Practice Essentials
Labor is a physiologic process during which the fetus, membranes, umbilical cord, and placenta are expelled from the uterus.
Stages of labor
Obstetricians have divided labor into 3 stages that delineate milestones in a continuous process.
First stage of labor
Begins with regular uterine contractions and ends with complete cervical dilatation at 10 cm
Divided into a latent phase and an active phase
The latent phase begins with mild, irregular uterine contractions that soften and shorten the cervix
Contractions become progressively more rhythmic and stronger
The active phase usually begins at about 3-4 cm of cervical dilation and is characterized by rapid cervical dilation and descent of the presenting fetal part
Second stage of labor
Begins with complete cervical dilatation and ends with the delivery of the fetus
In nulliparous women, the second stage should be considered prolonged if it exceeds 3 hours if regional anesthesia is administered or 2 hours in the absence of regional anesthesia
In multiparous women, the second stage should be considered prolonged if it exceeds 2 hours with regional anesthesia or 1 hour without it
Third stage of labor
The period between the delivery of the fetus and the delivery of the placenta and fetal membranes
Delivery of the placenta often takes less than 10 minutes, but the third stage may last as long as 30 minutes
Expectant management involves spontaneous delivery of the placenta
The third stage of labor is considered prolonged after 30 minutes, and active intervention is commonly considered
Active management often involves prophylactic administration of oxytocin or other uterotonics (prostaglandins or ergot alkaloids), cord clamping/cutting, and controlled traction of the umbilical cord
Mechanism of labor
The mechanisms of labor, also known as the cardinal movements, involve changes in the position of the fetus’s head during its passage in labor. These are described in relation to a vertex presentation. Although labor and delivery occurs in a continuous fashion, the cardinal movements are described as the following 7 discrete sequences
:
Engagement
Descent
Flexion
Internal rotation
Extension
Restitution and external rotation
Expulsion
History
The initial assessment of labor should include a review of the patient’s prenatal care, including confirmation of the estimated date of delivery. Focused history taking should elicit the following information:
Frequency and time of onset of contractions
Status of the amniotic membranes (whether spontaneous rupture of the membranes has occurred, and if so, whether the amniotic fluid is clear or meconium stained)
Fetal movements
Presence or absence of vaginal bleeding.
Braxton-Hicks contractions must be differentiated from true contractions. Typical features of Braxton-Hicks contractions are as follows:
Usually occur no more often than once or twice per hour, and often just a few times per day
Irregular and do not increase in frequency with increasing intensity
Resolve with ambulation or a change in activity
Contractions that lead to labor have the following characteristics:
May start as infrequently as every 10-15 minutes, but usually accelerate over time, increasing to contractions that occur every 2-3 minutes
Tend to last longer and are more intense than Braxton-Hicks contractions
Lead to cervical change
Physical examination
The physical examination should include documentation of the following:
Maternal vital signs
Fetal presentation
Assessment of fetal well-being
Frequency, duration, and intensity of uterine contractions
Abdominal examination with Leopold maneuvers
Pelvic examination with sterile gloves
Digital examination allows the clinician to determine the following aspects of the cervix:
Degree of dilatation, which ranges from 0 cm (closed or fingertip) to 10 cm (complete or fully dilated)
Effacement (assessment of the cervical length, which can be reported as a percentage of the normal 3- to 4-cm–long cervix or described as the actual cervical length)
Position (ie, anterior or posterior)
Consistency (ie, soft or firm)
Palpation of the presenting part of the fetus allows the examiner to establish its station, by quantifying the distance of the body (-5 to +5 cm) that is presenting relative to the maternal ischial spines, where 0 station is in line with the plane of the maternal ischial spines.
Intrapartum management of labor
First stage of labor
On admission to the Labor and Delivery suite, a woman having normal labor should be encouraged to assume the position that she finds most comfortable. Possibilities including the following:
Walking
Lying supine
Sitting
Resting in a left lateral decubitus position
Management includes the following:
Periodic assessment of the frequency and strength of uterine contractions and changes in cervix and in the fetus’ station and position
Monitoring the fetal heart rate at least every 15 minutes, particularly during and immediately after uterine contractions; in most obstetric units, the fetal heart rate is assessed continuously
Second stage of labor
With complete cervical dilatation, the fetal heart rate should be monitored or auscultated at least every 5 minutes and after each contraction.
Prolonged duration of the second stage alone does not mandate operative delivery if progress is being made, but management options for second-stage arrest include the following:
Continuing observation/expectant management
Operative vaginal delivery by forceps or vacuum-assisted vaginal delivery, or cesarean delivery.
Delivery of the fetus
Positioning of the mother for delivery can be any of the following
:
Supine with her knees bent (ie, dorsal lithotomy position; the usual choice)
Lateral (Sims) position
Partial sitting or squatting position
On her hands and knees
Episiotomy used to be routinely performed at this time, but current recommendations restrict its use to maternal or fetal indications
Delivery maneuvers are as follows:
The head is held in mid position until it is delivered, followed by suctioning of the oropharynx and nares
Check the fetus’s neck for a wrapped umbilical cord, and promptly reduce it if possible
If the cord is wrapped too tightly to be removed, the cord can be double clamped and cut
The fetus’s anterior shoulder is delivered with gentle downward traction on its head and chin
Subsequent upward pressure in the opposite direction facilitates delivery of the posterior shoulder
The rest of the fetus should now be easily delivered with gentle traction away from the mother
If not done previously, the cord is clamped and cut
The baby is vigorously stimulated and dried and then transferred to the care of the waiting attendants or placed on the mother’s abdomen
Third stage of labor
The following 3 classic signs indicate that the placenta has separated from the uterus
:
The uterus contracts and rises
The umbilical cord suddenly lengthens
A gush of blood occurs
Delivery of the placenta usually happens within 5-10 minutes after delivery of the fetus, but it is considered normal up to 30 minutes after delivery of the fetus.
Pain control
Agents given in intermittent doses for systemic pain control include the following
:
Meperidine, 25-50 mg IV every 1-2 hours or 50-100 mg IM every 2-4 hours
Fentanyl, 50-100 mcg IV every hour
Nalbuphine, 10 mg IV or IM every 3 hours
Butorphanol, 1-2 mg IV or IM every 4 hours
Morphine, 2-5 mg IV or 10 mg IM every 4 hours
As an alternative, regional anesthesia may be given. Anesthesia options include the following:
Epidural
Spinal
Combined spinal-epidural