Prolonged labor, often described as “failure to progress,” occurs when the birthing process takes significantly longer than expected. Labor is generally divided into three stages: the first stage involves cervical changes, and the second stage is the pushing phase. Medical terminology defines precisely when the progression of cervical dilation or fetal descent slows or stops, requiring close attention and potential intervention.
How Doctors Define Prolonged Labor
Medical professionals use specific timeframes and progression rates to diagnose prolonged labor, categorized into two main types of dysfunction. A protraction disorder means labor is progressing slowly but still moving forward, while an arrest disorder signifies labor has completely stopped. These definitions apply primarily to the active phase of the first stage of labor, which begins when the cervix reaches 6 centimeters of dilation.
In the active phase, a protraction disorder for a first-time mother is defined as cervical dilation occurring slower than 1.2 centimeters per hour. For mothers who have given birth previously, this threshold is less than 1.5 centimeters per hour. An active-phase arrest is diagnosed when the cervix has not changed for four hours despite adequate uterine contractions, or for at least six hours with inadequate contractions while receiving labor-stimulating medication.
The second stage of labor, the time spent pushing after the cervix is fully dilated, also has defined limits for prolonged duration. For a first-time mother, the second stage is prolonged if it exceeds three hours, or four hours with an epidural. For mothers who have had a prior vaginal delivery, the limit is two hours without an epidural and three hours with an epidural. These timeframes guide the decision-making process, though more time may be allowed if both mother and baby are stable and making progress.
Factors That Contribute to Stalled Labor
Stalled labor is caused by a mismatch or problem in one of the three primary components required for a successful vaginal birth. The first component is the power of the contractions, which must be strong, frequent, and coordinated enough to dilate the cervix and push the baby down. If the uterine muscles contract ineffectively or too weakly, known as uterine dysfunction, labor cannot progress.
The second component is the passage, which refers to the mother’s pelvis and birth canal. If the pelvic structure is too narrow or unusually shaped, cephalopelvic disproportion (CPD) may occur, meaning the baby’s head cannot fit through the bony pelvis. This mechanical obstruction prevents the fetus from descending, regardless of contraction strength.
The final component is the passenger, which is the fetus itself. The baby’s position or size can significantly impede labor progress. The most common issue is fetal malposition, such as the head facing the mother’s abdomen (occiput posterior). An unusually large baby, or fetal macrosomia, can also lead to a physical obstruction in the birth canal.
Health Risks for Mother and Baby
When labor is prolonged, health risks increase for both the mother and the infant, necessitating a diagnosis and treatment plan. For the mother, the extended duration can lead to severe physical exhaustion and dehydration, diminishing the ability to push effectively. A prolonged period with ruptured membranes also raises the risk of infection inside the uterus, known as chorioamnionitis.
Other maternal complications include postpartum hemorrhage, which is excessive bleeding after delivery due to the tired uterus not contracting properly. In rare cases, especially with an obstruction, there is a risk of uterine rupture. For the baby, the primary concern is fetal distress, where prolonged pressure and lack of progress reduce the oxygen supply, leading to an abnormal heart rate pattern.
Extended time in the birth canal increases the baby’s risk of birth trauma and conditions like shoulder dystocia, where the shoulder becomes lodged after the head delivers. If the baby passes stool (meconium) into the amniotic fluid, prolonged labor raises the risk of the baby inhaling this substance, which can lead to breathing difficulties.
Common Medical Interventions
Once prolonged labor is diagnosed, the goal of medical intervention is to safely resolve the dysfunction and proceed with delivery. If the cause is ineffective contractions, the most common intervention is labor augmentation, typically using a synthetic form of the hormone oxytocin (Pitocin). This medication is administered intravenously to increase the frequency, duration, and strength of uterine contractions.
Another common procedure is an amniotomy, or artificially rupturing the membranes (breaking the water), which can stimulate contractions and accelerate labor. If the active phase or pushing stage remains prolonged despite augmentation efforts, the care team may attempt an assisted vaginal delivery. This involves using instruments like forceps or a vacuum extractor to guide the baby through the birth canal.
If labor arrest is due to a structural problem, such as cephalopelvic disproportion, or if augmentation and assisted delivery attempts fail, the final intervention is a cesarean delivery. This surgical birth is performed when the risks of continuing labor outweigh the risks of surgery, especially if there are signs of maternal or fetal distress.