UTHSCSA Family & Community Medicine Dept.


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Active Labor: diagnosed in the presence of regular, painful contractions plus at least on of the following elements:  

    • Complete effacement of the cervix
    • Progressive cervical change
    • Bloody Show
    • Ruptured membranes
  • Make sure all consents are signed and info on H/P is correct and complete
  • Vaginal exams Q1h on active laboring patients >4cm
  • Check position of head at least by 7-8 cm if possible
Stages of Labor
First Stage
Time from the onset of labor until complete cervical dilation
Second Stage
Time from complete cervical dilation to expulsion of the fetus
Third Stage
Time from explusion of the fetus to expulsion of the placenta

2 phases:

  1. Latent Phase: characterized by mild, infrequent, irregular contractions with gradual change in cervical dilation (usually <1cm per hour) and effacement. The average duration of latent phase in nulliparous and multiparous women is 6.4 and 4.8 hours, respectively. An abnormally long latent phase is defined as 20 hours for the nullipara and 14 hours for the multiparous woman.
  2. Active Phase: rapid change in the rate (slope) of cervical dilation occurs at 3 to 4 centimeters. Average duration of active labor (onset defined as 3cm dilation) in nulliparous and parous women was 6.4 and 4.6 hours, respectively.

The median duration nulliparous and multiparous women is 50 and 20 minutes, respectively. The upper limit of duration associated with a normal perinatal outcome had been defined as two hours, but was subsequently lengthened when the length of the second stage was shown not to be an independent risk factor for neonatal morbidity.


The length of the third stage itself is usually 15-30 minutes. The time may be up to 60 minutes in some cases. Do not pull on the cord with excessive force because this may result in an inverted uterus – an obstetrical emergency with significant morbidity.

Abnormal Labor
Abnormal labor of the second stage is often a result of problems with one of the 3 P's.  [from eMedicine]

  1. Passenger (infant size and fetal presentation, eg, in cephalic-occiput anterior or occiput posterior vs breech or transverse)
    • Passenger, may produce abnormal labor because of the infant's size (eg, macrosomia) or from malpresentation such as OP
  2. Pelvis or passage (size and adequacy of the pelvis)
    • Pelvis, can cause abnormal labor because its contours may be too small or narrow to allow passage of the infant. Both the passenger and pelvis cause abnormal labor by a mechanical obstruction, referred to as dystocia. *Note: A patient who is extremely short or very obese is at increased risk of abnormal labor.
  3. Power (uterine contractility)
    • Power, the frequency of uterine contraction may be adequate, but the intensity may be inadequate. An arrest disorder cannot be diagnosed until the patient is in the active phase and the contraction pattern exceeds 200 MVUs for 2 hours with no cervical change.
Diagnostic Criteria for Abnormal Patterns in Active Labor*
First Stage Labor Nullipara Multipara
Abnormal duration >24.7 hours >18.8 hours
Protracted dilation <1.2 cm/hr <1.5 cm/hr
Arrest of dilation >2 hours >2 hours
Second Stage of Labor
Arrest of descent (epidural) >3 hours >2 hours
Arrest of descent ( no epidural) >2 hours >1 hour
Note: Pitocin has a half-life of 3-5 minutes, and reaches steady state in approximately 40 minutes.
*Source: UpToDate.

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GBS Prophylaxis

GBS Prophylaxis:  needs at least 2 doses to be adequate

    • GBS Pos - Ampicillin 2g IV load then 1g Q4°
    • GBS Neg- no prophylaxis  regardless of duration of labor or ROM
    • GBS Unknown (>36 weeks) - Start above prophylaxis only if ROM >18h or temp>100.0
    • Pre Term Labor: Start above prophylaxis upon diagnosis of labor. Continue until GBS known to be neg (within the last 2 weeks).
    • PPROM: start prophylaxis above
      • if GBS+, continue abx’s and repeat GBS Q3-4 days until negative,  restart prophylaxis when pt goes into labor
      • if GBS -, stop abx prophylaxis, restart abx if labor reoccurs <36 weeks and the most recent  negative GBS cx was >2 weeks ago. Repeat culture @ 35-37wks

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Diagnosis of Preeclampsia:

    • Elevated BP >/=140 Systolic OR 90 Diastolic AND 1+ protein
    • or elevated BP with > 300mg in 24 h urine
    • minimal if any LFT elevation and no other problems

Diagnosis of Severe Preeclampsia

    • >/= 160 Sys OR 110 Diastolic on two separate occasions > 6h apart,
    • persistent 2+ or >/= 3+ proteinuria
    • + scotomata, RUQ/Mid epigastric pain, persistent frontal headache,
    • Oliguria <30ml/h
    • LFTs 2x elevated, Plts <100K, elevated creatinine
    • pulmonary edema
    • IU growth restriction
    • oligohydramnios

Treatment of Preeclampsia:

  • Magnesium Sulfate - 4g bolus, then 2g/hr
  • Hydralazine - if >160/110, then 5mg IV, increase to 10mg IV if no response, if no response give another 10mg IV – if still no response – then change med.
  • Labetolol - 20 mg IV, then 40mg, then 80mg, then 160mg (up to q10min) – max 300mg
    • Tox Check:  (MAGNESIUM TOXICITY – turn off mag, give oxygen, and Ca Gluconate 10 ml of 10% Solution IV (1g IV)

        Magnesium effects:

        <7 - decreased reflexes
        7-8 - loss of ocular reflex/blurry vision
        10 - respiratory depression
        15 - cardiac abnormalities

    • Tox Check Note:

      S:  Presence of HA/Visual changes/RUQ pain/SOB
      O:  VS:  O2 sat, BP ranges (< 150/90 okay), urine output (< 30ml/hr is bad) Heart/Lungs/Abd/Ext/DTRs:
      Labs:  Magnesium level (LFTs, Uric Acid, U/A, CBC, SMA 7 if recently done or previous abnormal)
      A/P:  ___ yo G __ P ___ s/p SVD/LTCS with GHTN or mild/severe preeclampsia with good BPs and good UOP.  No s/sxs of worsening disease. Continue Magnesium and Tox checks q 6° until 12°/24° after delivery.  Continue postpartum care.

    • Transfer Note to Ward after cleared of PIH

      Discontinue Magnesium SULFATE
      Discontinue Foley
      Write out orders (cannot write “resume PP orders”)
      Transfer to Ward – SVD or OB Comp A/B

    • Severe Pre Eclampsia:  Tox checks Q6h, Magnesium levels Q6h

      Flow sheet:  BP, I/O, Meds, Magnesium, Urine protein, H/H, Plts,
      BUN/Cr, AST/ALT, Total bilirubin/Uric Acid

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  • Mg Sulfate 4g IV bolus (over 15 min), then 2g per hour
  • may give IV push as 20% solution - will burn (push max of 1g/min)
    (may have transient fetal bradycardia, stabilize mom and usually baby will resuscitate in 20-30 min)
  • If don't have IV, give Mg Sulfate 4g IM in each buttock

Non Reassuring Strip:

  • Oxygen, Pt on side
  • Pitocin off
  • Blood pressure adequate
  • Cervical exam with scalp stimulation
  • Consider internals
  • Call Chief, VAS

Postpartum hemorrhage PPH:

  • Fundal massage
  • Call OB
  • Place Foley or I&O cath
  • Check for retained products, Pitocin running?
  • Methergine 0.2mg IM Q15 min. (if no HTN)
  • Hemabate 250 mcg IM (if no ASTHMA)
  • Check for lacerations
  • Misoprostol 1000 mcg rectally
  • Consider DIC panel
  • Hang red top of blood-observer clotting time
    • EBL
      Average EBL for NSVD is 500cc
      Average EBL for C/S is 1000cc
      One unit of whole blood is 500cc
      PRBC 335cc
      Blue basin for placenta = 3.5 liters
      Average adult human has 10 liters of blood

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TETANY: turn off Pitocin, give oxygen, left side - Terbutaline 0.25 mg SQ or 1/2 SQ, 1/2 IV.


Cervidil: 10mg placed in cervix then remove after 12h, start pit one hour after removal.

Misoprostol: wet medication, no gel, 25mcg (1/4 of a 100 mcg tab), place in post fornix Q4-6hrs, remove any undissolved pills, no oxytocin until 4h after last dose.

Inclusion Criteria: singleton, cephalic, bishop <6, <=2 ctx's/10 min, reactive NST

Pitocin dosing for induction or augmentation of labor:

  • Low dose (Start with 2 mu/min and go up by 2 mu/min) – for grand multips/VBAC's.
  • Higher dose (4 – 6 mu/min and go up by 4 mu/min) –  for nullips or those not responding well.

If IUPC then use a goal of 200 - 300 Montevideo units (MVU). The mean force to initiate cervical change is 275 MVU (Montevideo units)

Calculation of Montevideo units (MVU)
(the peak strength of contractions in mmHg measured by an internal monitor multiplied by their frequency per 10 minutes)

Measure the peak amplitude of each contraction = A in mm Hg
Count the number of contractions in 10 minutes = N
MVU = A x N
(Example: contractions of 60 mm Hg with 4 in 10 minutes = MVU of 240

In a retrospective report, 91 percent of women in spontaneous active labor achieved contractile activity greater than 200 Montevideo units and 40 percent reached 300 Montevideo units. [UpToDate]


24-32 weeks
Goal: To allow 48 hours of steroids (Dexamethasone or Betamethasone)
Magnesium: 6g IV load over 20 min, then 3g IV/h, (Goal 6-8 Mag level). Reversal of effects with Calcium Gluconate 1g IV.
Sulindac: 200mg po q 12h x 48h
Terbutaline: 0.25mg SC q 30min up to 1mg in 4hrs (not at UH very often)

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