Multiple Gestation (2005) Implications of Chorionicity Ultrasonography of Nuchal Cords

1
Multiple Gestation (2005)Implications of
ChorionicityUltrasonography of Nuchal Cords

• David M. Sherer, MD
• Professor of Obstetrics and Gynecology
• State University of New York (SUNY),
• Downstate Medical Center
• Brooklyn, NY

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Multiple Gestations (2005)Implications of
Chorionicity
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Twin Gestation

• Marked recent increase in the incidence of
  twinning and other high-order multiple gestations
  reflects impact of ART
• Current incidence 140 deliveries
• Approximately 50 of twin gestations currently
  result from infertility treatment.
• Increased representation of older patients
  already at increased risk for adverse perinatal
  outcome

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Twin Gestation

• Significantly increased perinatal morbidity and
  mortality rates in comparison with singleton
  gestations.
• Perinatal mortality rate 3-7 fold higher than
  among singletons.
• While accounting for only 2.5 of the population,
  twins account for 12.6 of all perinatal
  morbidity.

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Twin Gestation

• Monozygotic twinning constant across populations
• 1 in 250 births
• independent of maternal age and parity
• Dizygotic twinning rates vary between
• 1 in 20 and 1 in 500 births
• rates vary with maternal age, parity, genetic
  factors and ART
• It is estimated that 20 of all twins are
  monochorionic and 80 are dichorionic
• Monozygotic and monochorionic twins are
  associated with a relatively high incidence of
  perinatal morbidity and mortality

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Increased Morbidity Mortality

• Preterm birth
• Fetal growth restriction
• Low birthweight
• Congenital anomalies

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Increased Morbidity Mortality

• Problems unique to twin gestations
• Twin Twin Transfusion, Twin Reverse Arterial
  Perfusion, Conjoined Twins, Cord Entanglement
• Twofold increase in spontaneous abortion
• Birth trauma
• Overall increase in maternal complications
  (preeclampsia, pregnancy-induced hypertension,
  gestational diabetes, placental abruption,
  placenta previa, both ante and postpartum
  hemorrhage)

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Twin GestationMorbidity and Mortality

• Perinatal mortality rate for monozygotic twins is
  approximately 3 fold higher than for dizygotic
  twins

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Twin GestationMorbidity and Mortality

• Mortality in monochorionic twin gestations is
  almost twice as high as dichorionic twin
  gestations (and fourfold higher than singletons)
• (Machin G, et al Am J Med Genet 19955571-6)

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Hidden Mortality of Monochorionic Twin
Gestations

• Data from nuchal translucency screening of 102
  monochorionic and 365 dichorionic twins
• Higher rate of fetal loss prior to 24 weeks
  gestation (12.2 vs.1.8)
• Perinatal mortality lt 32 wks (2.8 vs. 1.6)
• Prevalence of preterm delivery (9.2 vs. 5.5)
• Prevalence of birthweight lt 5th centile in both
  twins (7.5 vs. 1.7)
• While overall, MC twins sustained a 3 fold
  increase in loss of both twins in comparison with
  DC twins, the proportion of birthweight
  discordancy gt 25 was similar (11.3 vs.12.1)
• (Sebire et al. BJOG 19971041203-7)

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TVS depiction of chorionic and amniotic type at lt
14 wks

• 212 multifetal gestations scanned lt 14 wks
• Number of fetuses and chorionic and amniotic were
  determined ultrasonographically
• Of 212, 54 delivered in the authors institution,
  and of these 43 had pathology assessment of the
  placenta (40 twins and 3 sets of triplets)
• All US membrane assessments were precise
• Conclusion TVS US lt 14 wks accurately depict
  chorion and amnion type in multifetal pregnancies
• (Monteagudo A et al AJOG 1994170824-9)

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Chorionicity and Perinatal Outcome

• Perinatal morbidity and mortality differ among
  twin gestations of varying membrane and placental
  arrangements
• Compared with dichorionic twins, monchorionic
  twins exhibit a 3-5 fold higher incidence of
  perinatal morbidity and mortality
• (Bajora R, Kingdom J. Prenat Diagn 1997171207)

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Chorionicity and Perinatal Outcome

• Prospectively assessed outcomes of 68 twin
  gestations diagnosed in the first-trimester with
  two active fetal hearts as a function of
  chorionicity,
• The outcome of dichorionic twin gestations was
  significantly better than monochorionic twins
  (83 vs. 56 delivered twins, 12 vs. 11
  delivered singletons and 5 vs. 33 none,
  respectively)
• Interestingly among dichorionic twins, pregnancy
  outcome was less favorable when diagnosed between
  6 -8 weeks vs. 8-13 weeks
• (Benson C. Ultrasound Obstet Gynecol
  19933343-5)

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Chorionicity and PerinatalOutcome

• Retrospective cohort study of 44 MC and 164 DC
  twin gestations followed gt 20 weeks assessed the
  effect of chorionicity on infant outcome at 1
  year of age
• Adverse outcomes (death, cerebral palsy and
  mental retardation) occurred in 10 (9/88) of MC
  vs. 3.7 (12/328) DC infants.
• Delivery did occur on average 1 week earlier
  (34.72.8 vs 35.7 2.3) in MC vs. DC twins
• (Minakami et al. J Reprod Med 199944595-600)

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Chorionicity PerinatalOutcome

• However, no significant difference in GA at birth
  or birthweight were noted between 9 MC and 12 DC
  infants with adverse outcomes
• TTT was considered etiology of adverse outcome in
  7 MC infants
• All nine MC and 33 (4/12) DC infants with
  adverse outcomes belonged to twin pairs that had
  birthweight discordancies
• 25
• (Minakami et al. J Reprod Med 199944595-600)

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Fetal Death of One Twin

• Antepartum death of a single fetus complicates
  between 2.5 and 5 of all twin gestations and is
  associated with significant morbidity and
  mortality in the survivor

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Fetal Death of One Twin

• Intrauterine fetal demise of one of the twins is
  3-4 times more common in monochorionic twins, yet
  by no means unique to MC gestations
• Carlson and Towers reported 17 cases of a fetal
  death among 642 multiple gestations
• No major morbidity or mortality occurred among
  survivors of dichorionic twins
• (Carlson and Towers, Obstet Gynecol 198973685-9)

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Fetal Death of One Twin

• Compared outcomes between 50 MC vs. 42 DC twin
  gestations with one fetal demise
• Among MC twins, the incidence of fetal demise of
  the co-twin (13/50 vs. 1/42) and total perinatal
  mortality rate (29/50 vs. 9/42) were higher in
  the MC group
• Among MC group anemia was noted in 19/37 of the
  surviving co-twins
• (Bajora et al. Hum Reprod 1999142124-300)

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Twin Gestation

• Fetal testing of twins includes
• Fetal movement assessment
• Nonstress testing
• Biophysical profile
• Doppler velocimetry
• US (interval fetal growth)
• The above surveillance methods have not been
  assessed prospectively (randomized or sratified
  according to chorionicity)

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Twin Gestation

• Assessed 37 patients with twins who received care
  prior to 32 weeks with25 patients with no care/or
  presented gt32 weeks
• Statistically significant differences were noted
  in the perinatal mortality rate of monitored
  (68/1000) vs. non-monitored patients (160/1000).
• Significant differences were observed in mean
  birthweights (2645 g vs. 2007 g, respectively)
• (Gardner et al, J Reprod Med 199035519-21)

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Twin Gestation

• Randomized 8662 women to receive (or not receive)
  routine US screening
• All twins were detected in the US group vs. 76.3
  of controls.
• Perinatal mortality was 27.8/1000 vs. 65.8/1000
  among controls
• (Helsinki Ultrasound Trial, Saari Kempainen et
  al, Lancet 1990336387-91)

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Summary

• A marked lack of objective evidence-based data
  are available as to the precise preferred
  surveillance modalities and recommended intervals
  between testing of twins in general, irrespective
  of chorionicity.

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Summary

• It appears reasonable to maintain that
• The DC twin gestation represents a high-risk
  pregnancy
• The MC-DA twin gestation represents a very
  high-risk pregnancy
• The MC-MA twin gestation represents an extremely
  high-risk pregnancy

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Summary

• Early prenatal knowledge of chorionicity is
  important
• Nevertheless, at least until definitive
  (prospective randomized) data become available,
  DC twin gestations should not be exempted from
  increased fetal surveillance applied to twins
• Twins should be followed routinely with interval
  US growth assessments (3-4 week intervals)
• Targeted surveillance of MC twins may be
  implemented at critical (early) gestational ages

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Prenatal Ultrasonographic Diagnosis of Nuchal
Cords
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Pathogenesis of Nuchal Cords

• Unclear.
• It appears that fetal movements may result in the
  formation of nuchal cords.
• Excessive fetal movement and long umbilical cords
  - are prone to entanglement.
• Does not explain why some fetuses develop nuchal
  cords and others do not.

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Incidence of Nuchal Cords

• Frequency of nuchal cords increases with
  advancing gestational age (from 5.8 to 29.0
  between 20 and 42 weeks gestation,
  respectively).
• Ranges between 15.8 and 30.
• Single, double, triple, quadruple loops at
  10.6, 2.5, 0.5 and 0.1, respectively (Br J
  1957).
• Single, double, triple loops at 21.7, 1.7, and
  0.3 (J Fam Prac 1992).
• Nuchal cords may reduce spontaneously.

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Perinatal Outcome (1)

• Unclear whether or not nuchal cords are
  associated with increased adverse perinatal
  outcome.
• Associated with neonatal shock and anemia.
• Increased incidence of intrapartum fetal
  distress.

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Perinatal Outcome (2)

• Fetuses with nuchal cords were associated with a
  significantly increased prevalence of variable
  decelerations of the FHR versus matched controls
  in both the first and second stages of labor.
• Umbilical artery pH, 7.25 vs. 7.27 (Plt.05).
• Umbilical artery acidemia usually mixed (68) or
  respiratory in origin (23).
• Metabolic acidemia was infrequent (9).
• (Hankins GV et al, Obstet Gynecol
  198770687-91).

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Perinatal Outcome (3)

• Retrospective, case control study of 167 infants
  with nuchal cords vs. 523 controls.
• Fetal bradycardia and variable decelerations
  occurred significant more often in the nuchal
  cord group (18.6 vs. 9.6).
• No significant differences in operative
  deliveries or 1, 5 minute Apgar scores.
• Neonates with nuchal cords weighed significantly
  less than controls.
• (Miser et al, J Fam Prac 199234441-4)

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Perinatal Outcome (4)

• Compared with single or no cord entanglement,
  pregnancies with multiple nuchal cords were more
  likely to have
• Meconium-stained amniotic fluid
• Intrapartum fetal heart rate changes
• Operative vaginal delivery
• Low 1 minute Apgar scores
• Mild umbilical artery acidosis at birth
• (Larson et al, Am J Obstet Gynecol
  19951731228-31)

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Perinatal Outcome (5)

• Among 70 women delivering infants with nuchal
  cords, there were significantly increased
  incidences of
• Meconium-stained amniotic fluid
• Severe intrapartum variable decelerations
• Fetal bradycardia
• These authors suggested that in the presence of
  oligohydramnios, nuchal cord might represent an
  increased risk of intrapartum FHR changes.
• (Strong et al, J Reprod Med 199237718-20)

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Perinatal Outcome (6)

• Although it is extremely difficult to prove
  causality, nuchal cord(s) have been implemented
  in occurrences of intrauterine fetal death.

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Previous Diagnostic Modalities

• Spontaneous testing
• Increased incidence of variable FHR decelerations
  (3 episodes, 15 bpm, lasting 15 sec).
• Double or W pattern of FHR.
• Evoked testing
• Recording FHR following manual transabdominal
  compression of fetal neck (82.3 sensitivity and
  89.1 specificity).
• FHR decelerations following vibroacoustic
  stimulation.

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Ultrasonography of the Umbilical Cord

• Traditionally not performed uniformly due to
• Objective difficulty (2D depiction of free
  floating narrow structure in 3D environment).
• Fetal movement
• Lack of immediate availability of color Doppler
  imaging
• Lack of institutional guidelines.
• Dependent on determination of sonographer.

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Ultrasonography of the umbilical cord

• The umbilical cord exhibits coiling (helical
  twists),
• Fetuses with non-coiled umbilical cords are at
  increased risk for adverse perinatal outcome.
• Nuchal cords, have less vascular coiling.
• Potentially, the coiled umbilical cord may be
  able to withstand vascular stretching and
  compression associated with nuchal entanglement.

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Ultrasonography of nuchal cords

• Requires a high-degree of suspicion (due to the
  sonolucent nature of umbilical vessels).
• Represents a fixed point of the umbilical cord,
  specifically in the vicinity of the fetal neck.
• Become significantly easier with high-resolution
  ultrasound with the divot sign representing
  circular indentations of the fetal nuchal skin
  (Ranzini et al, Obstet Gynecol 199993854).
• Care should be excercised not to confuse
  posterior cystic masses, folds of skin or
  amniotic fluid pockets, with the divot sign.

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Ultrasonography of Nuchal Cords

• The condition renders itself to color Doppler
  imaging.
• Both sagittal and axial sections (cross-section
  and linear, respectively) are required to avoid
  overdiagnosis.
• Doppler flow velocimetry may be applied to
  confirm diagnosis.
• 3D ultrasound may improve prenatal diagnosis.

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Color Doppler Ultrasound of Nuchal Cord

• Color Doppler imaging correctly identifies 72 of
  single, and 94 of multiple nuchal cords found at
  birth.
• Overall sensitivity of color Doppler ultrasound
  in the prenatal detection of nuchal cords is 79.
• Greater sensitivity noted after, rather than
  before 36 weeks gestation (93 vs. 67),
  possibly reflecting spontaneous reduction with
  earlier diagnosis.
• (Jauniaux et al, Ultrasound Obstet Gynecol
  19922417-9)

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Color Doppler Ultrasound of Nuchal Cord

• Reported sensitivity and specificity of
  intrapartum color Doppler ultrasound diagnosis of
  nuchal cord, 96 and 97, respectively.
• (Funk et al, Geburtshilfe Frauenheilkd
  199555623-7)
• (Qin et al, Ultrasound Obstet Gynecol
  200015413-7)
• 3D surface imaging does not provide more useful
  information than conventional 2D or color Doppler
  ultrasound in detecting nuchal cords.
• (Hanaoka et al, Ultrasound Obstet Gynecol
  200219471-4)

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Single Nuchal Cord(sagittal view)
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Single Nuchal Cord(color Doppler, sagittal view)
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Single Nuchal Cord (color Doppler, axial view)
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Single Nuchal Cord(color Doppler, axial view)
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Single Nuchal Cord (color Doppler, axial view)
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Double Nuchal Cord (sagittal view)
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Double Nuchal Cord(color Doppler, sagittal view)
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Double Nuchal Cord(color Doppler, axial view)
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Double Nuchal Cord (color Doppler, axial view)
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Doppler Flow Velocimetry of Nuchal Cord

• Abnormal Doppler flow waveforms suggesting an
  obstruction to flow have been reported in
  association with true knots of the cord.
• Potential waveform abnormalities include
• systolic notching of the umbilical artery
  waveform.
• poststenotic acceleration of umbilical vein flow.
• absent end diastolic flow (reported with nuchal
  cord).

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Doppler Velocimetry of Nuchal Cord
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Doppler Velocimetry ofNuchal Cord
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Doppler Velocimetry ofNuchal Cord
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3D UltrasoundSingle Nuchal Cord
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3D Ultrasound Double Nuchal Cord
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3D UltrasoundTriple Nuchal Cord
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Ultrasonography of Nuchal Cords

• Disregard?
• dont ask, dont tell
• Inform?
• Monitor?
• Intervene?

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Suggested Modified Management

• Information regarding the presence of nuchal
  cord(s) should not be withheld.
• Findings should be discussed openly in real-time
  with the patient, preferably by a Perinatologist.
• Should be explicitly stated on the written report
  generated following US examination.

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Patient Counseling, Should Address

• Reassurance as to the high-probability of
  unaffected outcome.
• Critical importance of fetal movement assessment.

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In addressing Clinical Management

• Number of involved nuchal loops.
• Amniotic fluid volume status (AFI).
• Gestational age.
• Fetal growth.

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Fetal Testing Indicated

• Significantly decreased amniotic fluid volume.
• Postdates.
• Fetal growth restriction.
• Decreased fetal movements.

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Fetal Testing Should Include

• Nonstress test.
• Biophysical profile.
• Doppler flow velocimetry
• Potentially, evoked tests including
• Vibroacoustic stimulation
• Oxytocin challenge test

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With less than optimal fetal testing

• Delivery should be considered

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Potentially, application of these new guidelines,
may decrease the occurrence of third-trimester
in-utero fetal demise associated with nuchal
cords.
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In summaryUltrasonographic depiction of a
nuchal cord should be

• Recorded in the patients chart.
• Fowarded to the patient and her physician.
• Managed with close fetal surveillance including
  fetal movement counts and interval fetal testing.
• In selected cases, may indicate delivery.