby’s back is extended causing the chin to be pushed up and usually happens in first time mothers.
o Left occiput posterior – this occurs when the baby’s back is at the left side and can lead to flexing of the back and tucking of chin.
Learn more about your baby’s position through belly mapping!
Reasons for the Occiput Posterior Position
Some of the reasons your baby may be in a posterior position are:
a) Shape of Your Pelvis
Depending on the shape of your pelvis, the baby may be in a posterior position. For example, android and anthropoid shaped pelvises can cause babies to be in the posterior position. Android shaped pelvises are heart shaped and can lead to posterior position of the baby due to the narrower front. Anthropoid shaped pelvises have an oval shaped inlet, narrow pelvic cavity, and large antero-posterior diameter. Click here to look at different pelvic shapes!
When the mother has kyphosis or excessive curvature of the spinal cord, the fetal back can fit itself into the curve leading to a posterior position.
Women who sit on a computer chair or couch for prolonged periods of time can cause the tilting of the pelvis to the back. This causes the baby’s head to rest on the pelvis, increasing pressure on the spine.
Risk Factors for Occiput Posterior Position
There have been several risk factors that have been associated with the posterior position in babies. An occiput posterior position of the babies can complicate labor as it prolongs the process. Some of these include:
o Maternal age is more than 35 years old
o First pregnancy (nulliparity)
o History of occiput posterior delivery
o Pelvic outlet capacity is decreased
o Mothers of the African American race
o Babies whose weight is more than 4000 grams
o Babies whose gestational age is more than 41 weeks
o Mothers who opt for epidural anesthesia
o Mothers who go through artificial rupture of membranes
How the Occiput Posterior Position Affects Labor
In most cases, babies in the occiput posterior position rotate to the occiput anterior position once labor starts. However, some babies stay in the posterior position. While some babies are able to be delivered without any prolongation or complication of labor, some cases where the baby is unable to turn can lead to a caesarean section. Babies that are delivered in the occiput posterior position usually require assistance with instruments such as vacuum, forceps, and sometimes caesarean section.
Complications of Occiput Posterior Labor
Some of the complications in the delivery of a posterior baby are:
o Postpartum hemorrhage – This occurs when there is blood loss of more than 500ml.
o Risk of infections
o Requirements of using instruments to assist delivery such as forceps and vacuum. This can lead to third and fourth degree tears in the perineum.
o Prolonged first and second stage of labor with associated backache.
o Induction may be required to start the labor
o There is risk of chorioamnionitis, which is the inflammation of fetal membranes because of infection.
o There is a risk of endometritis, which is the inflammation of the lining of the uterus due to bacterial infection.
o Babies delivered in the occiput posterior position are more likely to have a low APGAR score of less than 7.
o Other complications that may affect the baby includes birth trauma, neonatal intensive care unit (NICU) admissions, meconium stained amniotic fluid, and longer stay at the hospital.
The posterior position of the baby is usually confirmed using an ultrasound scan. Once the fetal heart rate is deemed to be reassuring, management can include:
o Manual rotation of the baby to the occiput anterior position
This is usually performed during the second stage of the labor when the cervix is fully dilated. Your doctor will insert his or her hand with the palm facing upwards. The fetal head is then rotated to the occiput anterior position and held in place to prevent it from reverting back to the posterior position while the mother is encouraged to push.
o Operative vaginal delivery
This is performed if there is enough room between the occiput of the baby and sacrum allowing the baby to turn. Vacuum extractor or forceps can be used to assist in delivery.
o Caesarean section
This is a surgery performed when the methods above cannot help in the delivery of the baby.
Prevention of Occiput Posterior Position
Some of the ways that may help in the prevention of the posterior position of your baby are:
Some of the exercises include walking, swimming, and pelvic rocking.
: In this phase, try rocking your pelvis for 10 times in two to five sets a day. This can be done by getting down on fours and leaning forward as much as you comfortably can. You can also take advantage of hot and cold packs and put these on your belly or back as babies will turn towards warmth.
– End of first stage of labor
: In this phase, f your baby is starting to move towards the anterior position, squatting can relax the pelvic floor muscles allowing more room for the baby to rotate.
: In this stage, timing the double hip squeeze with your contractions can help spread the pelvis, allowing more room for the baby to turn.
Some techniques and therapies such as chiropractic and acupuncture may be able to fix the alignment of your body which can help the baby to turn to the anterior position.
Try to avoid positions where you recline or sit with your pelvis tilted. To maintain good posture, try using a birth ball. Try sleeping towards the left side by keeping your left leg straight and right one at 90 degrees while being supported by pillows between your legs.
Here is a link that has more detail about preventing posterior labor.