Labor and Delivery

First Stage of Labor

The first stage of labor is the cervical stage, ending with a completely dilated, fully effaced cervix. It is divided into a latent phase, with slow cervical dilation, and an active phase, with more rapid dilation. The active phase begins once the cervix is dilated to 3 cm. Most women who deliver in the ED arrive while in the active phase of stage 1 or early stage 2 labor ( Fig. 176.1 ). The duration of the first stage of labor averages 8 hours in nulliparous women and 5 hours in multiparous women. During this time, frequent assessment of fetal well-being is important, and continuous external electrical monitoring may help identify fetal distress, allowing for appropriate intervention.

The maternal examination provides a rough guide to gestational age. At 20 weeks’ gestation, the uterine fundus reaches the umbilicus. Approximately 1 cm of fundal height is added per week of gestation until 36 weeks. At that time, the fundal height decreases as the fetus drops into the pelvis ( Fig. 176.2 ). These estimates help establish gestational age rapidly.

The abdominal examination with Leopold maneuvers may confirm the lie of the fetus ( Fig. 176.3 ). Bedside ultrasound can be especially useful in determining fetal position. The determination of the stage of labor depends on examination of the cervix. A sterile approach using sterile gloves, sterile speculum, and povidone-iodine solution is indicated to prevent ascending infection. On pelvic examination, the clinician should determine the following:

• Effacement refers to the thickness of the cervix. A paper thin cervix is 100% effaced.

• Dilation indicates the diameter of the cervical opening in centimeters. Complete, or maximum, dilation is 10 cm.

• Position describes the relationship of the fetal presenting part to the birth canal. The most common position of the head is occiput anterior.

• Station indicates the relationship of the presenting fetal part to the maternal ischial spines ( Fig. 176.4 ).

  

• Presentation specifies the anatomic part of the fetus leading through the birth canal.

In 95% of all labors, the presenting part is the occiput, or vertex. On digital examination, a smooth surface with 360 degrees of firm bony contours and palpable suture lines is noted. Palpation of the suture lines and the fontanels where they join allows the examiner to determine the direction the fetus is facing. Three sutures radiate from the posterior fontanel, and four radiate from the anterior fontanel ( Fig. 176.5 ). The lateral margins are examined carefully for fingers or facial parts that indicate compound or brow presentations.

When the clinician suspects rupture of membranes, a sterile speculum examination is performed. This may reveal pooling of amniotic fluid, a fernlike pattern when the fluid is allowed to dry on a microscope slide, and the use of Nitrazine paper, which should turn blue, indicating an alkaline amniotic fluid (pH > 6). Although vaginal blood, cervical mucus, semen, and infection can interfere with results, sensitivities of Nitrazine paper and ferning for the detection of amniotic fluid are nearly 90%. If vaginal bleeding is evident, digital and speculum examination of the pelvis should be deferred until an ultrasound study can be obtained to rule out placenta previa.

Second Stage of Labor

The second stage of labor is characterized by a fully dilated cervix and accompanied by the urge to bear down and push with each uterine contraction. The median duration of this stage is 50 minutes in nulliparous women and 20 minutes in multiparous women, with the anticipation of a more rapid progression for low-birth-weight premature infants. A prolonged second stage of labor is associated with an increase in maternal complications, including postpartum hemorrhage, infection, and severe vaginal lacerations.

Antenatal Fetal Assessment

During labor and delivery, the identification of fetal distress and appropriate intervention can reduce fetal morbidity and mortality. There are currently three methods of assessing a fetus in utero: (1) clinical monitoring; (2) electrical monitoring; and (3) ultrasonography. External electrical monitoring and ultrasonography merit consideration for use in the care of women laboring in the ED. Both modalities provide real-time information that is helpful for the diagnosis of fetal distress and assistance with intrapartum decision making.

Electronic Fetal Monitoring

Electronic fetal monitoring uses tracings of the fetal heart rate and uterine activity. Documentation of organized cyclic uterine contractions helps confirm true labor and may help diagnose fetal distress. In combination with clinical data, this can portend fetal distress due to hypoxia and provide a window for intervention.

Uterine activity is measured transabdominally by a pressure transducer, creating a recording of the contraction frequency. Because the measurements are indirect, the strength of the contractions correlates poorly with the tracing. The tracings are position and placement sensitive.

Fetal heart rate tracings have several components that can be assessed—baseline heart rate, variability, accelerations, decelerations, and diagnostic patterns.

Baseline Heart Rate

This is the average fetal heart rate during a 10-minute period (in the absence of a uterine contraction) and is the most important aspect of fetal heart rate monitoring. Fetal bradycardia is defined as a baseline rate of less than 110 beats/min; fetal tachycardia is defined as a baseline rate of more than 160 beats/min.

Variability

This can be instantaneous (beat to beat) or long term (intervals ≥ 1 minute). Both types of variability are indicators of fetal well-being. Accelerations occur during fetal movement and reflect an alert mobile fetus. Decreased variability may indicate fetal hypoxemia and acidemia, or it may be a side effect of a wide array of drugs, including analgesics, sedative-hypnotics, phenothiazines, and alcohol.

Decelerations

Decelerations in fetal heart rate are more complicated and should be interpreted according to the clinical scenario. There are three types of deceleration—variable, early, and late ( Fig. 176.6 ). These terms refer to the timing of the deceleration relative to the uterine contraction.

Variable and early decelerations are common and normally represent physiologic reflexes associated with head compression in the birth canal or intermittent cord compression. Variable decelerations that are persistent and repetitive usually indicate repeated episodes of umbilical cord compression. The resultant hypoxia and acidosis may cause fetal distress. Attempts to shift maternal and fetal weight off the umbilical cord by changing position are indicated. If variable decelerations continue, the situation warrants efforts to hasten the delivery or, if obstetric backup becomes available, to perform an emergency cesarean section.

Late decelerations are more serious and most often indicate uteroplacental insufficiency. The tracing contours are generally smooth, with the heart rate nadir occurring well after a maximal uterine contraction (typically, ≥30 seconds afterward). The lag, slope, and magnitude of late decelerations correlate with increasing fetal hypoxia. Late decelerations are particularly ominous in association with poor variability, nonreactivity, and baseline bradycardia. When these findings are present, immediate obstetric consultation for delivery is indicated to prevent further hypoxia.

Diagnostic Patterns

Finally, the emergency clinician should be aware of the significance of sinusoidal tracings. Tracings of this type have low baseline heart rates and little beat to beat variability. The sinusoidal tracing is an ominous finding that is often premorbid. The differential diagnosis includes erythroblastosis fetalis, placental abruption, fetal hemorrhage (trauma), and amnionitis.

Ultrasonography

In the third trimester or during labor, ultrasonography can provide crucial information pertaining to impending delivery, such as the number and position of fetus(es) and fetal heart rate. When a technician and radiologist are available, and if time permits, the gestational age, biophysical profile, amniotic fluid index, and a survey of fetal and placental anatomy may be obtained. The American College of Obstetricians and Gynecologists (ACOG) has published recommendations regarding the indications for ultrasonography in the third trimester ( Box 176.1 ). The parameters of immediate interest in the ED are fetal viability (specifically in utero gestation and fetal heart rate), lie, and presentation. Transvaginal ultrasonography is relatively contraindicated in the peripartum period, particularly in the cases of premature rupture of membranes (PROM) and placenta previa.

BOX 176.1

Third-Trimester Ultrasonography: Possible Indications

• Determine number of fetuses.

• Establish fetal presentation.

• Identify fetal heart motion.

• Locate placenta.

• Measure amniotic fluid.

• Determine gestational age.

• Survey fetal anatomy.

• Diagnose cord prolapse.

• Diagnose cause of third-trimester bleeding.

• Rule out placental abruption.

Delivery

As stage 2 of labor progresses, preparation for delivery should be under way. A radiant warmer should be available and heated. Neonatal resuscitation adjuncts should be available, including a towel, scissors, umbilical clamps, bulb suction, airway equipment (oxygen, bag-mask device with appropriate-sized masks, and tools for endotracheal intubation), and equipment to achieve vascular access. Most deliveries require only basic equipment to cut and clamp the umbilical cord, suction the mouth and nose, and dry and stimulate the infant. A nurse should be at the bedside to coach and provide reassurance to the mother.

The mother is placed in the dorsal lithotomy position and prepared for delivery. The Sims position, or left lateral position with knees drawn toward the mother’s chest and back to the physician, is also an acceptable position. The vulva and perineum are cleared and gently scrubbed with sterile water or saline. A repeated sterile examination to assess labor progression and confirm presentation may be performed. Firm digital stretching of the perineum, particularly posteriorly, may prevent tears and lacerations later in delivery.

Controlled coordinated expulsion with coaching to sustain each push aids with crowning and delivery of the head. The most vulnerable moment is when the fetal head begins to stretch and distend the perineum. Instructing the mother to pant and not push slows the passage of the head and shoulders. The modified Ritgen maneuver may be used to support the perineum and prevent maternal injury: In this technique, a towel-draped, gloved hand is used to stretch the perineum and gently exert pressure on the chin of the fetus. The second hand places pressure on the occiput superiorly, guiding the head into slight extension and positioning it so that its smallest diameter passes through the pelvic outlet. Calm communication between the physician and mother is the best way to maintain control of the delivery.

After the head is delivered, the physician allows the head to rotate toward the maternal thigh and clears the fetal face and airway. Next, the shoulders, usually anterior shoulder first, clear the perineum. The shoulders often deliver spontaneously, with little effort by the physician. Gentle downward traction on the head promotes delivery of the anterior shoulder. A subsequent upward motion pulls the posterior shoulder through the pelvic outlet. If delay occurs in delivery of the shoulders, the potential for shoulder dystocia should be considered.

As the infant clears the perineum, attention focuses on the umbilical cord. The infant should be kept low or at the level of the perineum to promote blood flow into the infant from the placenta. The cord is clamped and cut. Clamps should be placed 4 or 5 cm apart, with the proximal clamp 10 cm from the infant’s abdomen. The cord should be cut at least 1cm from the skin to ensure venous access if the neonate requires resuscitation. Suctioning of the nose and mouth at this time may reduce secretions that can cause increased airway resistance.

The infant is now clear of the mother and can be wrapped in towels and moved to the warmer. Gentle drying with a towel and suctioning usually provide sufficient respiratory stimulation. If not, flicking the soles of the feet and rubbing the back are other modalities. Apgar scores at 1, 5, and 10 minutes after birth should be documented.

Episiotomy

With a controlled delivery, routine performance of an episiotomy is not recommended. It should be performed only for specific indications, such as shoulder dystocia or breech delivery. An episiotomy should be done before excessive stretching of the perineal muscles occurs but near the time of delivery to avoid excessive bleeding. Common practice is to cut the episiotomy when the head is visible during a contraction and the introitus opens to a diameter of 3 or 4 cm. The literature currently recommends a mediolateral incision to avoid perineal tears and rectal involvement ( Fig. 176.7 ).

Third Stage of Labor

The third stage of labor involves the delivery of the placenta and frequent checks of the tone and height of the uterine fundus. Signs of placental separation include the following: the uterus becomes firmer and rises; the umbilical cord lengthens 5 to 10 cm; or there is a sudden gush of blood.

These signs usually occur within 5 to 10 minutes of the delivery of the infant but may extend to 30 minutes. Beyond 18 minutes, the risk of postpartum hemorrhage increases and is up to six times more likely after 30 minutes. Although the placenta may be delivered expectantly, active management reduces the length of the third stage of labor and thereby decreases the risk of postpartum hemorrhage. Active management includes the administration of uterotonic gentle traction of the clamped umbilical cord with mild pressure applied above the symphysis pubis and uterine massage after delivery. Any attempt to deliver the placenta before it separates is contraindicated.

Examination of the umbilical cord and placenta is an essential part of the delivery process and any abnormalities should be noted at this time. The umbilical cord is normally a three-vessel structure, with two umbilical arteries on either side of the single umbilical vein. A two-vessel cord (one umbilical artery) occurs in 1 of 500 deliveries. Common abnormalities of the placenta include accessory lobes and abnormal cord insertion. Visible clots adherent to the uterine aspect may indicate placental abruption and the discovery of an incomplete placenta or membranes should alert the clinician to the possibility of postpartum complications.

Fourth Stage of Labor

The fourth stage of labor refers to the first hour after delivery of the placenta and is a critical period during which postpartum hemorrhage is most likely to occur. The cervix and vaginal fornices should be inspected for deep lacerations as a result of delivery, and repair of any vaginal lacerations should be performed at this time.

Finally, oxytocin is infused to promote contraction of the uterus and control hemorrhage. The uterus is evaluated frequently for tone and massaged transabdominally if any sign of relaxation exists. Oxytocin should not be given before delivery of the placenta because this could result in the trapping of placental fragments or may hinder the delivery of an undetected twin.

Clinical Features

The diagnosis of preterm labor requires the identification of uterine activity and cervical changes before 37 weeks of gestation. Early maternal signs and symptoms include an increase or change in vaginal discharge, pain resulting from uterine contractions (sometimes perceived as back pain), pelvic pressure, vaginal bleeding, and fluid leak.

Diagnostic Testing

If uterine contractions and cervical changes are present, and the estimated fetal weight on ultrasonography is less than 2500 g, the diagnosis of premature labor is likely. The differentiation of false labor from true labor is best done by electrical monitoring. The initial evaluation of a woman with possible preterm labor includes urinalysis, complete blood count, and pelvic ultrasonography. If delivery is not imminent, these studies can be performed under monitoring in the ED or obstetrics area. Whenever possible, these patients should be transferred to a perinatal center with an associated intensive care unit.

Management

A viable fetus and healthy mother are indications for medical management directed toward the prolongation of gestation. Preterm labor should not be postponed with medical management in the cases of fetal compromise, major congenital anomalies, intrauterine infection, placental abruption, eclampsia, significant cervical dilation, or PROM.

The treatment of preterm labor involves multiple modalities and is usually performed outside the ED. Tocolytics and fetal maturation therapy combined with bed rest and hydration are used with the hope of prolonging pregnancy ( Box 176.3 ). When tocolytics are indicated, they should be used in coordination with an obstetric consultant. These patients optimally should be transferred to an appropriate center before delivery, whenever possible, because medical management fails in more than 25% of preterm patients for whom it is attempted. The contraindications to tocolytics should be reviewed before initiation of these therapies ( Box 176.4 ). Any patient receiving tocolytics needs to be monitored for signs of fetal distress. Terbutaline has been associated with serious maternal side effects and deleterious behavioral effects in the offspring after in utero exposure. Terbutaline should be limited to short-term inpatient use.