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Post-term Pregnancy - Surveillance Strategies. Dr. Yasir Katib MBBS, FRCSC, Perinatologist. Definitions. Post mature Post dates Post-term Prolonged . Definitions. Post term

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Post term pregnancy surveillance strategies

Post-term Pregnancy - Surveillance Strategies

Dr. Yasir Katib

MBBS, FRCSC, Perinatologist


Definitions
Definitions

  • Post mature

  • Post dates

  • Post-term

  • Prolonged


Definitions1
Definitions

Post term

  • Refers to a pregnancy that has extended to or beyond a gestational age of 42.0 weeks or 294 days from the first day of the LMP

  • Postterm pregnancy is associated with increased perinatal mortality and morbidity


Incidence
Incidence

Incidence

Depends upon the patient population

  • Percentage of primigravid women

  • Women with pregnancy complications

  • Ultrasound assessment of GA

  • Frequency of spontaneous preterm birth


Incidence1
Incidence

Incidence

  • In the United States, approximately 10% (range 3 to 14 percent) of all singleton pregnancies continue beyond 42 weeks of gestation

    WHO (1977), FIGO (1976)

  • 4% (2 to 7 percent) continue beyond 43 completed weeks in the absence of obstetric intervention


  • Definitions2
    Definitions

    • “Postdates” : the real issue is “post-what dates?”

    • “Post-term” or “prolonged” pregnancy are the preferred expressions for extended pregnancies


    Incidence2
    Incidence

    • limited reliability with LMP to determine accurate post-term incidence

      • variations in timing of ovulation

      • irregular cycles

      • use of oral contraceptives

    • when early ultrasound dating used in conjunction to LMP, incidence of post-term decreased from 10 % (LMP alone) to 3% (LMP + U/S) (Reuss et. al 1995)


    Etiology
    Etiology

    • The etiology of abnormal prolongation of gestation is not well understood (theories)

    • Hypoplasia of the fetal adrenal gland with or without anencephaly

    • Placental sulfatase deficiency

    • Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency


    Morbidity and mortality
    Morbidity and Mortality

    • Increase mortality > 42 weeks gestation

    • evidence from studies done looking outcome of post-term pregnancies prior to availability of intervention methods


    Perinatal mortality in late pregnancy according to gestational age in Sweden 1943-1952 compared with 1977-1978. Logarithm scale is used for convenience in depiction. (Adapted from Bakketeig and Bergsjø, 1991, and Lindell, 1956.)


    TABLE 3 OUTCOMES IN POSTTERM PREGNANCIES (42 WEEKS OR GREATER) COMPARED WITH PREGNANCIES DELIVERED AT 40 WEEKS

    40 Weeks Post-term

    (n = 8135) (n = 3457)

    Factor a (%) (%)

    Meconium 19 27

    Oxytocin induction 3 14

    Shoulder dystocia 8 18

    Cesarean delivery 0.7 1.3

    Macrosomia (> 4500 g) 0.8 2.8

    Meconium aspiration 0.6 1.6

    a For all comparisons between 40- and 42-week groups, P < 0.05.

    From Eden RD, Seifert LS, Winegar A, Spellacy WN. Perinatal characteristics of uncomplicated postdate pregnancies. Obstet Gynecol. 69:296, 1987.


    Macrosomia
    Macrosomia GREATER) COMPARED WITH PREGNANCIES DELIVERED AT 40 WEEKS

    • Complications associated with fetal macrosomia include

    • prolonged labor

    • cephalopelvic disproportion

    • shoulder dystocia with resultant risks of orthopedic (eg, clavicular fractures) or neurologic injury (eg, brachial plexus palsy)


    IUGR GREATER) COMPARED WITH PREGNANCIES DELIVERED AT 40 WEEKS

    • Poor intrauterine growth are at increased risk

    • Umbilical cord compression from oligohydramnios

    • Nonreassuring fetal antepartum or intrapartum assessment

    • Cesarean delivery


    Dysmaturity syndrome
    Dysmaturity syndrome GREATER) COMPARED WITH PREGNANCIES DELIVERED AT 40 WEEKS

    • Approximately 20%of postterm fetuses have a syndrome of fetal dysmaturity

    • long, thin, malnourished infant

    • Meconium staining

    • Peeling skin

    • Chronic intrauterine growth restriction from uteroplacental insufficiency


    Postmature infant delivered at 43 weeks’ gestation. Thick, viscous meconium coated the desquamating skin. Note the long, thin appearance and wrinkling of the palms of the hands.


    Induction vs surveillance
    Induction vs. Surveillance viscous meconium coated the desquamating skin. Note the long, thin appearance and wrinkling of the palms of the hands.

    • Several studies debate routine induction vs. surveillance

    • Hannah (1992)

      • Canadian trial showed routine induction reduced risk of perinatal death after 41 weeks, and not associated with increase risk of Caesarean section

      • cost analysis (Goeree 1995) showed induction less expensive than serial monitoring


    Induction vs surveillance1
    Induction vs.. Surveillance viscous meconium coated the desquamating skin. Note the long, thin appearance and wrinkling of the palms of the hands.

    • NICH 1994

      • American study showed that active labour induction was not associated with improved outcome when compared to expectant management (at 41 weeks)

    • thus either induction or expectant management acceptable


    Induction vs surveillance2
    Induction vs.. Surveillance viscous meconium coated the desquamating skin. Note the long, thin appearance and wrinkling of the palms of the hands.

    • No evidence to support elective induction or serial antenatal monitoring for uncomplicated pregnancy from 39-40 6/7 weeks


    Surveillance methods
    Surveillance Methods viscous meconium coated the desquamating skin. Note the long, thin appearance and wrinkling of the palms of the hands.

    • Biochemical markers

      • Plasma or urine estrogen

      • Human Placental Lactogen

      • Placental proteins

         no evidence to demonstrate benefit as antenatal surveillance for fetal well being in post-term pregnancies


    Surveillance methods1
    Surveillance Methods viscous meconium coated the desquamating skin. Note the long, thin appearance and wrinkling of the palms of the hands.

    • Non-invasive

      • Fetal movement counts

      • Non stress test (Cardiotocography)

      • Biophysical Profile

      • Amniotic Fluid Volume estimates

      • Doppler Ultrasound


    Surveillance methods2
    Surveillance Methods viscous meconium coated the desquamating skin. Note the long, thin appearance and wrinkling of the palms of the hands.

    • Others

      • Oxytocin challenge test / Contraction stress test

      • Amniocentesis

        • Knox et al (1979)

          • meconium detected by amniocentesis associated with intrapartum fetal distress; however induction of labour did not improve outcome


    Surveillance methods3
    Surveillance Methods viscous meconium coated the desquamating skin. Note the long, thin appearance and wrinkling of the palms of the hands.

    • NST

      • False-normal Non-stress Tests (Smith et al.1987)

        • fetal death within 7 days of normal non-stress tests

        • most common indication for testing was prolonged pregnancy

        • mean interval between test and death was 4 days, range of 1-7 days

        • single most common autopsy finding: meconium aspiration

        • investigators concluded that the non-stress test not adequate to preclude an acute asphyxial event

        • other biophysical characteristics might be beneficial adjuncts: For example, assessment of amniotic fluid volume

        • high false negative rates also reported by Miyazaki & Miyazaki (1981)


    Surveillance methods4
    Surveillance Methods viscous meconium coated the desquamating skin. Note the long, thin appearance and wrinkling of the palms of the hands.

    • Ultrasound assessment of amniotic fluid

      • increased incidence of fetal compromise with oligohydramnios in post-term pregnancies

      • identification of decreased amniotic fluid may identify post-term fetus in jeopardy


    Surveillance methods5
    Surveillance Methods viscous meconium coated the desquamating skin. Note the long, thin appearance and wrinkling of the palms of the hands.

    • Ultrasound Amniotic Fluid Estimates

      • qualitative (Crowley 1980)

        • presence of amniotic fluid between fetal trunk and limbs or uterine wall

      • quantitative

        • Largest single pocket method

        • Amniotic Fluid Index


    Amniotic fluid volume estimates
    Amniotic Fluid Volume Estimates viscous meconium coated the desquamating skin. Note the long, thin appearance and wrinkling of the palms of the hands.

    • Largest Pocket measurements

      • usually measured in the vertical

      • in BPP, a score of 2 is given for the presence of a 2x2 amniotic fluid pocket

      • studies of AFV estimation have had different lower limits ranging from 1-3cm (Manning 1980, Chamberlain 1984,Crowley 1984, Phelan 1985, Bochner 1987)


    Amniotic fluid volume estimate
    Amniotic Fluid Volume Estimate viscous meconium coated the desquamating skin. Note the long, thin appearance and wrinkling of the palms of the hands.

    • studies show that AFV may be effective discriminatory test in post-term pregnancy (Crowley 1984, Phelan 1985, Manning 1980)

    • normal AFV does not preclude absence of adverse outcome


    Amniotic fluid volume estimate1
    Amniotic Fluid Volume Estimate viscous meconium coated the desquamating skin. Note the long, thin appearance and wrinkling of the palms of the hands.

    • Amniotic Fluid Index

      • first proposed by Phelan (1986) and Rutherford et al (1987)

      • summation of vertical pockets in four quadrants

      • table of gestational age-dependent norm of AFI (Moore 1990); e.g. after 41weeks lower limit is 67 mm.


    Amniotic fluid volume estimate2
    Amniotic Fluid Volume Estimate viscous meconium coated the desquamating skin. Note the long, thin appearance and wrinkling of the palms of the hands.

    • AFV vs. AFI

      which is better???


    Doppler ultrasound
    Doppler ultrasound viscous meconium coated the desquamating skin. Note the long, thin appearance and wrinkling of the palms of the hands.

    • Fetal application first reported by Fitzgerald and Drumm (1977)

    • non-invasive technique that uses high-frequency sound to investigate blood flow by detecting change in frequency of reflected sound


    Doppler ultrasound1
    Doppler Ultrasound viscous meconium coated the desquamating skin. Note the long, thin appearance and wrinkling of the palms of the hands.

    • Theoretically, in post-term pregnancy:

      • increasing placental ‘age’ with increasing uteroplacental insufficiency

      • expect diminished uteroplacental flow, increased vascular resistance in umbilical artery and compensatory increased fetal cerebral artery flow (as in IUGR)


    Doppler ultrasound2
    Doppler Ultrasound viscous meconium coated the desquamating skin. Note the long, thin appearance and wrinkling of the palms of the hands.

    • Several small studies have reported conflicting results

    • positive studies usually small (Devine et al 1994, Anteby et al, 1994) or have strict criteria which are not common e.g. Absent end diastolic flow (Pearce et al, 1991)


    Doppler ultrasound3
    Doppler Ultrasound viscous meconium coated the desquamating skin. Note the long, thin appearance and wrinkling of the palms of the hands.

    • Negative studies show poor discrimination of potential fetal compromise (Guidetti 1987, Farmakides 1988)

    • Zimmerman et al (1995) showed that Doppler of uterine artery had a sensitivity of 7% in predicting poor outcome


    Doppler ultrasound4
    Doppler Ultrasound viscous meconium coated the desquamating skin. Note the long, thin appearance and wrinkling of the palms of the hands.

    • Thompson and Trudinger 1990:

      • Observations using placenta and mathematical models

      • the larger the placenta (and its arterial branches), the greater fraction of vessels need to be obliterated before RI becomes abnormal

      • this may explain poor sensitivity of umbilical Doppler in post-term pregnancies


    Clinical practice guidelines
    Clinical Practice Guidelines viscous meconium coated the desquamating skin. Note the long, thin appearance and wrinkling of the palms of the hands.

    • ACOG Practice Patterns (1997)

      • “Due to ethical and medico-legal concerns, it is highly unlikely that any subsequent studies will include a no-monitoring group”

      • “…antenatal surveillance has become a standard practice on the basis of universal acceptance”


    Clinical practice guidelines1
    Clinical Practice Guidelines viscous meconium coated the desquamating skin. Note the long, thin appearance and wrinkling of the palms of the hands.

    • ACOG Practice Patterns (1997)

      • Antenatal surveillance should be initiated by 42 weeks of gestation (C:III)

      • No single antenatal surveillance protocol for monitoring fetal well-being in a post-term pregnancy appears superior to another


    Clinical practice guidelines2
    Clinical Practice Guidelines viscous meconium coated the desquamating skin. Note the long, thin appearance and wrinkling of the palms of the hands.

    • SOGC Committee Opinion (1997)

      1. Establish gestational age

      2. For uncomplicated pregnancy, no evidence to support elective induction or commencement of serial antenatal monitoring at 39 to 40 6/7 weeks


    Clinical practice guidelines3
    Clinical Practice Guidelines viscous meconium coated the desquamating skin. Note the long, thin appearance and wrinkling of the palms of the hands.

    • SOGC Committee Opinion (1997):

      3. Women who reach 41 to 42 weeks of gestation (uncomplicated pregnancies) should be offered elective delivery

      4. Serial fetal surveillance should consist (as a minimum) of an ultrasound assessment of amniotic fluid volume twice weekly…other forms of monitoring may be added to this (BPP, NST and fetal movement count)


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