Prolonged Labor, Arrested Labor, and Birth Injury

Labor is considered normal when uterine contractions result in progressive dilation and effacement (stretching and thinning) of the cervix. Normal labor progresses slowly through the initial (latent) phase and then, when the cervix is dilated more than four centimeters, the more rapid, active phase of labor begins.

During active labor, the cervix should progressively dilate at a rate of no less than 1.2 cm per hour (during a woman’s first pregnancy) or 1.5 cm per hour (for subsequent pregnancies) (1). If labor progresses more slowly than this, a woman may be experiencing arrested or prolonged labor.

For over 60 years a tool known as the Friedman Curve was used to define normal and abnormal labor. Developed by Dr. Emmanuel A. Friedman, this curve was designed in order to identify women at risk of dangerous vaginal delivery (9, 10). Friedman defined an arrest as cervical dilation of less 1.2 cm/hour for a woman’s first pregnancy, and less than 1.5 cm/hour for a woman who has previously given birth (1).

In 2014, however, a controversial newer definition came into being in order to lower the rates of C-section. This definition states that an arrest can be diagnosed during the active phase of labor if a woman’s membranes have ruptured, she is dilated greater than six centimeters, and she experiences either of the following situations (1):

• A lack of cervical change for four or more hours, despite the presence of normal contractions. Or;
• A lack of cervical change for six or more hours and the absence of adequate contractions.

While this newer definition was adopted by the American College of Obstetrics and Gynecology (ACOG) in 2014, evidence points to the fact that the Friedman Curve may actually be a safer definition of arrested labor. In response to ACOG’s new definition, Friedman and colleagues warned that the new method was not evidence-based, and could potentially lead to “gratuitous exposure of fetus and mother to potentially injurious forces of labor” (11). Because of these risks, the Friedman curve is still used today in medicine and has proven to be safe for many years.

While arrested labor indicates that the labor process has halted entirely, prolonged labor refers to labor that has slowed significantly, and lasts longer than expected. Exact definitions of prolonged first and second stages of labor conflict. Some studies have found that labor is prolonged when the duration of the first and second stages of labor combined is greater than 20 hours for a woman’s first pregnancy and greater than 14 hours for women who have previously given birth (2). Other experts say that prolonged labor occurs after 18-24 hours of the combined first and second stages (2). Prolonged labor is more common in a first pregnancy and in women over the age of 35 years (this is considered “advanced maternal age”) (1).

Prolongation and arrest of labor are primarily due to conditions that cause mechanical impediments or inadequate contractions, both of which are discussed in this section. Listed below are complications that can lead to  prolonged and arrested labor (1, 2):

• Fetal malpresentation: If the baby is not in the cephalic (vertex) position (in which the head is at the lower part of the abdomen) before birth, issues with labor progression can occur.
• Cephalopelvic disproportion (CPD): CPD occurs when there is disproportion between the size of the fetus and the size of the maternal pelvis. This size mismatch can cause labor to slow or stop completely.
• Problems with uterine contractions: Inadequate uterine activity occurs when contractions are either not sufficiently strong or not appropriately coordinated enough to dilate the cervix and push the baby out. Issues with uterine activity can arise due to a pregnancy with multiples, excessive use of painkillers or anesthesia, or a variety of other factors.
• Maternal obesity: Higher maternal BMI (body mass index) is correlated with a longer first stage of labor, as well as a variety of other pregnancy complications.

Signs and symptoms of arrested or prolonged labor include the following (3, 8):

• Labor that extends for more than 14 – 20 hours
• Maternal exhaustion and/or distress; dehydration may be present, and the mouth may be dry due to prolonged mouth breathing
• Pain in the back and sides of the body, radiating out to the thighs due to prolonged strong pressure on the back
• Decrease in labor pains over time as the muscles become fatigued
• High pulse rate due to dehydration, exhaustion, and stress
• Dilation of the large intestines, which can be felt along both sides of the uterus as large, thick, air-filled structures
• The uterus is tender upon touch and does not relax fully between contractions
• Fetal distress may develop
• Abnormal contraction patterns which may include “coupling” (two contractions in rapid succession) or “tripling” (three contractions in rapid succession)

In diagnosing prolonged and arrested labor, the medical team will likely examine the following (1, 2, 3):

• Whether signs and symptoms of the condition are present
• The duration of labor
• The frequency and strength of contractions
• Whether labor is abnormal according to expert standards. A normal course of labor consists of the following stages (1):
  • Stage 1: There are uterine contractions leading to complete cervical dilation. This stage is divided into the latent and active phases. In the latent phase, irregular uterine contractions occur with slow and gradual cervical effacement and dilation. The active phase is demonstrated by an increased rate of cervical dilation and descent of the baby.
  • Stage 2: This is defined as complete dilation of the cervix to the delivery of the infant.
  • Stage 3: Stage 3 involves delivery of the placenta.

When labor progresses slowly or stops completely, risks arise for both the mother and the baby. It is imperative that medical professionals act quickly to prevent serious long-term damage. The following are commonly associated with mismanaged prolonged or arrested labor (1):

Dangers to the fetus:

• Fetal distress due to oxygen deprivation
• Intracranial hemorrhage
• Increased use of forceps or vacuum extractors
• Sepsis
• Long-term risks of the baby developing permanent injuries, such as cerebral palsy, hypoxic-ischemic encephalopathy (HIE), and seizure disorders

Dangers to the mother:

• Intrauterine infections
• Trauma and injuries in the maternal birth passage (cervical tears, vaginal wall tears)
• Postpartum hemorrhage
• Postpartum infection

If a woman has a prolonged active phase of labor, physicians sometimes administer Pitocin; this is a synthetic hormone used to induce labor and strengthen uterine contractions. If used properly, Pitocin can speed up the labor process, effectively treating prolonged or arrested labor.

Physicians may use Pitocin with the intent to avoid the need for C-section delivery; however, it is essential that the risks and benefits of Pitocin use are heavily considered. If administered incorrectly or in high doses, Pitocin can cause tachysystole (excessive uterine contractions) which can jeopardize the baby’s oxygen supply and put both the mother and baby at risk. It is important to note that Pitocin must be used with caution at any dose, and the individual clinical picture should be thoroughly considered before professionals proceed with Pitocin intervention (1).

Artificial rupture of the membranes, or an amniotomy, is a procedure whereby the physician ruptures the woman’s membranes with a finger or special tool in order to accelerate labor (1). There is conflicting evidence regarding the effectiveness of amniotomy in speeding up the labor process.

Used in combination with Pitocin, amniotomy may help to induce or augment labor. However, it is important to note that there are risks associated with both Pitocin (as indicated above) and amniotomy. It has been suggested that amniotomy may treat prolonged or arrested labor because it may promote contractions (4). However, there is no concrete evidence that amniotomy alone can induce labor, shorten labor, or prevent C-sections (5).

The potential benefits of performing an amniotomy must be weighed against the risks of this procedure in order to make an informed decision.

These are instruments that are used to assist in vaginal deliveries. If used properly, they can speed up the delivery of the baby. If used improperly, they can cause traumatic birth injuries, which can be permanent. Injuries associated with improper use of these instruments include the following: hemorrhages (brain bleeds), seizures, Erb’s palsy, hypoxic-ischemic encephalopathy (HIE), and cerebral palsy.

Because of these risks, forceps and vacuum extractors are not often used to manage prolonged or arrested labor (1).

A C-section is performed when a vaginal delivery would put the baby or mother at risk. Some conditions that require the baby to be delivered immediately include fetal distress, uterine rupture, and cord prolapse (6). If labor is arrested in the first stage of labor, or if labor augmentation via Pitocin is unsuccessful, a C-section should be performed (1).

If a woman is at risk of having any type of abnormal labor, intensive clinical monitoring should be done. This includes recording the pulse, blood pressure, fetal heart sound (FHS), and dilation of the cervix. Fetal heart rate strips should be checked frequently. If in spite of the above procedures, labor fails to accelerate, or if fetal distress develops, an emergency C-section should be performed (1, 6).