Last updated: August 11, 2022

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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
  • 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]

Overview of the stages of labor
Stage Characteristics Duration Clinical features Management
Nulliparous patients Multiparous patients
First stage of labor Latent phase of labor
  • Occurs during the onset of labor and ends at 6 cm of cervical dilation [7]
  • Characterized by mild, infrequent, irregular contractions with a gradual change in cervical dilation (< 1 cm/hour) [8]
  • ≤ 20 hours
  • ≤ 14 hours
  • 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: a watery discharge (caused by rupture of the amniotic sac) that usually occurs during the onset of labor
  • Delayed rupture of membranes: rupture of membranes that occurs during fetal expulsion, after cervical dilation and effacement
Active phase of labor
Second stage of labor
  • A stage of labor that begins once the cervix is completely dilated and ends with the birth of the infant
  • < 2 hours (< 3 hours in patients who received an epidural)
  • < 1 hour (< 2 hours in patients who received an epidural)
  • 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
Third stage of labor
  • A stage of labor that begins with the birth of the infant and lasts until the complete expulsion of the placenta
  • 30 minutes
  • Uterine contractions (to expel the placenta)
  • Signs of placental separation
    • Cord lengthening
    • Gush of vaginal blood (usually accompanied by a blood loss of 300 mL)
    • Uterine fundal rebound (the uterus becomes less elongated and more spherical)
Fourth stage of labor
  • N/A
  • Uterine contractions
  • Expulsion of any remaining contents


  • 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 )

Overview of abnormal labor

Stage Characteristics Duration Management
Nulliparous patients Multiparous patients
First stage of labor Prolonged latent phase
  • > 20 hours
  • > 14 hours
  • Rest, hydration, and adequate analgesia
  • Oxytocin may be considered in well-rested mothers if the previous measures have been implemented.
  • Other: amniotomy, cervical ripening
Prolonged active phase
Arrested active phase
  • ≥ 6 cm cervical dilation with ruptured membranes and no cervical change after one of the following:
    • ≥ 4 hours of adequate contractions (≥ 200 Montevideo units)
    • > 6 hours of inadequate contractions
  • Usually due to abnormalities of the 3 P's of labor
Prolonged second stage of labor
  • Arrest of fetal descent
  • Usually due to abnormalities of the 3 P's of labor
  • > 3 hours (> 4 hours in patients who received an epidural)
  • > 2 hour (> 3 hours in patients who received an epidural)
  • 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
Prolonged third stage of labor [11]

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

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 [13]

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 [16][17]

Fetal heart rate [18][19][20]

Fetal heart rate variability [21]

  • 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) [20]

  • 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) [16][22][23][24][25]

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

Early deceleration

  • Compression of the head during a contraction triggering a vagal response
  • The beginning and end of decelerations correspond with the progression of a contraction (the deceleration reaches its minimum, referred to as the nadir, when the contraction curve attains its peak).
  • Onset to nadir is gradual (≥ 30 seconds).
  • 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 seconds).
Variable deceleration
  • Variable presentation and temporal relation to the changes in contractions
  • Onset to nadir is abrupt (< 30 seconds) and lasts ≥ 15 seconds but < 2 minutes.
Prolonged deceleration
  • A decrease in FHR of ≥ 15 bpm from the baseline, lasting ≥ 2 minutes but < 10 minutes
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 [18][19][26]

  • Repositioning of the mother, administer O2 and possibly fluids
    • Positions that reduce cord compression: lying on the right or left side, on hands and knees, Trendelenburg position, lateral semi-Fowler's position
    • Manual elevation of the fetal head (fetus is pushed back into the uterus)
    • Consider filling the bladder with saline
  • If initial steps unsuccessful, consider:
  • Delay active pushing during the 2nd phase of labor



Modified Bishop score

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


Obstetric forceps delivery

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


Overview of 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

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.

Cesarean delivery on maternal request (“on-demand”)

  • Overview
    • Primary cesarean delivery that is performed on the mother's request in the absence of medical indications
    • Medically and ethically acceptable if the patient is well-informed
    • Possible reasons include:
      • Fear of the pain of labor
      • Prior negative labor experience
      • Possibility of scheduled delivery
      • Concerns about fetal harm during vaginal birth
    • Physicians are not obliged to perform a non-medically indicated cesarean delivery and may refer the patient to another obstetrician willing to perform the procedure.
  • Approach
    • Explore the reasons behind the request
    • Address concerns about labor and provide information about prenatal childbirth education, obstetric analgesia, and emotional support during labor
    • Lead a balanced discussion about the risks and benefits of cesarean delivery and vaginal birth
    • If the patient insists on having a cesarean delivery, schedule the procedure for after 39 weeks of gestation


Types of incisions [27]
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.

Perineal lacerations

Complications of fourth-degree lacerations include rectovaginal fistulae.

Obstetric nerve injuries [30]

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 footrests 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

  • 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
  • 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


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