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Last updated: June 20, 2021

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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. Complications of childbirth include arrest of or prolonged labor, premature rupture of membranes and preterm premature rupture of membranes, and nerve injuries. The clinical status of the mother and fetus should be consistently monitored during childbirth. While vaginal delivery is typically preferred, cesarean delivery may be indicated under certain circumstances.

Obstetric contractions (uterine muscle contractions) [1][2][3]

Overview of obstetric contractions [4][5][6]
Time Characteristics

Uterine contractions during pregnancy

  • Physiological; occurs after 20 weeks of pregnancy
  • Low intensity, high frequency
Braxton Hicks contractions (false labor)
  • Irregular, uncoordinated uterine contractions of moderate intensity (helps with fetal positioning)
  • Frequency: typically ≤ 2 times/hour
  • Duration: ≤ 1 minute
  • Do not increase in frequency, intensity, or duration.
  • Cervical changes are absent
  • Typically stop with rest, walking, and/or a change in position.
  • 3–4 days before birth
  • Irregular contractions of high intensity, which occur every 5–10 min shortly before phase 1 begins. They are responsible for correctly positioning the fetal head in the pelvis.
Labor Stage 1: cervical dilation and effacement
  • Onset of normal childbirth.
  • Coordinated, regular, rhythmic contractions of high intensity; occur approximately every 10 minutes. Shortly before stage 2, they occur every 2–3 min. These contractions are responsible for cervical dilation.
Stage 2: fetal expulsion
  • After complete cervical dilation and effacement
  • Coordinated and regular contractions of high intensity; occur approximately every 4–10 min and are responsible for fetal expulsion. Towards the end of the stage, they occur very often (every 2–3 minutes) and are of higher intensity (≥ 200 Montevideo units).
Stage 3: placental expulsion or afterbirth
  • Several minutes after childbirth
  • Irregular contractions of very low intensity, which force the placenta through the vaginal canal within 30 min after fetal expulsion
  • Several days after childbirth
  • Irregular contractions of varying intensity, which cause uterine involution and bleeding cessation

False labor only requires reassurance.

Stages of labor [1][2][3]

First stage of labor

  • Definition: period from the onset of labor until complete dilation of the cervix has occurred
  • Phases
    • Latent phase of labor
      • Occurs during onset of labor → ends at 6 cm of cervical dilation [7]
      • Characterized by mild, infrequent, irregular contractions with gradual change in cervical dilation (< 1 cm per hour). [8]
      • Duration
    • Active phase
      • Occurs after the latent phase at ≥ 6 cm of cervical dilation → ends with complete (∼ 10 cm) cervical dilation [7]
      • Characterized by an increase in the rate of cervical dilation (1–4 cm per hour)
      • Duration
  • Clinical features
    • Cervix effaces and shortens → cervical dilation
    • Bloody show: A blood-tinged mucous plug may be discharged when the cervix shortens and dilates. [9]
    • Spontaneous rupture of membranes: Watery discharge (caused by rupture of amniotic sac) usually occurs during the onset of labor.
    • Delayed rupture of membranes: rupture of membranes occurs during fetal expulsion, after cervical dilation and effacement
  • Management

Second stage of labor

  • Definition: a stage of labor that begins once the cervix is completely dilated and ends with the birth of the infant
  • Duration
  • Clinical features
    • Completely dilated cervix
    • Regular uterine contractions increasing in frequency and intensity
    • Crowning: the appearance of the fetus's head at the vaginal opening as contractions progress
  • Management
    • Warm compresses and perineal massage
    • Assist the mother to find any comfortable and safe position.
    • Episiotomy: not routinely performed
      • Definition: usually a midline incision of the perineum to enlarge the vaginal opening during delivery
      • Indications: shoulder dystocia, forceps or vacuum-assisted delivery, or vaginal breech delivery
    • Delay cord clamping for ∼ 1 minute; alternatively milk the cord (to enhance blood transfusion to the newborn) [10]

Third stage of labor

  • Definition: stage of labor that begins with the birth of the infant and lasts until the complete expulsion of the placenta
  • Duration: 30 minutes
  • Clinical features

Fourth stage [11]


  • Abnormalities of the 3 P's of labor
    • Pelvis: size and shape of the maternal pelvis (e.g., small bony pelvis)
    • Passenger: size and position of the infant (e.g., fetal macrosomia or abnormal orientation)
    • Power: strength and frequency of contractions (e.g., dysfunctional contractions )

First stage of labor

Prolonged latent phase

  • Diagnostics: poor acceleration phase with a cervical dilation ≤ 6 cm
  • Management
    • Rest, hydration, and adequate analgesia
    • Oxytocin may be considered in well-rested mothers if the other measures have been implemented.

Prolonged active phase

  • Etiology: abnormalities of the 3 P's of labor
  • Diagnostics: ≥ 6 cm cervical dilation without adequate dilation (< 1 cm/2h)
  • Management
    • Augmentation with oxytocin for hypotonic contractions
    • Analgesia for hypertonic contractions

Arrested active phase

  • Etiology: abnormalities of the 3 P's of labor
  • Diagnostics: ≥ 6 cm cervical dilation with ruptured membranes and no cervical change for ≥ 4 hours if adequate contractions (i.e., ≥ 200 Montevideo units) are present; or no cervical change for > 6 hours if only inadequate contractions are present
  • Management: cesarean delivery

Prolonged second stage of labor

  • Etiology: abnormalities of the 3 P's of labor
  • Diagnostics: Failed delivery of the baby after 2 hours in a nullipara and after 1 hour in a multipara (an extra hour may be added if an epidural was administered)
  • Management
    • Augmentation with oxytocin if uterine contractions are inadequate and progress is > 1 cm after 60–90 minutes of pushing
    • Trial of forceps or vacuum delivery if the fetal head is engaged AND maternal contractions are adequate
    • Cesarean delivery if the fetal head is not engaged

Complications of a prolonged second stage are postpartum hemorrhage and a poor neonatal outcome.

Prolonged third stage of labor [12]

If the placenta is incomplete or if an accessory placenta is suspected, manual palpation should be performed and any remaining tissue should be removed by curettage.

Rupture of membranes (ROM) is the rupture of the amniotic sac followed by the release of the amniotic fluid and typically occurs spontaneously during the first stage of labor, signifying the onset of labor. Delayed ROM occurs during, rather than before, fetal expulsion, after cervical dilation and effacement. ROM that occurs prior to the onset of labor in term and preterm pregnancies is discussed below.


Premature rupture of membranes (PROM)

Preterm premature rupture of membranes (PPROM)

Prolonged rupture of membranes

  • Definition: ROM that occurs > 18 hours before the onset of uterine contractions in term or preterm pregnancies
  • Risk factors: young maternal age, smoking, STDs, low socioeconomic status

Clinical features

  • Sudden “gush” of pale yellow or clear fluid from the vagina (may also be a constant leaking sensation)


Management [14]

The management of PROM and PPROM depends on the gestational age and the presence of intraamniotic infection or nonreassuring fetal status.

Unstable patients

Stable patients

Tocolysis is contraindicated in advanced labor (cervical dilation > 4 cm), chorioamnionitis, nonreassuring fetal signs, abruptio placentae, or risk of cord prolapse.

Electronic fetal heart rate monitoring [17][18]

  • Description: widely used diagnostic tool during 3rd 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).
    • Mechanoelectrical measurement of uterine contractions via a pressure transducer, recording in the lower curve in kPa (tocodynagraph)
  • Indications

Fetal heart rate [19][20][21]

Fetal heart rate variability [22]

  • 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.
Overview of fetal heart rate variability
Type Oscillation amplitude Causes
Moderate variability
  • 6–25 bpm
  • Physiological fluctuation of FHR
  • Normal finding
Absent variability
  • Undetectable amplitude
Minimal variability
  • < 6 bpm
Marked variability
  • > 25 bpm
Sinusoidal variability
  • 5–15 bpm
  • FHR wave resembles a sinus wave
Pseudosinosoidal variability
  • Similar appearance to sinusoidal variability
  • Irregularly shape and amplitude of the FHR curves

Acceleration (CTG) [21]

  • 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) [17][23][24][25][26]

  • Description: a temporary decline in the FHR of > 15 bpm for a maximum duration of 3 minutes
Overview of types of fetal decelerations
Types Etiology Characteristics Measures

Early deceleration

  • Compression of the head during a contraction triggering a vagal response
  • The beginning and end of the deceleration corresponds with the progression of a contraction (the deceleration reaches its minimum, known as the nadir when the contraction curve attains its peak)
  • Onset to nadir is gradual (≥ 30 sec)
  • Typically occurs during active labor when the cervix is dilated ≥ 5 cm and the head is engaged within the pelvic cavity
Late deceleration
  • Decrease in the FHR following the maximum contraction curve
  • Onset to nadir is gradual (≥ 30 sec)
Variable deceleration
  • Rather variable presentation and temporal relation to the contractions changes
  • Onset to nadir is abrupt (< 30 sec) and lasts ≥15 sec, but < 2 min
Prolonged deceleration
  • A decrease in FHR by ≥ 15 bpm from the baseline, lasting ≥ 2 min but < 10 min
MNEMONIC for etiology of fetal HR alterations: VEAL CHOP
Variable decelerations → Cord compression/prolapse
Early decelerations → Head compression
Accelerations → OK
Late decelerations Placental insufficiency/Problem

Interpretation and management


Management with intrauterine resuscitation measures [19][20][27]

  • Repositioning of the mother, administer O2 and possibly fluids
  • If initial steps unsuccessful, consider:
  • Delay active pushing during the 2nd phase of labor
Modified Bishop score
0 points 1 point 2 points 3 points
Cervical position Posterior Midline Anterior
Cervical consistency Firm Moderately firm Soft (ripe)
Cervical effacement (thinning of the cervix that occurs during labor. Usually reported in percentages) Up to 30% 31–50% 51–80% > 80%
Cervical dilation closed or 0 cm 1–2 cm 3–4 cm > 5 cm
Fetal station - 3 cm - 2 cm - 1/0 cm + 1/+ 2 cm
  • Approach
    • Membrane sweeping (shortens time to onset of labor)
    • If the cervix is still unfavorable: cervical ripening with prostaglandin E1 or E2 (e.g., misoprostol)
    • Maternal oxytocin infusion
    • Consider amniotomy (only if the cervix is partially dilated and completely effaced, and the fetal head is well applied)
    • Administer under fetal heart rate monitoring.

Obstetric forceps delivery

  • Definition: a forcep is a metal device that enables gentle rotation and/or traction of the fetal head during vaginal delivery
  • Types
    • Kielland: enables rotation and traction of the fetal head
    • Simpson: only enables traction of the fetal head
    • Barton: used for occiput transverse position of the fetal head
    • Piper: used to deliver the fetal head during breech delivery
  • Classification (See “Station” in “Mechanics of childbirth”)
    • Outlet: fetal head lies on the pelvic floor
    • Low: fetal head is below +2 station (not on the pelvic floor)
    • Mid: fetal head is below 0 station (not at +2 station)
    • High: fetal head is not engaged
  • Indications
  • Prerequisites
    • Skilled clinician
    • Clinically adequate pelvic dimensions (see “Mechanics of childbirth”)
    • Full cervical dilation
    • Engagement of the fetal head
    • Knowledge of exact position and attitude of the fetal head
    • Emptied maternal bladder
    • No suspicion of fetal bleeding or bone mineralization disorders
  • Advantages (compared to vacuum delivery)
    • Scalp injuries are less common
    • Cannot undergo decompression and “pop off”
  • Complications

Vacuum extractor delivery

A routine episiotomy is not recommended with assisted vaginal delivery because of the risk of poor healing and anal sphincter injury!

An advantage of assisted vaginal delivery is avoiding cesarean delivery!


  • Definition: the delivery of a newborn through a vertical or horizontal incision in the lower abdominal and uterine wall
  • Advantages
    • Safest method of birth if maternal and/or fetal health is compromised by a vaginal delivery
    • Fetal birth trauma is rare.
  • Disadvantages
  • Indications
Indications for cesarean delivery
Type of cesarean delivery Maternal indications Fetal indications
Primary cesarean delivery
Secondary cesarean delivery(after PROM and/or onset of phase 1)
Emergency cesarean delivery
  • Pathological CTG (particularly persistent, severe fetal bradycardia)
  • Fetal acidosis
  • Immediate threat to life of mother or fetus
  • Types
Types of incisions [28]
Definition Advantages Disadvantages

Low segment transverse

  • ↓ Risk of:
    • Adhesions
    • Hemorrhage
  • Trial of labor in subsequent pregnancy is possible, in the absence of any conditions requiring cesarean delivery
  • Better cosmetic appearance
  • May be performed in the presence of lower segment pathologies (e.g., myoma)
  • Fetus can be delivered regardless of lie
  • Easily allows extension of incision intraoperatively
  • Shorter incision-to-delivery period
  • ↑ Risk of:
    • Rupture in subsequent pregnancies
    • Hemorrhage
    • Adhesions

There are guidelines detailing indications for cesarean delivery that are based on scientific findings. However, each hospital can individually determine how these indications are interpreted. The well-being of the mother and child should be of the utmost priority.

Obstetric lacerations

  • Definition: tear of the perineal body due to significant or rapid stretching forces during labor and delivery; most common obstetric injury of the pelvic floor
  • Risk factors [29]
  • Classification [30]
    • First degree: cutaneous to subcutaneous tissue tear (skin, fourchette, posterior vaginal wall) with no involvement of the perineal muscles
    • Second degree: structures in first degree lacerations and the perineal muscles without involvement of the anal sphincter
    • Third degree: structures in second degree lacerations with involvement of the external anal sphincter → can cause fecal incontinence due to sphincter involvement
    • Fourth degree: structures in third degree lacerations and the anterior wall of the anal canal or rectum
  • Treatment
    • Surgical repair within 24 hours
    • Depending on the degree of severity, local, regional, or general anesthesia can be used.
    • Suturing the torn structures with subsequent digital-rectal examination to assess wound care
  • Complications
  • Prevention: application of warm compress to perineum during delivery and avoidance of risk factors

Complications of fourth degree tears include rectovaginal fistulae.

Obstetric nerve injuries [31]

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

Obstetric nerve injuries
Nerve Clinical Features Risk Factors
Lumbar radiculopathy
Lateral femoral cutaneous nerve injury
Common peroneal nerve injury
  • Prolonged squatting during childbirth
  • Hyperflexion of the knees during childbirth
  • Direct compression of the nerve with direct pressure over the fibular head
  • Inadequate foot rests or stirrups used during vaginal delivery
Pudendal nerve injury


Umbilical cord prolapse

There are 3 types:

Overt umbilical cord prolapse

Occult umbilical cord prolapse

Cord presentation

Nuchal cord [5]

  • Most often caused by activity/turning of the fetus
  • Single cord around the neck: observed in ∼ 20% births
  • Multiple cord loops around the neck: < 1% births

Knotting of the umbilical cord

  • Most often caused by activity/turning of the fetus
  • Cord knot: 1–2% births
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