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1、Post-term Pregnancy-Surveillance Strategies,Dr.Yasir Katib MBBS,FRCSC,Perinatologist,Definitions,Post maturePost datesPost-termProlonged,Definitions,Post termRefers 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 pregna
2、ncy is associated with increased perinatal mortality and morbidity,Incidence,Incidence Depends upon the patient populationPercentage of primigravid womenWomen with pregnancy complicationsUltrasound assessment of GA Frequency of spontaneous preterm birth,Incidence,Incidence In the United States,appro
3、ximately 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,Definitions,“Postdates”:the real issue is“post-what dates?”“Post-term”or“prolonged”p
4、regnancy are the preferred expressions for extended pregnancies,Incidence,limited reliability with LMP to determine accurate post-term incidencevariations in timing of ovulationirregular cyclesuse of oral contraceptiveswhen early ultrasound dating used in conjunction to LMP,incidence of post-term de
5、creased from 10%(LMP alone)to 3%(LMP+U/S)(Reuss et.al 1995),Etiology,The etiology of abnormal prolongation of gestation is not well understood(theories)Hypoplasia of the fetal adrenal gland with or without anencephalyPlacental sulfatase deficiency Congenital adrenal hyperplasia(CAH)due to 21-hydroxy
6、lase deficiency,Morbidity and Mortality,Increase mortality 42 weeks gestationevidence 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 1977-197
7、8.Logarithm scale is used for convenience in depiction.(Adapted from Bakketeig and Bergsj,1991,and Lindell,1956.),TABLE 3 OUTCOMES IN POSTTERM PREGNANCIES(42 WEEKS OR GREATER)COMPARED WITH PREGNANCIES DELIVERED AT 40 WEEKS40 WeeksPost-term(n=8135)(n=3457)Factor a(%)(%)Meconium 19 27Oxytocin inductio
8、n 3 14Shoulder dystocia 8 18Cesarean delivery 0.7 1.3Macrosomia(4500 g)0.8 2.8Meconium aspiration 0.6 1.6a 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
9、.,Macrosomia,Complications associated with fetal macrosomia include prolonged laborcephalopelvic disproportionshoulder dystocia with resultant risks of orthopedic(eg,clavicular fractures)or neurologic injury(eg,brachial plexus palsy),IUGR,Poor intrauterine growth are at increased riskUmbilical cord
10、compression from oligohydramnios Nonreassuring fetal antepartum or intrapartum assessmentCesarean delivery,Dysmaturity syndrome,Approximately 20%of postterm fetuses have a syndrome of fetal dysmaturitylong,thin,malnourished infantMeconium staining Peeling skinChronic intrauterine growth restriction
11、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,Several studies debate routine induction vs.surveillanceHannah(1992
12、)Canadian trial showed routine induction reduced risk of perinatal death after 41 weeks,and not associated with increase risk of Caesarean sectioncost analysis(Goeree 1995)showed induction less expensive than serial monitoring,Induction vs.Surveillance,NICH 1994American study showed that active labo
13、ur induction was not associated with improved outcome when compared to expectant management(at 41 weeks)thus either induction or expectant management acceptable,Induction vs.Surveillance,No evidence to support elective induction or serial antenatal monitoring for uncomplicated pregnancy from 39-40 6
14、/7 weeks,Surveillance Methods,Biochemical markersPlasma or urine estrogenHuman Placental LactogenPlacental proteins no evidence to demonstrate benefit as antenatal surveillance for fetal well being in post-term pregnancies,Surveillance Methods,Non-invasiveFetal movement countsNon stress test(Cardiot
15、ocography)Biophysical Profile Amniotic Fluid Volume estimatesDoppler Ultrasound,Surveillance Methods,OthersOxytocin challenge test/Contraction stress testAmniocentesis Knox et al(1979)meconium detected by amniocentesis associated with intrapartum fetal distress;however induction of labour did not im
16、prove outcome,Surveillance Methods,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 dayssingle most common autopsy finding:me
17、conium aspiration investigators concluded that the non-stress test not adequate to preclude an acute asphyxial eventother biophysical characteristics might be beneficial adjuncts:For example,assessment of amniotic fluid volume high false negative rates also reported by Miyazaki&Miyazaki(1981),Survei
18、llance Methods,Ultrasound assessment of amniotic fluidincreased incidence of fetal compromise with oligohydramnios in post-term pregnanciesidentification of decreased amniotic fluid may identify post-term fetus in jeopardy,Surveillance Methods,Ultrasound Amniotic Fluid Estimatesqualitative(Crowley 1
19、980)presence of amniotic fluid between fetal trunk and limbs or uterine wallquantitativeLargest single pocket methodAmniotic Fluid Index,Amniotic Fluid Volume Estimates,Largest Pocket measurementsusually measured in the verticalin BPP,a score of 2 is given for the presence of a 2x2 amniotic fluid po
20、cketstudies 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,studies show that AFV may be effective discriminatory test in post-term pregnancy(Crowley 1984,Phelan 1985,Manning 1980
21、)normal AFV does not preclude absence of adverse outcome,Amniotic Fluid Volume Estimate,Amniotic Fluid Indexfirst proposed by Phelan(1986)and Rutherford et al(1987)summation of vertical pockets in four quadrantstable of gestational age-dependent norm of AFI(Moore 1990);e.g.after 41weeks lower limit
22、is 67 mm.,Amniotic Fluid Volume Estimate,AFV vs.AFIwhich is better?,Doppler ultrasound,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 Ultrasound,
23、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 Ultrasound,Several small studie
24、s have reported conflicting resultspositive 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 Ultrasound,Negative studies show poor discrimination of potential fetal compromise(Guidetti 1987
25、,Farmakides 1988)Zimmerman et al(1995)showed that Doppler of uterine artery had a sensitivity of 7%in predicting poor outcome,Doppler Ultrasound,Thompson and Trudinger 1990:Observations using placenta and mathematical models the larger the placenta(and its arterial branches),the greater fraction of
26、vessels need to be obliterated before RI becomes abnormalthis may explain poor sensitivity of umbilical Doppler in post-term pregnancies,Clinical Practice Guidelines,ACOG Practice Patterns(1997)“Due to ethical and medico-legal concerns,it is highly unlikely that any subsequent studies will include a
27、 no-monitoring group”“antenatal surveillance has become a standard practice on the basis of universal acceptance”,Clinical Practice Guidelines,ACOG Practice Patterns(1997)Antenatal surveillance should be initiated by 42 weeks of gestation(C:III)No single antenatal surveillance protocol for monitorin
28、g fetal well-being in a post-term pregnancy appears superior to another,Clinical Practice Guidelines,SOGC Committee Opinion(1997)1.Establish gestational age2.For uncomplicated pregnancy,no evidence to support elective induction or commencement of serial antenatal monitoring at 39 to 40 6/7 weeks,Cli
29、nical Practice Guidelines,SOGC Committee Opinion(1997):3.Women who reach 41 to 42 weeks of gestation(uncomplicated pregnancies)should be offered elective delivery4.Serial fetal surveillance should consist(as a minimum)of an ultrasound assessment of amniotic fluid volume twice weeklyother forms of monitoring may be added to this(BPP,NST and fetal movement count),
