An anterior lip during labor is a temporary situation where a small portion of the cervix has not fully retracted or dilated, remaining in the birth canal. Typically, this occurs when the cervix is almost completely open, but a small rim remains in front of the baby’s head. It is a common variation in labor progression.
What is an Anterior Lip?
The anterior lip is the front-most part of the cervix, which is the lower, narrow portion of the uterus. During labor, the cervix thins and widens to allow the baby to pass through the birth canal. This process, called effacement and dilation, involves the muscular fibers of the uterus pulling the cervix up and around the baby’s head.
When this front portion of the cervix gets caught between the baby’s head and the pubic bone, it forms an anterior lip. This remaining cervical tissue can sometimes become swollen due to the pressure exerted by the baby’s head. Its presence is typically identified through a vaginal examination by a healthcare provider.
Why an Anterior Lip Forms
An anterior lip can form for several reasons related to the mechanics of labor and the baby’s position. One common factor is the way the cervix dilates, which often occurs in an elliptical rather than a perfectly circular fashion; the front portion is frequently the last to retract fully. The baby’s position in the pelvis also plays a significant role. If the baby is not optimally positioned, such as being in an occiput posterior (OP) position where the back of the baby’s head is towards the mother’s back, it can create uneven pressure on the cervix, hindering the complete retraction of the anterior cervical tissue. Additionally, an individual’s unique anatomy, or sometimes pushing before the cervix is fully dilated, can contribute to its formation.
How it Affects Labor
The presence of an anterior lip can impact the progression of labor, particularly during the pushing phase. It can obstruct the baby’s head from descending fully into the birth canal, even if the rest of the cervix is completely dilated. This can lead to a stall in labor progress, where the birthing person may feel a strong urge to push but makes little advancement.
Pushing against an anterior lip can cause it to become more swollen, potentially prolonging the pushing stage. This can result in increased maternal exhaustion and a feeling of frustration. While generally not a dangerous situation, it can make labor more challenging and extended.
Addressing an Anterior Lip
Several strategies can help resolve an anterior lip and facilitate labor progress.
Positional Changes
Changing the birthing person’s position can help shift the baby and allow the cervix to retract. Positions such as side-lying, hands and knees, or squatting can be beneficial. Elevating the hips or using a semi-reclining position can also help take pressure off the cervix.
Rest and Waiting
Allowing a period of rest and waiting can be effective, often referred to as “tincture of time.” If the birthing person is not experiencing an overwhelming urge to push, pausing and resting can give the cervix time to recede naturally. This approach helps conserve maternal energy and allows the body to continue the process without forced intervention.
Directed Pushing and Manual Reduction
Healthcare providers may also guide directed pushing, teaching the birthing person how and when to push most effectively. In some instances, a healthcare provider might perform a manual reduction, gently pushing the anterior lip over the baby’s head during a contraction. While this can be uncomfortable, it is often a quick and effective method to clear the cervix.
Epidural Management
The use of an epidural can sometimes affect the sensation of pushing. If an epidural is in place, the care team can adjust medication levels or provide specific coaching to manage the pushing phase. These interventions are generally successful in resolving an anterior lip, allowing labor to progress towards a vaginal birth.