Chapter 131. Normal Spontaneous Vaginal Delivery

The Emergency Physician will, on occasion, be required to handle the delivery of an infant when an Obstetrician or Family Physician is not available. The management of normal labor and delivery requires a basic understanding of the mechanisms of labor, the assessment and treatment of the mother, the safe delivery of the infant, and careful observation of both in the immediate postpartum period.

Labor is defined as repetitive uterine contractions leading to cervical change (dilation and effacement). The mechanisms of labor, also known as the cardinal movements of labor, describe the changes in the position of the fetal head as it travels through the birth canal. The safe delivery of the infant is the ultimate goal of labor.

Pelvic Anatomy

A successful vaginal delivery is dependent on the adequacy of the female pelvis. Through the use of clinical pelvimetry, physicians are able to make an assessment if adequate space exists for the passage of the fetus during prenatal visits. In theory, the most useful planes to measure are the pelvic inlet and the midplane. Evaluating the pelvic inlet is done by measuring the diagonal conjugate (Figures 131-1A & B). When assessing the midplane, a measurement is taken of the ischial interspinous or bi-ischial diameter (Figure 131-1C). Inadequate measurements indicate potential problems that may result in fetal entrapment, shoulder dystocia, or prolonged labor.1

The diagonal conjugate refers to the distance from the inferior border of the pubic symphysis to the sacral promontory (Figure 131-1A). A normal diagonal conjugate measures approximately 12.5 cm, with the critical distance being 10 cm. To measure the diagonal conjugate place the tip of the middle finger at the sacral promontory and note the point on the hand that contacts the pubic symphysis (Figure 131-1B). The true conjugate, a radiographic measurement of the pelvic inlet, is the distance from the sacral promontory to the superior aspect of the pubic symphysis (Figure 131-1A). However, this measurement cannot be made clinically. The true conjugate can be estimated by subtracting 1.5 to 2 cm from the diagonal conjugate. This distance represents the smallest diameter of the inlet and is normally 11 cm or more (Figure 131-1A). The obstetric conjugate is the distance from the sacral promontory to a point on the inner surface of the pubic symphysis that is a few millimeters from the upper margin of the pubic symphysis (Figure 131-1A). This distance corresponds with the true conjugate and is approximately 11 cm (Figure 131-1A). The critical distance to keep in mind is a diagonal conjugate of 12.5 cm, which corresponds to the desired minimum of an 11 cm true conjugate.

When evaluating the midpelvis, one must measure the ischial interspinous diameter. This can be accomplished by palpating the ischial tuberosities and measuring the distance between them (Figure 131-1C). A value greater than 10 cm is considered adequate.1

While the assessment of maternal pelvic shape may be of clinical utility, it is generally not feasible to take these measurements in the Emergency Department as the patient is often delivering precipitously. In addition, assessment of pelvic shape is an inexact science. A trial of labor is the fundamental way to determine whether a fetus will be able to pass through the maternal pelvis.2 One retrospective review on the performance and utility of routine clinical pelvimetry concluded that clinical pelvimetry does not change management of the majority of pregnant patients.3 Therefore, current practice is to allow all women a trial of labor regardless of pelvimetry results.3 Current practice guidelines suggest that clinical pelvimetry is not effective in predicting the actual occurrence of cephalopelvic disproportion and that performance of pelvimetry is associated with a significant increase in cesarean section rates.4

Fetal Anatomy

The anatomical concepts to consider for a successful delivery include the fetal lie, the fetal presentation, and the fetal position. Fetal lie refers to the longitudinal axis of the fetus in relation to the mother. It can be either longitudinal or transverse.

The fetal presentation refers to the body part of the fetus that can be felt during the vaginal examination. A vertex presentation, also known as occiput, is defined by the ability to palpate the skull. The vast majority of fetuses will present in the vertex position at term. Presentation may also be breech when the fetus is in a longitudinal lie. If this occurs, the Emergency Physician will feel an extremity or the infant's buttocks when performing a vaginal examination. In transverse lie, a shoulder or arm may be the presenting part.

The fetal station is defined as the relationship between the presenting part and the mother's ischial spines. The station is reported as a negative number (0 to −5) if the presenting part lies above the ischial spines. Each number represents a centimeter in distance from the ischial spines. If the presenting part lies below the ischial spines, the station is reported as a positive number (0 to 5). The baby is “engaged” in the pelvis when it reaches 0 station.

The fetal position refers to the relationship of the fetal presenting part (occiput, buttocks, etc.) to the maternal pelvis (Figure 131-2). In the vertex presentation, the fetal occiput is used to determine the fetal position. It is best assessed by a sterile vaginal exam after the mother is completely dilated to palpate the fetus' suture lines. Appreciation of fetal position can have important clinical implications. For example, occiput posterior and occiput transverse fetal malposition can make delivery more difficult. Refer to Figure 131-2 for the different possible fetal vertex positions.

Classification of Labor

Labor is defined as repetitive uterine contractions leading to cervical change (dilation and effacement). Labor is divided into three stages. The first stage of labor is defined as the period from the onset of labor until the cervix is completely dilated. The second stage of labor begins at complete cervical dilation and ends with the delivery of the infant. The third stage of labor is the period from the delivery of the infant until the delivery of the placenta.

First Stage of Labor

The first stage of labor is subdivided into three phases. The first or latent phase is the period between the onset of labor and 3 to 4 cm of cervical dilation. The second phase lasts until cervical dilation is almost complete. The third phase is the final period until maximum cervical dilation.

The average duration of the first stage of labor is approximately 8 hours in nulliparous women and 5 hours in multiparous women. Review all data concerning the patient, including the laboratory data. Reassure the patient if there are no problems detected.

Monitor the fetal heart rate. The American College of Obstetricians and Gynecologists (ACOG) recommends monitoring the fetal heart rate by Doppler immediately following a contraction, every 30 minutes in low-risk pregnancies, and continuously with high-risk pregnancies.5 Suspect fetal distress if the heart rate following a contraction is repeatedly below 120 beats per minute.6

The intensity of a contraction is determined by the degree of firmness that the uterus achieves. Contractions may be palpated or monitored by an external transducer (tocodynamometer) placed upon the mother's abdomen.

Monitor the maternal vital signs during active labor. Obtain a temperature every 2 hours and a blood pressure every 30 minutes.7 Antibiotic coverage (penicillin) for group B streptococcal infection is recommended if the membranes have been ruptured for greater than 18 hours.8 This is also known as prolonged rupture of membranes.6,9

Perform a vaginal examination immediately after the membranes have ruptured if the fetal head is not engaged. Monitor the fetal heart rate following the next contraction after rupture of the membranes to assess for occult umbilical cord compression.6

Second Stage of Labor

The second stage of labor lasts approximately 50 minutes in nulliparous women and 20 minutes in multiparous women. It begins with complete dilatation of the cervix and terminates upon delivery of the infant. The recommendation for heart rate monitoring during the second stage of labor is auscultation at least every 15 minutes for low-risk infants and every 5 minutes for those at high risk.5 Fetal heart rate decelerations may occur with contractions as the head descends.5 Allow labor to continue if prompt recovery occurs as the contraction diminishes. Decelerations may also occur from progressive compression of an umbilical cord around the fetus, premature placental separation, or reduction in uterine blood flow, which will all lead to fetal compromise.10 Prolonged fetal heart rate decelerations are an indication for immediate cesarean section.5–7,9,10

Bearing down is a reflex during the second stage of labor. Coaching may be required for optimal pushing efforts, especially in the presence of epidural anesthesia. Half-flex the patient's legs to increase and improve her pushing efficacy. Encourage the mother to take a deep breath at the onset of a contraction and then push downward or Valsalva. Encourage the mother to rest between contractions, as both the mother and the fetus need to recover from the effects of uterine contractions, breath holding, and the muscular effort.6

The perineum will bulge as the fetus descends into the maternal pelvis. Sponge downward any stool that is expelled with a sterile sponge and diluted soap solution. The woman and the fetus are prepared for delivery when the scalp of the fetus becomes visible at the introitus.

Mechanism of Labor

The fetal head must move in a particular manner with respect to the maternal pelvis in order for a normal vaginal delivery to occur. These movements are known as the mechanism of labor or the cardinal movements of labor (Figure 131-3). These movements are described as engagement, descent, flexion, internal rotation, extension, external rotation, and expulsion (Figure 131-4).

The fetal head is floating free in the amniotic fluid before it engages the maternal pelvis (Figure 131-4A). Engagement is the mechanism by which the widest diameter of the presenting part of the fetus, the biparietal diameter, passes below the plane of the pelvic inlet (Figure 131-4B). This can be confirmed clinically by palpation of the presenting part, both abdominally and vaginally. Bimanual examination will reveal the presenting part at station 0 or at the level of the maternal ischial spines.

The fetal head descends into the maternal pelvis after engagement (Figures 131-4B & C). Descent refers to the downward passage of the presenting part through the maternal pelvis. This is a discontinuous process. The greatest rate of descent occurs near the end of the active phase of labor.

The fetal head flexes as it meets resistance from the cervix, the pelvic wall, and the pelvic floor during passage (Figure 131-4B). The result of flexion is to present the smallest diameter of the fetal head, the suboccipitobregmatic diameter, for passage through the maternal pelvis. This is a passive movement of the fetal head.

Internal rotation results in the fetal occiput moving anteriorly toward the pubic symphysis to assume the occiput anterior position (Figures 131-4C & D). It may rotate, less commonly, posteriorly toward the sacral hollow to assume the occiput posterior position. Internal rotation, like flexion, is a passive movement resulting from the contours of the maternal pelvis.

The fetal head begins extension once it descends to the level of the introitus and has completed internal rotation (Figures 131-4D & E). A combination of the downward force of the contracting uterus and the upward force exerted by the maternal pelvic floor muscles rotates the fetal head in extension around the pubic symphysis. Extension continues until the fetal head is delivered.

External rotation, or restitution, of the fetal head takes place after delivery of the head (Figure 131-4F). It brings the occiput and spine back into the same plane with the shoulders. This can occur to either side depending upon the orientation of the fetus.

Expulsion, or delivery of the fetus, occurs after external rotation (Figures 131-4G & H). The anterior shoulder delivers followed by the posterior shoulder then by delivery of the entire body.

The indications for the performance of a vaginal delivery in the Emergency Department include a patient in active labor without the ability or time to transfer the patient to a delivery unit. The lack of an Obstetrician, Family Physician, Certified Nurse Midwife, or other obstetric practitioner will require the Emergency Physician to perform the delivery.

There are no absolute contraindications to the emergent delivery of the fetus in the Emergency Department. Delivery, however, is preferred in a well-staffed Obstetrics Department, especially when the delivery is complicated with such things as prematurity, breech presentation, or a prolapsed umbilical cord.

General Supplies

• Electronic fetal monitor
• Sterile towels
• Povidone iodine or chlorhexidine solution
• Clock or timer watch
• Sterile perineal drapes
• Sterile gloves
• Needles
• Syringes
• Chromic suture, 2-0 and 4-0
• Vicryl suture, 2-0 and 3-0
• Bulb syringe
• Local anesthetic solution
• Clean towels or blanket for baby
• Umbilical cord clamp
• Sterile scissors to trim umbilical cord
• Infant warmer
• Infant resuscitation equipment

Delivery Instrument Pack

• Bandage scissors
• Four towel clips
• Two Allis forceps
• Four ring forceps
• Six straight Kocher clamps
• Straight Mayo scissors
• Two suture scissors
• Adson forceps, or other forceps with teeth
• Russian forceps, 5.5 inches and 8 inches
• Gelpi retractor
• Two small or medium Richardson retractors
• Two Army-Navy retractors
• Two needle holders, 6 inches
• Placenta basin

Prepackaged obstetric kits are readily available and should be stocked in the Emergency Department. They contain all the required equipment and supplies. These kits may be prepared and packaged by the hospital. Commercially produced, disposable kits are available from several manufacturers.

It is important to obtain a history as part of the initial assessment in an attempt to identify any potential problems and to assess if the gravid woman is actually in labor. The physical examination should include the performance of Leopold maneuvers, bedside ultrasonography, a sterile vaginal examination, and an evaluation to detect whether or not spontaneous rupture of membranes has occurred. A fetal assessment is also important before performing a vaginal delivery.

True Labor versus False Labor

True labor is characterized by contractions that are at regular intervals and that gradually increase with intensity. The interval between contractions decreases as labor progresses. Contractions cause discomfort in the back and upper abdomen. Physical examination reveals that the fetus has descended and the cervix is actively dilating and effacing.

False labor is common in late pregnancy. It is characterized by contractions that are brief, occur at irregular intervals, and whose intensity remains the same. These are often referred to as Braxton-Hicks contractions. These contractions primarily cause discomfort in the lower abdomen. Physical examination often reveals that the fetus has not descended and the cervix is not dilated. False labor contractions can be relieved by hydration and sedation.

History and Physical Examination

When possible, and if time permits, perform a thorough History. Unique aspects of the physical examination of the laboring woman include performing Leopold maneuvers, ultrasonography, a sterile vaginal examination, detection of ruptured membranes if applicable, and a fetal assessment.

Obtain the obstetric history to include gravity and parity, route of delivery for previous pregnancies (i.e., vaginal or surgical), and the length of previous labor. Determine the onset, strength, and frequency of contractions that are occurring. Estimate the number of weeks pregnant or estimated date of confinement. Did the patient experience bloody show, rupture of membranes, or any problems during this pregnancy? Did the patient have access to prenatal care? Does the patient have any general medical problems? What is the HIV status? If the HIV status is unknown, it is important to send a rapid HIV test.

The Center for Disease Control guidelines suggest treating for group B streptococcal (GBS) infection if the GBS status of the laboring mother is unknown and she is ≤37 weeks of gestation, rupture of membranes ≥ 18 hours, or has a temperature ≥ 38.0°C. The following women should be treated for GBS infection: positive maternal GBS culture within 5 weeks of delivery, a previous newborn with GBS-invasive disease, or a history of GBS bacteriuria during pregnancy.11

Leopold Maneuvers

Determine the fetal position and presenting part (i.e., vertex or breech) using the Leopold maneuvers (Figure 131-5). The fetus bends in late pregnancy so that its back is convex, the extremities and neck are sharply flexed, and the fetal arms are crossed across the chest (Figure 131-5A). This posture is assumed so that the growing fetus can fit within the uterine cavity. The lie of the fetus, or its long axis in comparison to the mother, is either longitudinal or transverse. The vast majority of fetuses lie in the longitudinal plane at term. The presentation is the fetal part that is closest to the vagina, as felt through the cervix. The head, buttocks, or feet may be the presenting part if the fetus is in a longitudinal lie. The typical presenting part for a longitudinal lie is the occiput.

Approximately 97% of fetuses will present in the vertex position at full term. The Leopold maneuvers will determine the position of the fetus by identifying specific fetal landmarks or by revealing a specific relationship between the fetus and the mother (Figure 131-5). The use of the Leopold maneuvers has been largely replaced by bedside ultrasonography. Nonetheless, they may still be useful when an Emergency Department bedside ultrasound unit is not available.

Perform the first maneuver, the fundal grip. Stand at the patient's side and face her (Figure 131-5A). Gently palpate the abdomen with the fingertips of both hands to determine which fetal part occupies the uterine fundus. The fetal head is firm, round, freely mobile, smooth, and moves independent of the body. The fetal buttocks are less well defined and can be felt as a large, irregular, and soft structure in the uterine fundus. The purpose of this maneuver is to determine presentation.

Perform the second maneuver, the umbilical grip. Stand at the patient's side and face her (Figure 131-5B). Place both hands on either side of the abdomen. Palpate firmly, gently, and deeply to identify the fetal back as a smooth hard surface and the extremities (also known as the small parts) as small nodular parts. Note the lie of the fetus and the position of the back.

Perform the third maneuver, Pawlick's grip. Stand at the patient's side and face her (Figure 131-5C). Place the thumb and middle finger of the dominant hand just above the pubic symphysis. Palpate to determine the presenting part and its relation to the fetal spine. The fetus will be in a vertex or occiput presentation if the cephalic prominence is palpable on the same side as the small parts (i.e., the head is flexed). The fetus will be in a forehead presentation if the cephalic prominence is palpable on the same side as the spine (i.e., the head is extended). The fourth maneuver must be performed to determine the presentation if the presenting part is fixed and deep within the pelvis.

Perform the fourth maneuver, the pelvic grip, to determine the degree of flexion of the fetal head. Stand at the patient's side and face her feet (Figure 131-5D). Place the tips of the thumb, index, and middle fingers over both sides of the lower abdomen. Palpate firmly, gently, and deeply toward the pelvic inlet with both hands. Determine the head position in relation to the fetal spine and small parts.

Leopold maneuvers can be imprecise, especially in the hands of a Physician not accustomed to the maneuvers. The use of Leopold maneuvers are only 28% sensitive when compared to ultrasound for the verification of the fetal position.12 Obstetricians have largely replaced the Leopold maneuvers with bedside ultrasonography.

Ultrasound for Fetal Presentation

The use of ultrasound is highly recommended to confirm the vertex presentation of the fetus. Place the abdominal probe transversely in the suprapubic region with the probe indicator directed to the patient's right side. Fan the probe caudally to identify the presenting part. The fetal head will be low in the pelvis. The fetal skull will be visible as a hyperechoic, bright white oval image (Figure 131-6). Ensure that this is the fetal head rather than a cross section of abdomen, which can also appear as a bright white circular to oval shaped image. Rotate the ultrasound probe 90° to visualize the fetal skull in a second plane. In this second plane, visualize the fetal head articulating with the trunk.

Sterile Vaginal Examination

A sterile vaginal examination is crucial to accurately assess a woman in labor. Always use sterile gloves to decrease the risk of infection. A sterile vaginal examination can be used to evaluate dilation, effacement, station, fetal position, and the presence of blood. Vaginal bleeding in excess of a bloody show is a contraindication to a digital vaginal examination.

It is important to examine the cervix for dilatation and effacement. Effacement is said to be 50% when the length of the cervix is one-half (or approximately 2 cm long) that of an uneffaced cervix (approximately 4 cm long). It is said to be completely or 100% effaced when the cervix becomes as thin as the lower uterine segment. Dilation is an estimate of the cervical opening expressed in centimeters. The examiner places two fingers in the vagina and spreads apart their fingers until the walls of the cervix are appreciated. Use the distance between the fingers to determine the dilation of the cervix in centimeters. The cervix is completely dilated (i.e., 10 cm) when no cervix can be palpated around the presenting part. The Emergency Physician must be careful in declaring the patient fully dilated once the cervix has dilated beyond the ability of their fingers to spread apart. Take extra care to ensure that no cervix is appreciated by palpating the circumference of the presenting part (i.e., the occiput).

Assessment of the station of the fetal head is vital for understanding how far the fetus has descended. It measures how many centimeters the fetal occiput is above or below the maternal ischial spines. The classification system ranges from −5 to +5 cm. Zero station occurs when the occiput is at the level of the maternal ischial spines. The fetal head above the level of the maternal ischial spines is at a negative station (−1 to −5 cm). The fetal head below the level of the maternal ischial spines is at a positive station (+1 to +5 cm).

Detection of Ruptured Membranes

Three specific examinations are performed if rupture of membranes (ROM) is suspected. This includes pooling, the Nitrazine test, and the fern test. First, perform a sterile speculum examination to look for fluid accumulation, or pooling of fluid, in the posterior vaginal fornix. Swab the pooled fluid and examine it for ferning and Nitrazine positivity. Any fluid present should also be examined for the presence of meconium.

Amniotic fluid is basic (pH 7.0 to 7.5) whereas the vagina and its secretions are acidic (pH 4.5 to 5.5). Touch a sample of the pooled fluid to pH or Nitrazine paper. The pooled fluid is presumed to be amniotic fluid if the color of the Nitrazine paper changes from yellow to blue. Blood, however, is also basic and may give a false-positive result if the sample collected is contaminated.

The final diagnostic test for ruptured membranes, and the most specific, is the ferning test. Place a sample of the pooled fluid on a slide and allow it to air dry. Examine the slide under a microscope. The crystals that make up the amniotic fluid will arborize giving the appearance of fern leaves and thus a positive test.

Fetal Assessment

The normal fetal heart rate (FHR) is between 120 and 160 beats per minute. It can be assessed by auscultation, Doppler, or electronic fetal monitoring (EFM). ACOG has issued guidelines regarding continuous fetal monitoring.5 The false-positive rate of EFM for predicting an adverse outcome is high. The use of EFM is associated with an increase in the rate of operative interventions (i.e., vacuum, forceps, and cesarean delivery).

Although continuous EFM for straightforward and low-risk deliveries is not necessary, EFM is standard practice. Therefore, understanding how to interpret the FHR is an important task. First evaluate the tracing for variability. Variability reflects intact neuromodulation of the heart rate and that the cardiovascular system is robust. Variability is the beat to beat irregularity in the tracing which gives the appearance of a wavy baseline. Variability can be further characterized as absent, minimal, moderate, or marked. Absent variability shows no changes in amplitude from the baseline. Minimal variability shows ≤5 beats per minute (bpm) change, moderate variability shows 6 to 25 bpm change, and marked variability shows ≥25 bpm change. Decreased variability is a sensitive finding and may represent benign processes such as fetal sleep or more concerning etiologies such as fetal hypoxia and acidosis.9

Evaluate the EFM tracing for any accelerations (Figure 131-7). These represent fetal movement. Accelerations are defined as an increase above the baseline of 15 bpm lasting for 15 seconds. Generally, the presence of accelerations provides the clinician with reassurance that the fetus is healthy and withstanding the stress of labor.9

Evaluate the EFM tracing for decelerations. There are two main types of decelerations, late and variable. Late decelerations are shallow, symmetric, U-shaped, and have a gradual fall and rise (Figure 131-8). The deceleration usually begins 30 seconds after the onset of a contraction. The nadir of the deceleration occurs after the peak of the contraction. Late decelerations are a sign of fetal hypoxia. Variable decelerations are the most common type of deceleration encountered during labor and signify compression of the umbilical cord. These decelerations are variable in size, shape, duration, and timing relative to the contraction (Figure 131-9). However, their onset and resolution are generally abrupt and sharp in nature. They are usually preceded and followed by an acceleration.9

The initial step when managing an emergent delivery is to obtain vital signs of the mother and the fetus, if fetal monitoring is available. Explain to the mother the urgency of a delivery in the Emergency Department, including the risks and benefits. Explain what to expect, the procedures that may be performed, and attempt to incorporate maternal cooperation to accomplish a controlled delivery. Obtain intravenous access and send blood to the laboratory to determine a hematocrit, blood type, Rh status, antibody screen, VDRL, rapid HIV, and hepatitis screen. Do not give the patient anything to eat or drink once she enters the Emergency Department as gastric emptying time is delayed in pregnancy.

The most commonly used maternal position for delivery is the dorsal lithotomy position. This position increases the diameter of the pelvic outlet. Place the patient supine with her legs in stirrups or leg holders. Never strap the legs so that quick flexion of the thighs can occur if shoulder dystocia presents. Cleanse the vulvar and perineal area with sterile soap, povidone iodine solution, or chlorhexidine solution if time permits. Apply sterile drapes to only expose the vulvar area (Figure 131-10). Full sterile technique is not required. At a minimum, the Emergency Physician should be wearing sterile gloves, a sterile gown, and a mask with eye protection.

Pain relief for a vaginal delivery can be achieved safely and effectively in the form of perineal infiltration with a local anesthetic agent. The pudendal nerve block is a minor regional block that provides adequate analgesia (Figure 131-11A). Palpate the ischial spine through the vagina. Insert a 20 gauge needle between the index and middle finger using a needle guard (Figure 131-11B). Advance the needle and pierce the sacrospinous ligament (Figure 131-11B). Aspirate to ensure that the tip of the needle is not within a blood vessel. Inject 5 to 10 mL of local anesthetic solution. Repeat this procedure on the contralateral side.

A paracervical block can also be used to provide analgesia. However, it can only be used during the first stage of labor. This technique anesthetizes the Frankenhäuser ganglions that contain all the visceral sensory nerve fibers from the uterus, cervix, and upper vagina. Palpate the lateral vaginal fornix (Figure 131-12). Insert a 20 gauge needle along the finger using a needle guard (Figure 131-12). Advance the needle into the submucosa of the lateral vaginal fornix. Aspirate to ensure that the tip of the needle is not within a blood vessel. Inject 5 to 7 mL of local anesthetic solution. Repeat this procedure on the contralateral side. Paracervical block anesthesia has been associated with a relatively high incidence of fetal bradycardia, usually developing 2 to 10 minutes after the block.

Delivery of the Infant

Coaching may be required for optimal pushing efforts. Flex the patient's legs to increase and improve her pushing efficacy. Encourage her to take a deep breath at the onset of a contraction and then push downward or Valsalva. Advise her to rest between contractions, as both she and the fetus need to recover from the effects of uterine contractions, breath holding, and the muscular effort. The perineum will bulge as the fetus descends into the maternal pelvis. Sponge downward any stool that is expelled with a sterile towel or piece of gauze. The woman and the fetus are prepared for delivery when the scalp of the fetus becomes visible at the introitus.

The fetal head becomes increasingly visible at the introitus as labor progresses. Once the bony occiput can be seen and palpated at the vaginal introitus, apply gentle downward pressure on the occiput to aid in the controlled delivery of the head. The fetal head stretches the vaginal outlet and the vulva until they encircle the largest diameter of the fetal head, known as crowning. Gentle digital stretching of the inferior portion of the perineum may aide delivery. The routine use of an episiotomy for delivery has been discouraged due to increases in third-degree and fourth-degree lacerations. However, an episiotomy can be performed when the baby is crowning if there appears to be inadequate stretching of the perineum. Refer to Chapter 132 for the complete details regarding an episiotomy.

Apply manual perineal support and control the head by performing the modified Ritgen maneuver as the fetal head emerges from the introitus (Figure 131-13). Using a towel-draped hand to protect against fecal contamination, apply pressure on the fetal chin through the perineum, anterior to the coccyx. Place the other hand on the fetal occiput to hold the suboccipital region against the mother's pubic symphysis. This maneuver helps to extend the fetal neck, ease the delivery of the fetus, and reduce the incidence of third-degree and fourth-degree perineal lacerations. However, a recent study did not show a decrease in perineal lacerations with this maneuver.13 Despite this, the premise still holds true that one should control the speed at which the fetal head delivers and ease the pressure on the perineum in an attempt to decrease perineal tears.

After crowning occurs, encourage the mother to push with smaller pulses of force to control delivery of head and minimize perineal trauma. Slowly deliver the fetal head using the modified Ritgen maneuver.6,9 The base of the occiput will rotate, or restitute, toward the posterior aspect of the pubic symphysis while the fetal brow, face, and chin pass over the perineum. Instruct the mother to stop pushing once the head is delivered. Gently rotate the infant's head slightly if this does not spontaneously rotate. The routine intrapartum and peripartum suctioning of the nasal cavities and oropharynx of infants with or without meconium-stained amniotic fluid is no longer recommended.14–16

Pass one hand around the neck of the fetus to assess for a nuchal cord.6,9 The umbilical cord must be unwound from the fetal neck, if present, prior to continuing with the delivery.10 The umbilical cord can be found entangled around the neck in approximately 25% of deliveries.10 Slip it over the infant's head if possible (Figure 131-14). The umbilical cord can occasionally be wrapped so tight around the fetal neck that it cannot be slipped over the head. Carefully grasp and clamp the umbilical cord between two clamps placed 1 to 2 cm apart. Carefully cut the umbilical cord between the two clamps with sterile scissors. Unwind the umbilical cord from around the fetal neck. Immediately deliver the fetus as it no longer can rely on the maternal circulation once the umbilical cord is clamped and cut.

Deliver the body of the fetus (Figure 131-15). Gently grasp the sides of the fetal head with two hands (Figure 131-15). Apply steady and gentle downward traction until the anterior shoulder appears under the pubic symphysis (Figure 131-15A). Apply steady and gentle upward traction until the posterior shoulder is delivered (Figure 131-15B). The use of gentle traction with both these maneuvers is important to avoid brachial plexus injuries.

The rest of the infant will spontaneously deliver once the shoulders are delivered. It is still very important to control the delivery of the body to prevent maternal perineal lacerations. A combination of amniotic fluid, blood, and vernix makes delivery of the infant very slippery. Proper hand positioning is important during the delivery of the body. Position the posterior or left hand underneath the infant's axilla prior to delivering the rest of the body. Use the anterior or right hand to grasp the infant's ankles as they are delivered. This ensures a firm grip on the infant.

Place two clamps on the umbilical cord, approximately 4 to 5 cm from the infant and 1 cm apart. Cut the umbilical cord between the two clamps using sterile scissors. Obtain a 10 to 20 mL sample of umbilical cord blood from the placental end for cord blood pH to determine fetal acid–base status and other required tests.17

Dry the infant while simultaneously stimulating and assessing for appropriate physiological responses. The mother may immediately hold the infant, and if desired breastfeed the infant, while the umbilical cord is cut in an uncomplicated birth. The child should respond well to initial stimulation and have an adequately clear airway and good respiratory effort. The infant can be further dried and stimulated in a warm incubator if necessary. Calculate the APGAR scores at 1 minute and 5 minutes after delivery. If the APGAR scores are low at 5 minutes, they should be repeated every 5 minutes in the immediate postpartum period. The acronym APGAR was coined as a mnemonic learning aid. It stands for Appearance (skin color), Pulse (heart rate), Grimace (reflex irritability), Activity (muscle tone), and Respiration (Table 131-1).

Maternal and Fetal Monitoring

The ACOG recommends that providers evaluate and record the fetal heart rate (FHR) at least every 30 minutes in the active phase of the first stage of labor and every 15 minutes in the second stage in patients without complications or risk factors. On the other hand, if complications (e.g., suspected fetal growth retardation, preeclampsia, and type I diabetes) are present, the ACOG recommends continuous FHR monitoring. If that is not possible, evaluate and record the FHR at least every 15 minutes in the active phase of the first stage of labor and every 5 minutes in the second stage.5 Suspect fetal distress if the heart rate following a contraction is repeatedly below 120 beats per minute. If fetal distress is appreciated, place the mother on oxygen, move her to the left lateral decubitus position, and check for umbilical cord prolapse in the absence of vaginal bleeding. Fetal heart rate decelerations may occur with contractions as the head descends. Allow labor to continue if prompt recovery occurs as the contraction diminishes. Decelerations may also occur from progressive compression of the umbilical cord around the fetus, premature placental separation, or reduction in uterine blood flow; all of which lead to fetal compromise.10 Prolonged FHR decelerations are worrisome and warrant action such as supplemental maternal oxygen, reposition of mother, and immediate delivery of the baby by cesarean section.5

The intensity of a contraction is determined by the degree of firmness that the uterus achieves. The frequency of contractions may be palpated or monitored by an external transducer (tocodynamometer) placed upon the mother's abdomen. Remember to monitor the maternal vital signs during active labor and intervene as needed when abnormal vital signs present themselves.

Delivery of the Placenta

Watchful waiting until the placenta separates from the uterus is an acceptable practice if there is no unusual bleeding after delivery of the infant. Watch for the signs of placental separation during expectant management. These include a firm and globular uterus, a sudden gush of blood, uterine elevation in the abdomen, and a lengthening of the umbilical cord. These signs are generally present within 5 to 10 minutes after delivery of the infant, but up to 30 minutes is still within normal limits. Times longer than 30 minutes raise concern for a potential retained placenta.

Some Physicians may choose to actively manage the third stage of labor with early clamping of the umbilical cord, applying controlled umbilical cord traction, and the administration of a uterotonic drug such as oxytocin in an effort to stem postpartum hemorrhage.18,19 The literature is mixed with respect to whether or not active management of labor is beneficial when compared to expectant management.18–20

Instruct the patient to bear down when the placenta has separated. This results in increased intraabdominal pressure that aids in expelling the placenta. Apply suprapubic pressure (Figure 131-16A). Apply gentle traction on the umbilical cord to keep it taut without the use of excessive traction (Figure 131-16A). Aggressive traction on the umbilical cord can result in disruption of the placenta, uterine inversion, or tearing of the umbilical cord; all of which can result in excessive bleeding. Apply suprapubic pressure as the placenta exits the uterus helps to prevent uterine inversion (Figure 131-16B). Deliver the placenta from the uterus (Figure 131-16C). Take care to prevent tearing of the placenta and its membranes as it passes through the introitus. Grasp the placenta and membranes with your hands or ring forceps and guide them out the vagina with gentle twisting traction (Figure 131-16D). Gently massage the uterus through the anterior abdominal wall to maintain uterine contraction. Carefully examine the maternal surface of the placenta for completeness. Any missing pieces represent retained products and must be removed.

Operative vaginal delivery involves the use of forceps or vacuum extractors. This mode of delivery is sometimes controversial, but it can be a safe and effective technique for delivery.6,9 The use of forceps and vacuums is beyond the scope of this chapter.

Vaginal lacerations are classified as first, second, third, or fourth degree.6,9 First-degree lacerations involve the fourchette, perineal skin, and vaginal mucous membrane but not the underlying fascia or muscle. Second-degree lacerations involve the above plus the fascia and muscles of the perineal body but not the anal sphincter. Third-degree lacerations involve the anal sphincter, while fourth-degree lacerations extend through the anal mucosa. The repair of vaginal lacerations is beyond the scope of this chapter. Refer to Chapters 132 and 135 for the complete details regarding laceration repair.

The hour immediately following delivery is often referred to as the fourth stage of labor. It is a critical time. The mother is at risk for hemorrhage, most commonly the result of uterine atony or lacerations of the birth canal. Investigate any unusual bleeding immediately. Administer 20 units of oxytocin, in 1 L of normal saline, intravenously to prevent uterine atony and postpartum hemorrhage. Persistent vaginal bleeding can be managed with additional intravenous oxytocin, 0.2 mg of methylergonovine (Methergine) intramuscularly, or 0.2 mg of prostaglandin F-2 alpha (Hemabate) intramuscularly. Refer to Chapter 135 for the complete details of postpartum hemorrhage management.

Numerous complications can result during the delivery of an infant. These may affect the infant, the mother, or both.

Umbilical Cord Prolapse

The examiner's hand should not be removed if the initial vaginal examination reveals a prolapsed umbilical cord. Elevate the fetal presenting part away from the prolapsed umbilical cord and place the patient in the Trendelenburg position. This reduces compression of the umbilical cord and optimizes blood flow to the fetus. Immediately transport and prepare the patient for an emergent cesarean section while keeping the examiner's hand in place.

Shoulder Dystocia

The shoulders may occasionally impact at the pelvic outlet after delivery of the head. This may occur with delivery of large infants that have larger shoulders compared to their head circumference. Complications of shoulder dystocia include brachial plexus injuries, fetal hypoxia, and compression of the umbilical cord. Place the mother in the extreme lithotomy position, with her legs sharply flexed up to the abdomen (McRoberts maneuver). An episiotomy may also be made to assist in the delivery. Instruct an assistant to apply suprapubic pressure to help disimpact the anterior shoulder from the pubic symphysis. Refer to Chapter 133 for the complete details regarding the management of shoulder dystocia.

Breech Presentation

The breech presentation is associated with a higher incidence of fetal distress and umbilical cord prolapse. It usually occurs in premature infants as the final rotation in the uterus may have not yet occurred. The major concern of breech deliveries is entrapment of the head because of an incompletely dilated cervix. Do not pull on the fetus. This may put additional pressure on the head or further entrap an extremity. Obtain immediate Obstetrical assistance. Refer to Chapter 134 for the complete details regarding breech deliveries.

Preterm Delivery

Delivery of the preterm fetus must be controlled and slow, reducing the likelihood of trauma to the fragile infant. Immediately dry and warm the preterm infant while making an initial assessment. Resuscitation should occur, even for extreme prematurity, until the determination of viability is made.

Postpartum Hemorrhage

Significant bleeding can occur from cervical lacerations, uterine atony, retained products, or first-degree through fourth-degree lacerations. Perform a thorough search for the cause of the postpartum hemorrhage. Refer to Chapter 135 for the complete details regarding the evaluation and management of postpartum hemorrhage.

Injuries to the Infant

A variety of injuries can occur to the fetus during the delivery process. These include abrasions, lacerations, bruising, skull fractures, cephalohematomas, intracranial hemorrhage, brachial plexopathies, nerve injuries, clavicle fractures, humerus fractures, femur fractures, spinal cord injuries, and visceral injuries. Most of these can be prevented by using appropriate techniques and care when delivering the infant.

The Emergency Physician will occasionally be required to perform a delivery of a baby when the Obstetrician or Family Physician is not available or when delivery is imminent. Fortunately, births in the Emergency Department are rare and most proceed with good outcomes. Knowledge of the normal labor and delivery mechanics aids in a safe delivery and helps to identify complications. The Emergency Physician must develop strategies to treat potential complications and must be prepared to intervene.