Normal labor and delivery

Childbirth begins with the onset of labor, which consists of contractions that lead to progressive cervical dilation and effacement, eventually resulting in the birth of the infant and expulsion of the placenta. The process of normal childbirth depends on a high degree of anatomical and physiological compatibility between the mother and child. The birth canal is the passage consisting of the mother's bony pelvis and soft tissues through which a fetus passes during vaginal delivery. Fetal orientation during childbirth is described in terms of lie, presenting part, position, attitude of the presenting part, and station. The clinical status of the mother and fetus should be consistently monitored during labor and delivery. While vaginal delivery is typically preferred, cesarean delivery may be indicated under certain circumstances. Complications of normal vaginal delivery include perineal lacerations, hemorrhage, nerve injuries, and coccydynia.

See “Abnormal labor and delivery” for intrapartum complications and their management.

Fetal lie

• Definition: relation of the fetal long axis to the long axis of the maternal uterus
• Types
  • Longitudinal lie: fetus is in the same axis (most common)
  • Transverse lie: fetus is at a 90° angle
  • Oblique lie: fetus is at a 45° angle

Fetal presentation

• Definition: part of the fetus that overlies the maternal pelvic inlet
• Types
  • Cephalic presentation: head (most common)
  • Breech presentation: buttocks or feet
    • Frank breech: flexed hips and extended knees (buttocks presenting)
    • Complete breech: thighs and legs flexed (cannonball position)
    • Single Footling breech: hip of one leg is flexed and the knee of the other is extended (one foot presenting)
    • Double Footling breech: both thighs and legs are extended (feet presenting)
  • Compound presentation: ≥ 1 anatomical presenting part (e.g., cephalic or breech presentation with presentation of an extremity)
  • Shoulder presentation: shoulder presentations combined with a transverse or oblique lie

Fetal position

• Definition: relationship and orientation (i.e., fetal occiput pointing towards maternal left or right) of the presenting fetal part to the maternal pelvis
• Types
  • Occiput anterior position: Fetal occiput points towards maternal symphysis pubis; fetus faces downwards.
    • Left occiput anterior (LOA): Fetal back faces the maternal left, anterior fontanelle faces the maternal right, sagittal suture lies in the right oblique diameter; (most common position).
    • Right occiput anterior (ROA): Fetal back faces the maternal right, anterior fontanelle faces the maternal left, sagittal suture lies in the left oblique diameter.
  • Occiput posterior position: Fetal occiput points towards the maternal sacral promontory with face to pubis symphysis; the fetus faces upward
  • Sacrum in breech presentation
  • Mentum (chin) in extended cephalic (face) presentation

Fetal attitude ^[1]

• Definition: degree of extension/flexion of the fetal head during cephalic presentation
• Types
  • Vertex presentation (maximally flexed); most common attitude
  • Brow presentation (partially extended)
  • Face presentation (maximally extended)
    • Mentum anterior face presentation : Spontaneous vaginal delivery is possible .
    • Mentum posterior face presentation
  • Forehead presentation (partially flexed; military attitude): Spontaneous vaginal delivery is possible .

Station (Obstetrics) ^[2]

• Definition: measurement (in cm) of the presenting part above and below the maternal ischial spine

  Station	Description
  0	the presenting part is at the level of the ischial spines
  -1, -2, -3	1, 2, and 3 cm above the level of the ischial spines, respectively
  +1, +2, +3	1, 2, and 3 cm below the level of the ischial spines, respectively

• Engagement (Obstetrics)
  • When the widest transverse diameter of the head (presenting part) passes through the pelvic inlet
  • Use the rule of fifths: engagement is clinically identified when ≤ 2/5 of the fetal head are felt above the symphysis pubis through the maternal abdomen

Synclitism

• Definition: parallelism between the pelvic plane and the plane of the fetal head
• In asynclitism, the sagittal suture is in the transverse diameter of the pelvic inlet and not between the symphysis pubis and sacral promontory.
  • Anterior asynclitism (Naegele obliquity)
    • The sagittal suture is positioned towards the sacral promontory
    • Spontaneous vaginal delivery possible
  • Posterior asynclitism (Litzmann obliquity)
    • The sagittal suture is positioned towards the symphysis pubis
    • Normal vaginal delivery is impossible. → premature cesarean delivery

Obstetric contractions (uterine muscle contractions) ^[3][4][5]

False labor only requires reassurance.

Rupture of membranes (ROM)

• Definition: the rupture of the amniotic sac followed by the release of amniotic fluid
• Spontaneous rupture of membranes: ROM that usually occurs at the onset of labor and is unprovoked by health practitioners
• Artificial rupture of membranes (amniotomy): A procedure in which the amniotic sac is ruptured in order to release amniotic fluid.
• Delayed rupture of membranes: ROM that occurs during fetal expulsion, after cervical dilation and effacement
• Abnormal rupture of membranes
  • Premature rupture of membranes (PROM)
  • Preterm premature rupture of membranes (PPROM)
  • Prolonged rupture of membranes
• Clinical features: sudden “gush” of pale yellow or clear fluid from the vagina (may also be a constant leaking sensation)
• Diagnostics
  • Consider sterile speculum examination if the diagnosis is uncertain.
  • Suggestive findings include pooling, positive litmus test or nitrazine test, and ferning.

Stages of labor ^[3][4][5]

Management of labor by stage

• First stage of labor
  • Analgesia upon request
  • Fetal heart rate monitoring
  • Determine fetal position via abdominal (see Leopold maneuvers) and pelvic (palpation of fetal sutures/fontanelles) examination.
    • If the fetal position cannot be determined by examination, perform ultrasound.
  • Regular assessment of cervical dilation and descent of the fetal head
  • Amniotomy may be performed during the active phase if the fetal head is well applied (lying against the cervix).
  • In case of heavier bleeding but normal maternal vital signs and fetal heart tracing (e.g., increased bloody show), delivery should proceed as planned with frequent observation.
• Second stage of labor
  • Warm compresses and perineal massage
  • Helping the mother to find comfortable and safe positions
  • Guide the delivery of the fetus through vaginal canal (See “Mechanics of childbirth” for expected fetal movements).
  • Delay cord clamping for ∼ 1 minute; alternatively, milk the cord (to enhance blood transfusion to the newborn). ^[11]
• Third stage of labor
  • Fundal massage: massaging of the uterine fundus to induce its contraction and stop bleeding
  • Active management of the third stage of labor (reduces the risk of postpartum hemorrhage)
    • Oxytocin, administered after cutting the umbilical cord (reduces blood loss by inducing stronger uterine contractions)
    • Controlled cord traction while allowing the placenta to separate spontaneously (Brandt-Andrews maneuver)
  • Examine the placenta to confirm completeness (regular surface with complete cotyledons), which should also consist of the umbilical cord, complete amniotic membranes, and three blood vessels (one vein, two arteries).
  • Repair any obstetric lacerations.
• Fourth stage of labor: Monitoring to rule out postpartum hemorrhage or preeclampsia

Normal mechanics of childbirth ^[1]

Adaptation to the different forms of the pelvic region requires a great deal of rotation.

1. Engagement, descent, and increased flexion (occur simultaneously)
   • The head engages below the plane of the pelvic inlet.
   • The presenting part begins to descend into the birth canal.
   • The chin of the fetus moves towards its chest.
2. Internal rotation: The fetal head rotates by 90° (two 45° steps) in the midpelvis, from a transverse to anterior-posterior position.
3. Extension: The fetal head, lying behind the symphysis pubis bone and the pelvic floor, acts upwards and forwards.
4. Restitution: The fetal head rotates 45° in the opposite direction as it passes through the pelvic outlet.
5. External rotation: The anterior shoulder rotates 45° anteriorly as it meets the maternal pelvic floor. This action is transmitted to the head which also rotates 45°, placing the head in its original transverse position.
6. Expulsion: Delivery of the head, anterior shoulder followed by the posterior shoulder, and the body

Electronic fetal heart rate monitoring ^[12][13]

• Description: widely used diagnostic tool during 3^rd trimester and labor to detect signs of fetal distress
• Procedure
  • Determination of the fetal heart rate (FHR), presence of acceleration or deceleration by Doppler ultrasound, recording beats per minute (bpm) in the upper curve (cardiogram)
  • During birth, the FHR may be monitored internally via an electrode that is attached to the fetal head (fetal scalp electrode monitoring).
    • Rupture of the membranes must have occurred or an amniotomy performed
    • Used when external monitoring is difficult (e.g., maternal obesity, polyhydramnios, multiple gestations)
  • Mechanoelectrical measurement of uterine contractions via a pressure transducer, recording in the lower curve in kPa (tocodynagraph)
• Indications
  • During labor
  • Admission in the labor ward
  • In every case of complication during pregnancy or delivery, such as impending preterm birth, abnormalities of the fetal heart, multiple pregnancy, suspected placental insufficiency, uterine bleeding, tocolysis

Fetal heart rate ^[14][15][16]

• In CTG, the FHR is designated as the baseline or basal heart rate and is normally 110–160 bpm.
• Tachycardia
  • Mild tachycardia: FHR of 160–180 bpm for > 10 minutes
  • Severe tachycardia: FHR of ≥180 bpm for > 10 minutes
  • Causes: stress, hypotension, maternal fever; , medication (e.g., betamimetics for the treatment of tocolysis), chorioamnionitis, fetal arrhythmias, fetal anemia, hypoxia
• Bradycardia
  • Mild bradycardia: FHR of < 110 bpm for > 3 minutes
  • Severe bradycardia: FHR of < 100 bpm for > 3 minutes
  • Causes: supine hypotensive syndrome, fetal heart defects; , central nervous system anomalies, severe hypoxia
• Methods to assess FHR: Nonstress test (NST) and contraction stress test (CST); are performed during the third trimester of pregnancy to measure FHR reactivity to fetal movements and FHR reactivity in response to uterine contractions respectively. See nonstress test and contraction stress test in “Prenatal care” for details.

Fetal heart rate (FHR) tracing

Fetal heart rate variability ^[17]

On CTG, variability of FHR is represented by the oscillation of the FHR around the baseline and is determined by measuring the amplitude between the highest and lowest turning point of the FHR curve.

Acceleration (CTG) ^[16]

• Description: a normal temporal increase in the FHR from the baseline by > 15 bpm for more than 15 seconds but less than 10 minutes if the gestational age is > 32 weeks, or by > 10 bpm for more than 10 seconds if the gestational age is < 32 weeks
• Interpretation
  • The presence of > 2 accelerations within a span of 20 minutes indicates a reactive fetal heart rate tracing.
  • If the acceleration lasts longer than 10 minutes, it should be considered a baseline change in the fetal heart rate.

Decelerations (CTG) ^{[12][18][19][20][21]}

• Description: a temporary decline in the FHR of > 15 bpm for a maximum duration of 3 minutes

Consider umbilical cord compression or umbilical cord prolapse in patients with recurrent variable decelerations (≥ 50% of contractions).

Interpretation

• Nonreassuring fetal status
  • Characteristic changes in the fetal heart rate (FHR) in response to fetal hypoxia and metabolic acidosis
    • Fetal tachycardia (FHR > 160–180/min)
    • Fetal bradycardia (FHR < 110/min)
    • Loss of baseline variability
    • Recurrent variable decelerations and/or late decelerations
  • A nonreassuring tracing requires intrauterine resuscitation and/or immediate delivery (cesarean or, if imminent, vaginal delivery).
• Reassuring fetal status
  • A fetal heart tracing that shows a good beat to beat variability (> 6 bpm), > 2 accelerations within a 20 minute period, and no evidence of fetal distress (e.g., fetal bradycardia, fetal tachycardia, late or variable decelerations, sinusoidal pattern)
  • Indicates fetal well-being.

Management

See “Intrauterine resuscitation” for details.

• Initial management includes repositioning of the mother, supplemental O₂, fluids, and delayed active pushing in the second stage of labor.
• Consider amnioinfusion, tocolytics, and emergency cesarean delivery if initial measures are unsuccessful.

Perineal lacerations

• Definition: tear of the perineal area due to significant or rapid stretching forces during labor and delivery
• Epidemiology: most common obstetric injury of the pelvic floor
• Risk factors ^[23]
  • Macrosomia
  • Forceps delivery
  • No previous delivery
  • Prolonged second stage of labor
  • Occiput posterior delivery
  • Rapid delivery of head in breech presentation
  • Head extension before crowning
  • Lack of perineal elasticity (e.g., perineal edema)
• Classification ; ^[24][25]
  • First degree: cutaneous to subcutaneous tissue tear (skin, fourchette, posterior vaginal wall) with no involvement of the perineal muscles
  • Second degree: first-degree lacerations plus laceration of the perineal muscles without involvement of the anal sphincter
  • Third degree: second-degree lacerations plus involvement of the external anal sphincter (may lead to fecal incontinence due to sphincter involvement)
    • A: < 50% of the external anal sphincter is torn.
    • B: > 50% of the external anal sphincter is torn.
    • C: external and internal anal sphincters are torn.
  • Fourth degree: third-degree lacerations plus lacerations of the anterior wall of the anal canal or rectum
• Clinical features: symptoms of a missed perineal laceration (occult perineal laceration) may manifest immediately or up to months after delivery ; ^[26]
  • Perineal edema/hematoma, dysuria
  • Symptoms of pelvic floor dysfunction (e.g., fecal/flatus incontinence, pelvic organ prolapse)
  • Signs of infection (e.g., foul-smelling discharge, fever, persisting pain)
• Diagnosis
  • Digital rectal examination findings
    • A palpable defect
    • Decreased anal sphincter tone and/or asymmetric sphincter contractions
  • Endoanal ultrasonography: to evaluate the integrity of the internal and external anal sphincter
• Treatment
  • First and second degree: Minor tears (e.g., superficial, hemostatic lacerations) are left to the clinician’s discretion to determine if suturing is required. ^[27]
    • Conservative: e.g., NSAIDs, sitz baths
    • Suture: local anesthesia and laceration closure using surgical glue or continuous sutures
  • Third and fourth degree
    • Regional or general anesthesia may be used.
    • Reconstructive surgery to repair the anal sphincters and mucosa
    • Reconstruction of the distal rectovaginal septum and the perineal body
• Complications ^[28]
  • Primarily associated with third- and fourth-degree lacerations.
  • Complications include:
    • Pain and dyspareunia
    • Rectovaginal fistulae
    • Hemorrhage
    • Infection
    • Wound dehiscence
• Prevention: application of warm compress to perineum during delivery

Complications of fourth-degree lacerations include rectovaginal fistulae.

Obstetric nerve injuries ^[29]

Acute nerve injury can occur during childbirth due to compression, transection, traction, or vascular injury to the nerve.

Coccydynia

• Etiology: injury to the coccyx during childbirth as a result of internal and external pressure on the coccyx during labor and delivery
• Clinical features
  • Pain and tenderness of the coccyx, esp. when sitting or leaning back
  • Pain may suddenly increase when the patient is changing from a sitting to a standing position.
  • Pain may also occur during defecation or sexual intercourse.
  • Physical examination: palpation of the coccyx elicits pain
• Diagnosis: clinical
• Management
  • Protection (e.g., sitting on Donut or wedge cushions)
  • Analgesics (e.g., NSAIDs)
  • Local heat or cooling according to patient preference
  • Exacerbating factors (e.g., sitting on hard surfaces, cycling) should be avoided if possible.
• Prognosis: resolves spontaneously in the majority of patients (> 90%) ^[30]

Postpartum retroperitoneal hematoma

• Epidemiology: rare (∼ 1:1000) ^[31]
• Etiology: injury to branches of the internal iliac artery (most commonly, uterine artery)
  • Most commonly due to:
    • Laceration of a uterine artery during hysterotomy or uterine rupture
    • Extension of a paravaginal hematoma into the retroperitoneal space
  • Other: pelvic or abdominal injury, anticoagulation, rupture of an aneurysm of the abdominopelvic vasculature
• Clinical features
  • Signs of hemodynamic instability (e.g., tachycardia, hypotension)
  • Usually painless (unless caused by pelvic or abdominal injury)
• Diagnostics: imaging (e.g., sonography, CT)
• Management
  • Prompt laparotomy
  • Alternatively: selective arterial embolization

• Statistics
  • In the US, approx. 1% of births per year are home births.
  • 75% of these home births are planned.
• Indications
  • There is insufficient evidence to determine what makes a good candidate for a home birth.
  • Home births can be considered in individuals with no contraindications.
  • Patients who would like to plan a home birth should be advised about the benefits and risks of home birth compared to hospital delivery in order to make an informed decision.
• Advantages compared to hospital delivery
  • Lower risk of maternal interventions (e.g., induction or augmentation of labor, episiotomy, cesarean delivery)
  • Lower risk of certain maternal complications (e.g., vaginal or perineal lacerations, peripartum or postpartum infections)
  • Lower costs
  • Familiar environment for the mother
• Disadvantages compared to hospital delivery
  • Higher risk of perinatal death for both the mother and fetus
  • Higher risk of neurological complications for the newborn
• Contraindications
  • Absolute contraindications
    • Fetal malpresentation (e.g., breech presentation)
    • Multiple gestation pregnancy
    • Previous cesarean delivery
  • Relative contraindications
    • Any other risk factor for a complicated pregnancy (see “High-risk pregnancies”)
    • No means for safe and timely transport to a nearby hospital or accredited birth center
    • Lack of access to home-birth provider services (e.g., certified professional midwife, certified nurse midwife, obstetrician, family medicine physician)

References:^[32][33]