Postterm PregnancySurveillance Strategies

1、post-term pregnancy - surveillance strategies dr. yasir katib mbbs, frcsc, perinatologist definitions post mature post dates post-term prolonged definitions 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 pregnan

2、cy is associated with increased perinatal mortality and morbidity incidence incidence depends upon the patient population 1.percentage of primigravid women 2.women with pregnancy complications 3.ultrasound assessment of ga 4.frequency of spontaneous preterm birth incidence incidence in the united st

3、ates, 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 definitions “postdates” : the real issue is “post-what dates?” “p

4、ost-term” or “prolonged” pregnancy are the preferred expressions for extended pregnancies 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

5、 lmp, incidence of post-term decreased 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) 1.hypoplasia of the fetal adrenal gland with or without anencephaly 2.placental sulfatase deficiency 3.cong

6、enital adrenal hyperplasia (cah) due to 21-hydroxylase deficiency 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 gestati

7、onal age in sweden 1943-1952 compared with 1977-1978. logarithm scale is used for convenience in depiction. (adapted from bakketeig and bergsj, 1991, and lindell, 1956.) table 1 perinatal deaths, excluding infants with malformations, in singleton births at 40, 41, and 42 weeks at parkland hospital,

8、1993 1994 gestational age outcomea40 wks41 wks42 wks pregnancies708949953582 inductions (%)317 (5)301 (6)865 (24) stillbirths853 neonatal deaths002b perinatal deaths8 (1.1)5 (1.0)5 (1.4) (per 1000) a includes women without prenatal care. b one neonatal death due to group b streptococcal sepsis. tabl

9、e 3 outcomes in postterm pregnancies (42 weeks or greater) compared with pregnancies delivered at 40 weeks 40 weekspost-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

10、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 complications associated with fetal macrosomia include 1.prolonged labor 2

11、.cephalopelvic disproportion 3.shoulder dystocia with resultant risks of orthopedic (eg, clavicular fractures) or neurologic injury (eg, brachial plexus palsy) iugr poor intrauterine growth are at increased risk 1.umbilical cord compression from oligohydramnios 2.nonreassuring fetal antepartum or in

12、trapartum assessment 3.cesarean delivery dysmaturity syndrome approximately 20%of postterm fetuses have a syndrome of fetal dysmaturity 1.long, thin, malnourished infant 2.meconium staining 3.peeling skin 4.chronic intrauterine growth restriction from uteroplacental insufficiency postmature infant d

13、elivered 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. surveillance hannah (1992) canadian trial showed routine induction red

14、uced 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. surveillance nich 1994 american study showed that active labour induction was not associated with i

15、mproved 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 6/7 weeks surveillance methods bioch

16、emical 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 methods non-invasive fetal movement counts non stress test (cardiotocography) biophysical profil

17、e amniotic fluid volume estimates doppler ultrasound surveillance methods 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 survei

18、llance 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 days single most common autopsy finding: meconium aspirati

19、on 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 e.g. after 41weeks lower limit is

20、 67 mm. amniotic fluid volume estimate afv vs. afi which 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 ultrasou

21、nd 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

22、 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 ultrasound negative studies show poor discrimination of potential fetal compromis

23、e (guidetti 1987, 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),

24、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 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 guidelines acog practice patter