Normal Labor and Delivery

Labor Definition

• Onset of uterine contractions of sufficient frequency, intensity, and duration to result in effacement and dilation of the cervix

• Effective uterine contractions

  • Last 45-90 seconds, increasing in duration as labor progresses

  • Create 40-100 mmHg

  • Occur every 2-4 minutes

Duration of labor depends on:

• Parity

• Size and position of fetus

• Shape and capacity of pelvis

• Consistency of cervix

  • Firm: cannot push baby out

• Efficiency of uterine contractions

Assessment of patient in labor

• Digital vaginal exam

  • Assessment of cervix

    • Effacement: thinning

    • Dilation: opening

    • Consistency: soft

    • Position of cervix

Effacement

• Thinning and shortening of cervical canal

  • Normal length: 3-4 cm

  • Measured in percentages

• Cervix thins out and softens → length is reduced

• Determine by palpating cervix with finger and estimating length from internal to external os

• Need 50-60% effacement before cervix can open effectively

Dilation

• Opening of the cervix to accomodate the baby

  • Describes the size of the opening of the cervix at the external os

  • Measured in cm (1-10)

  • Ranges from closed (-) to fully dilated (10 cm)

  • Determine by sweeping the examining finger from the margin of the cervix on one side to the other side

• Phases

  • Latent: 0-3 cm

  • Active: 7-8 cm

  • Transition: 8-10 cm

Effacement and Dilation

Consistency

• Ranges from firm to soft

  • Soft: indicated onset of labor

Position

• Describes location of cervix with respect to fetal presenting part

  • Classified as posterior, mid-position, anterior

  • Progresses from posterior to anterior in labor

Position

• Relation of presenting part to fetus to right or left side of birth canal and its direction anteriorly, transversely, or posteriorly

  • Most common is occiput anterior

Sterile speculum exam for:

• Suspected rupture of membranes

• Preterm labor

• Signs of placenta previa

Rupture of membranes

• Premature rupture of membrane (PROM): happened on its own

• Preterm premature rupture of membranes: happens when baby is premature (< 36 weeks)

• Artificial rupture of membranes (AROM): provider manually ruptures membranes

4 ways to test rupture of membranes

• Pooling

  • Sterile speculum inserted into the vagina to evaluate for the presence of amniotic fluid pooling

• Nitrazine paper test

  • Check pH → (+) if paper turns blue

• Ferning test

  • Swab collected and evaluated under microscope: (+) if there is a fern like pattern (salt content of amniotic fluid)

• AmniSure

  • Immunoassay test that detects specific proteins found in amniotic fluid → highly accurate

• Pooling, Nitrazine paper test, and Ferning test usually done together

• Complications → chorioamnionitis

Synclitism

• Optimal fetal head position during labor

  • Head is not tipped to either side

  • Bi-parietal diameter (widest part of the head) is parallel to the plane of the pelvis

  • Sagittal suture is midway between the maternal symphysis pubis and the sacrum

• Affects how the baby moves through the birth canal

Asynclitism

• Fetal head is tipped towards one shoulder laterally, causing it to engage with the pelvis in an uneven, lateral, or oblique angle

• Anterior: anterior parietal bone is closer to pelvis, making the sagittal suture closer to the sacrum

• Posterior: posterior parietal bone is deeper in the pelvis, making the sagittal suture closer to the pubic symphysis

• Severe cases can impede fetal descent

Cardinal Movements of Labor

• Engagement

  • When widest diameter of fetal presenting part has passed through pelvic inlet

  • In most, the bony presenting part is at level of the maternal ischial spines when head becomes engaged

• Descent

• Flexion of head

  • Partial flexion exists before labor → further flexion occurs with descent

• Internal rotation

• Extension

• External rotation

• Expulsion

True Labor Contractions

• Regular and get stronger

• Stronger with walking

• No change laying down

• Back and abdominal pain

• Cervix thins and dilates

• No effect with sedation

False Labor Contractions

• Contractions irregular and short

• No change if walking

• Goes away laying down

• Lower abdominal pain

• No cervical change

• Sedation helps

First stage of labor: onset

• Onset of labor until full effacement and dilation

  • Body getting ready for birth

  • Usually the longest stage of labor

• Latent phase

  • Effacement and early dilation (0-3-4 cm)

  • Contractions mild to moderate, irregular, and gradually increasing in frequency and intensity

  • Strong period cramps or lower back pain

  • Timing depends on history of vaginal birth

    • Nulli: 6-20 hours

    • Multi: 2-12 hours

    • Normal for early labor to stop and start for a stretch of days

  • Prolonged

    • Nullips: > 20 hours

    • Multips: > 14 hours

• Active phase

  • Rapid, progressive cervical dilation

  • Cervix dilates from 6-10 cm

  • Contractions are strong, more regular, and closer together: usually every 2-4 minutes

  • Cervix progresses about 1 cm dilation every 2 hours

  • Duration

    • Nulli: 4-8 hours

    • Multi - 2-5 hours

  • Prolonged active phase

    • < 1cm dilation over 2 hours (especially after 6 cm)

    • May prompt: position changes, hydration, pain management, possible augmentation of labor (Pitocin)

  • Active phase arrest

    • Cervix is >= 6 cm

    • Membranes are ruptured

    • No cervical changes despite

      • 4 hours of adequate contractions OR

      • 6 hours of inadequate contractions with Pitocin

• Medications given

  • Antiemetics: metoclopramide

  • If GBS (+): penicillin

  • Pain control

    • Non-pharmacological: walking, swaying, side lying, lunging, birthing ball or peanut ball, breathing and relaxation, songs

    • Pharmacological

      • Systemic analgesics (IV/IM): opioids (fentanyl, morphine), nitrous oxide

      • Epidural analgesics: blocks pain from uterine contractions and cervical dilation, no longer restricted by cervical dilation

  • Labor Augmentation

    • Prostaglandins (Misoprostol): ripens cervix if it is not favorable (cannot give Pitocin to a firm cervix)

    • Pitocin: stimulates uterine contractions

Second stage of labor: delivery

• Complete dilation of the cervix to the delivery of the infant

• Have intense pushing and delivery of the baby with strong uterine contractions

  • Contractions every 2-3 minutes lasting 60-90 seconds

  • Duration

    • Nulli: 3 hours

    • Multi: 2 hours

    • Longer durations may be normal if progress continues and fetal status is reassuring

• Crowning

  • Widest part of baby’s head remains visible at the vaginal opening between contractions and birth is imminent

  • Pronounced molding of fetal head

  • Further extension under pubic arch

  • Full crown of head emerges

  • Perineum ready to slip over fetal nose, mouth, and chin

  • Controlled birth necessary to avoid sudden compression on fetal head and trauma to maternal tissues (provider may support perineum)

• Molding

  • Changes to the newborns head during labor

  • Shaping and overlapping of bones in the fetal skull as the baby passes through the birth canal → reduces diameter of the head

  • Physiological adaptation to help the baby’s head fit through the maternal pelvis

  • More extreme if infant rotated to posterior position during labor and birth (occiput posterior)

  • Results in elongated or cone-shaped head

  • Usually resolves in hours to days after birth as the cranial bones return to their normal position; no treatment needed

  • Benign; no treatment needed

• Positions

  • Upright: uses gravity, improves pelvic dimensions

  • Hands and knees

• Pain and sensations

  • Strong rectal pressure

  • Stretching or burning at crowning

  • Epidural may reduce urge to push

Third stage of labor: placenta

• Separation and expulsion of placenta

  • Uterus globular and more firm (contracting to prevent postpartum hemorrhage)

  • Sudden gush of blood

  • Umbilical cord protrudes farther out of vagina

• Duration

  • 5-10 minutes from delivery of infant

  • Prolonged if > 30 minutes

• Examining placenta

  • Examine to see if all lobes and membranes are present (cotyledons)

  • Examine for placental abnormalities

• Cord blood samples may be taken

• Involution of uterus → contracts to size of grapefruit after placenta delivers

Fourth stage of labor: postpartum

• The hour or two after delivery when the tone of the uterus is re-established as the uterus contracts again, expelling any remaining contents

Episiotomy

• Intentional surgical incision in perineum made during the second stage of labor to enlarge the vaginal opening for birth

• Not routine anymore

• Indicated if

  • Non-reassuring fetal heart rate requiring rapid delivery

  • Operative vaginal delivery

  • Shoulder dystocia

  • Rigid perineum preventing delivery

  • Breech delivery

• Not recommended for routine prevention of perineal tears, for convenience, for tradition, or to shorten second stage

• Mediolateral

  • Midline and extends diagonally

  • Lower risk of anorectal injury

  • More challenging repair

  • More painful d/t increased tissue damage and involvement of muscle

  • Preferred in situations with higher risk of severe tears, such as operative deliveries (forceps or vacuum) or larger babies

• Midline

  • Midline straight downward

  • Higher risk of tears extending into anal sphincter or rectum

  • Easier repair

  • Good healing/less pain

  • Rare dyspareunia

  • Small blood loss

  • Good anatomic result

  • Preferred in low risk deliveries where the risk of severe tearing is minimal

• Risks and complications

  • Increases blood loss

  • Higher rates of 3rd-4th degree lacerations

  • Postpartum pain

  • Dyspareunia

  • Infection

• Evidence shows that spontaneous tears heal better then routine episiomities

• Repair immediately after with absorbable sutures

Uterine Hemostasis

• Physiologic: uterine muscle fibers contract to constrict blood vessels where the placenta was attached

• Uterine massage: manual massage helps stimulate contractions and expel clots

• Controlled cord traction: gentle pulling on the umbilical cord while applying counter pressure to the uterus (facilitates delivery of the placenta without causing uterine inversion)

• Early cord clamping

  • Cord is clamped and cut within seconds of delivery

  • Shortens third stage of labor but may decrease neonatal blood volume

• Delayed cord clamping

  • Cord is clamped 1-3 minutes after delivery or until pulsations stop

  • Benefits for baby: increased iron stores and improved hemoglobin levels