First Stage of Labor

By: Dr. Ayman Bukhari

House officer Obstetrics & Gynaecology

Contents:IntroductionStages of laborDiagnosisManagement on admissionActive management of laborMonitoringPartogramAbnormalitiesPain control

IntroductionLabor : Uterine contractions resulting in

progressive dilation and effacement of the cervix and accompanied by descent and expulsion of the fetus.

Abnormal labor, dystocia, and failure to progress are terms used to describe a difficult labor pattern

Approximately 20 % of labors involve dystocia

Stages of labor

NORMAL LABOR —  divided into Four stages First stage: time from the onset of labor until

complete cervical dilatation Second stage: time from complete cervical

dilatation to expulsion of the fetus Third stage: time from expulsion of the fetus

to expulsion of the placenta Fourth stage: the 1st post partum hour..

Recommendations on definitions of the first stage of labor:  The first stage is further subdivided into the

latent and active phases. active phase subdivided into three additional

phases: 1. acceleration phase2. phase of maximum slope 3. deceleration phase

Recommendations on definitions of the first stage of labor:Latent phase is typically characterized by

mild, infrequent, irregular contractions with gradual change in cervical dilation (usually <1 cm / h) and effacement.

Nulliparous Multiparous

Latent phase 6.4 h 4.8 h

Abnormal 20 h 14 h

• Not influenced by maternal age, birth weight, or obstetric abnormalities

Recommendations on definitions of the first stage of labor:Active phase —  begins at 3 to 4 centimeters

when cervical dilatation is plotted against time..

characterized by painful contractions of increasing frequency, intensity, and duration accompanied by more rapid (usually >1 cm /h) cervical change.

Recommendations on definitions of the first stage of labor:

Recommendations on definitions of the first stage of labor:

Diagnosis of labor The determination of whether a woman is in labor is

made within one hour of admission . Diagnosis of labor is made only when painfull

contractions are accompanied by any one of the following :

Bloody show Rupture of the membranes Full cervical effacement. Cervical dilatation is not part of the criteria

Meet the criteria Labor unit

Didn’t meet the

criteria

Rest & observationUntil next

day

Discharge if labor hasn’t

begunAntinatal

ward

Diagnosis of labor

The correct diagnosis of labor is considered to be the single most important determination in the management of labor because an incorrect diagnosis of active labor will lead to inappropriate interventions and an increased likelihood of cesarean delivery.

Management on admissionPatient preparation — There is no evidence

that routine enemas or perineal shaving is beneficial .

A urinary catheter is not necessary unless the woman is unable to void, but she should be encouraged to empty her bladder regularly as a full bladder can impede fetal descent.

Fluids and oral intake — There is no consensus on acceptable maternal oral intake during uncomplicated labor

Management on admissionPlacement of an intravenous line or a

hep-lock at the time admission is recommended.

Interestingly, one randomized trial found that women who received intravenous hydration at 250 mL/h had fewer labors persisting for over 12 hours and less need for oxytocin augmentation than those who received 125 mL/h

Management on admissionAntibiotic prophylaxis  : (in some centers) to prevent early-onset neonatal infection in

appropriate patients; the agent of choice is intravenous penicillin.

A minimum of four hours of intrapartum therapy has been recommended prior to delivery

Although normal labor and vaginal delivery is not an indication for prophylaxis against infective endocarditis, some centers generally administer antibiotic prophylaxis during labor to pregnant women with underlying valvular heart disease.

Management on admissionMonitoring — All pregnant women require

surveillance (eg, monitoring of vital signs and FHR) since 20 to 25 % of all perinatal morbidity and mortality occurs in pregnancies with no underlying risk factors for adverse outcome .

Assessment of the quality of the uterine contractions and cervical examinations are repeated at appropriate intervals to follow the progress of labor.

Management on admissioncervical examination should be kept to a minimum to avoid promoting intraamniotic infection.

• On admission • At one to four hour intervals in the first stage and at one hour intervals in the second stage • At rupture of membranes to evaluate for cord prolapse • Prior to intrapartum administration of analgesia • When the parturient feels the urge to push to determine whether the cervix is fully dilated • If the FHR falls, to evaluate for conditions such as cord prolapse or uterine rupture.

In general, vaginal examinations are performed:

The results can be noted on a partogram

Management on admission

Active management of labor  It refers to active control, rather than passive

observation, over the course of labor by the obstetrical provider.

It includes three essential elements I. Careful diagnosis of labor by strict criteria II. Constant monitoring of labor with specific

standards for normal progression III. Prompt intervention (eg, amniotomy, high

dose oxytocin) according to established guidelines if progress is unsatisfactory .

Active management of laborThe active management of labor is generally

limited to women who meet the following criteria:

1) Nulliparous 2) Term pregnancy 3) Singleton infant in cephalic presentation 4) No pregnancy complications 5) Experiencing spontaneous onset of labor.

Active management of laborNulliparous labor tends to be more subject

to failure to progress . administration of oxytocin, sometimes at

high dosages, is one of the interventions involved in active management. This is safer in nulligravid women since the nulligravid uterus is virtually immune to rupture (except as a result of manipulation or previous surgery)

Active management of laborRecommendation on routine amniotomy

Limited evidence showed no substantial benefit for early amniotomy and routine use of oxytocin

compared with conservative management of labor.

In normally progressing labor, amniotomy should not be performed routinely.

Combined early amniotomy with use of oxytocin should not be used routinely.

Active management of labor

  Interventions with amniotomy and/or high dose oxytocin are initiated if progress does not proceed according to the defined standards.

Rutpure of the fetal membranes provides information about fetal status, but does not appear to significantly accelerate labor . In the Dublin protocol, rupture must be performed before treatment with oxytocin, which is administered only in the presence of clear amniotic fluid .

Active management of laborIf membranes are ruptured when there is

polyhydramnios or an unengaged fetal presenting part, it is prudent to use a small gauge needle, rather than a hook, to puncture the fetal membranes in one or more places, and to perform the procedure in the operating room. This "controlled amniotomy“ permits emergency cesarean delivery in the event of an umbilical cord prolapse .

Routine amniotomy should not be performed in women with active hepatitis B & C or HIV in order to minimize exposure of the fetus to ascending infection.

Active management of labor

So usually, Amniotomy is indicated to further evaluate fetal status (eg, placement of a fetal scalp electrode) or uterine contractions (eg, placement of an intrauterine pressure catheter).

Active management of labor

Slower progress in the nulliparous patient is most often the result of inefficient uterine action .

In the absence of medical contraindications, labor that fails to progress is treated with oxytocin

Monitoring It is desirable that all

examinations be performed by a single individual to minimize interobserver variations

A vaginal examination during labor often raises anxiety and interrupts the woman’s focus & if there is (PRoM), increasing numbers of VEs have been found to be associated with neonatal sepsis ….

Monitoring:Recommendations on monitoring during the

established first stage of labor

A pictorial record of labor (partogram) should be used once labor is established.

4 hourly temperature and blood pressure

hourly pulse

half-hourly documentation of frequency of contractions

frequency of emptying the bladder

vaginal examination offered 4 hourly, or when there is concern about progress

Intermittent auscultation of the fetal heart after a contraction should occur for at least

1 minute, at least every 15 minutes, and the rate should be recorded as an average.

Monitoring:Recommendations on initial monitoring:1) Psychological & Emotional2) Vitals & Urinalysis3) Uterine contractions4) Abdominal examination_Leopold manouvers5) Vaginal loss – show, liquor, blood6) Vaginal examination....when necessary7) Pain control8) FHR

Monitoring:

Explain

Monitoring: Fetal heart rate —  fetal heart rate assessment

has become a standard of care for all women in the United States because patients and clinicians are reassured by normal results and believe there is some value in detecting abnormal patterns.

Monitoring:The American College of Obstetricians and

Gynecologists suggests that electronic fetal monitoring tracings to be reviewed :

In general, continuous intrapartum FHR monitoring is suggested for high-risk patients and when FHR below 110 or over 160 BPM

First stage Second stage

Low risky 30 min 15 minHigh risky 15 min 5 min

Monitoring:Intermittent auscultation of the F.H is

recommended Once a woman is in established active labor,

intermittent auscultation of the fetal heart after a contraction should be continued

Intermittent auscultation can be undertaken by either Doppler ultrasound or Pinard stethoscope.

Monitoring:Uterine contractions 

i. simple observation of the motherii. palpation of the fundus iii. CTGiv. direct measurement of intrauterine

pressure via internal manometry or pressure transducers

95% of women in active labor will

have 3-5 contractions per 10 minutes.

Partogram:Maternal statusFetal heart rate Dilatation & descentUterine contractions

Partogram:a graphical representation that clearly shows the

patient's labor compared to the expected lower limit of "normal progress 

Some clinicians employ a partogram with alert and action lines. The alert line represents the rate of dilatation of the slowest 10 % of labors in primigravidae. Crossing the alert line suggests that the patient should be transferred to a hospital if she is laboring in a rural setting. The action line is parallel and four hours to the right of the alert line; crossing the action line suggests the need for intervention (eg, artificial rupture of the membranes, administration of oxytocics).

Abnormalities CervixUterusMaternal pelvis Fetus i.e ( power, passenger, or pelvis).

Hypocontractile uterine activity —  is the most common cause of protraction or arrest disorders in the first stage of labor. This entity refers to uterine activity that is either not sufficiently strong or not appropriately coordinated to dilate the cervix and expel the fetus. It occurs in 3-8 % of parturients and can be quantified as uterine contraction pressures less than 200 Montevideo units.

Abnormalities

Hypocontractile uterine activity is treated with oxytocin in the United States. Oxytocin is the only medication approved by the US Food and Drug Administration (FDA) for labor stimulation in the active phase

Abnormalities Active phase arrest is diagnosed when a

protraction disorder persists despite oxytocin therapy to achieve ≥ 200 Montevideo units for greater than two hours; cesarean delivery is typically performed at this point

The National Institute for Health and Clinical Excellence (NICE) also recommended starting oxytocin and monitoring the progress of labor over the next four hours. If less than 2 cm of cervical dilatation occurred, they recommended consideration of cesarean delivery

Abnormalities Cephalopelvic disproportion — A disproportion

between the size of the fetus relative to the mother can lead to a diagnosis of dystocia . This diagnosis is based upon observation of slow or arrested labor during the active phase. However, it is usually duo to fetal malposition (eg, extended or asynclitic fetal head) or malpresentation (mento- posterior, brow), rather than a true disparity between fetal and maternal pelvic dimensions

Abnormalities Diagnosis of POSITION can generally be

made by digital examination, but if there is uncertainty, ultrasound examination is useful and accurate

(OA)… (left 2/3)(Transverse positions are unstable)…(OP) …mostly spontaneously rotate to (OA)

during the course of labor. However, approximately 5 % experience

malposition with persistent OP position or transverse arrest.

Pain Control: The pain of childbirth is likely to be the most

severe pain that a woman experiences during her lifetime.

Pain Control: women should be involved in the decision of

pain relief, to increase maternal satisfaction.

This can be accomplished by educating women about pain relief techniques during pregnancy, prior to the onset of labor, as rational decision-making is difficult during times of emotional & physical stress .

Furthermore, using patient-controlled epidural analgesia (PCEA) empowers the parturient by giving her direct control of her pain relief, and this may increase maternal satisfaction .

Pain Control: First stage of labor   Visceral or cramp-like source : uterus and cervix, produced by distention of uterine

and cervical mechanoreceptors and by ischemia of uterine and cervical tissues///. The pain signal enters the spinal cord after traversing the T10, T11, T12, and L1 .

abdominal wall, lumbosacral region, iliac crests, gluteal areas, and thighs.///

Transition refers to the shift from the late first stage (7 to 10 cm cervical dilation) to the second stage of labor. Transition is associated with greater nociceptive input as the parturient begins to experience somatic pain from vaginal distention.

Pain Control: Hyperventilation —  consistently

accompanies labor pain. Arterial CO2 partial pressures less than 20 mmHg are not uncommon, and profound hypocarbia may inhibit ventilatory drive between contractions and result in maternal hypoxemia, lightheadedness, and loss of consciousness . respiratory alkalosis, which impairs oxygen transfer from the maternal to fetal circulation, may occur.

Pain Control: Psychological effects — unrelieved pain may

also be a factor that contributes to the development of postpartum psychological trauma. This may negatively influence the mother's postpartum adjustment, and in its most severe form, result in post-traumatic stress disorder (PTSD) which shouldn’t be underestemated.

ANALGESIA FOR THE FIRST STAGE OF LABOR :classified as either

systemic

locoregional

Systemic:IntravenousIntramuscularinhalation routes

most popular agents are opioids (eg, morphine, fentanyl, meperidine)

Systemic:Newer opioid analgesics — Fentanyl, a

synthetic opioid, and its congeners (eg, sufentanil, alfentanil, and remifentanil) have also been used to provide labor pain relief. These drugs have a short duration of action, so they are best administered using the intravenous, rather than the intramuscular route.

SystemicInhalation agents — Nitrous oxide . The

parturient self-administers the anesthetic gas using a hand-held face mask. The safety of this technique is that the parturient will be unable to hold the mask if she becomes too drowsy. A systematic review on nitric oxide for relief of labor pain concluded it was inexpensive, easy to administer, and safe for both mother and fetus. The analgesic effect was better than that produced by opioids, but less than with epidural analgesia

Regional techniques: Epidurals and Spinals are the most popular

modalities

Regional techniques are widely acknowledged to be the only consistently effective means of relieving the pain of labor and delivery. Local injection may also be administered to achieve paracervical or pudendal nerve block.

Pain control:Epidural analgesia provided better pain

relief than parenteral opioids. However, opioids were associated with a shorter duration of labor, less oxytocin augmentation, and fewer instrumental deliveries compared to epidural analgesia.

Side effects- epidural: Nausea, vomiting, and sedation & Respiratory depression which was the major neonatal concern

References:Up-to-DateClinical Guideline, September 2007,Funded to produce

guidelines for the NHS by NICERoyal College of Obstetricians and Gynaecologists: Clinical

Effectiveness Support Unit. The Care of Women Requesting Induced

Abortion. Evidence-based guideline No. 7. London: RCOGGovernment Statistical Service and Department of Health.

NHS Maternity Statistics, England: 2002–03. Statistical Bulletin 2004/10.

London: Department of Health; 2004. National Assembly for Wales. Maternity Statistics, Wales:

Methods of Delivery, No. SDR 40/2004. Cardiff: NationalAssembly for WalesNational Collaborating Centre for Women’s and Children’s

Health, Intrapartum care of healthy women and their babies dur ing childbirth