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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5786_Библиотеки_им_академика_М_И_Перельмана.pdf
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Therefore, Doppler ultrasound evaluation in multiple pregnancies may be of
use for selected conditions.
Investigation of the uteroplacental circulation by uterine Doppler velocimetry in midgestation demonstrated lower mean artery resistance in twins compared to singletons. This may reflect the larger placental implantation area.
Compared to screening efficacy in singletons, prediction of pre-eclampsia and
FGR in twins was lower (sensitivity of about 30% and 20%, respectively).
However, since the prevalence of complications is increased in multiple pregnancies, although sensitivity is lower, the positive predictive value of an abnormal test is higher.
50
Several Doppler studies have examined flow velocity waveforms of various
vessels in twins. In uncomplicated twin pregnancies, there are no differences in
the umbilical artery and middle cerebral artery resistances compared to singleton pregnancies. In the presence of growth restriction and/or weight discordance,
Doppler of the umbilical artery has been reported to be a valuable adjunct.14
A recent prospective randomized controlled multicentre trial investigated the
performance of umbilical artery Doppler added to standard ultrasound biometry
Ultrasound in obstetrics and gynaecology
in the management of twin pregnancies.20 In this study, close surveillance resulted
in a lower than expected fetal mortality in both the non-Doppler and Doppler
groups. There were no differences between the two groups with respect to antenatal and postnatal outcomes. However, a major concern in this study is that it
does not address the issue of chorionicity.
Currently, Doppler plays a critical role in the management of monochorionic
pregnancies complicated by TTTS and is incorporated into a widely used staging
system.
42,43
The association of increased nuchal translucency with abnormal flow
pattern in the ductus venosus in first-trimester monochorionic twins may be an
early manifestation of a haemodynamic imbalance between a donor and a recipient, thus predicting manifestation of TTTS.33 Colour Doppler sonography may also
help in the identification and differentiation of the communicating placental vessels
prior to endoscopic laser surgery. Doppler detection of artery-to-artery anastomosis
carries a decreased risk of TTTS and improves stage-independent survival.48 Fetal
Doppler findings in manifest TTTS do reflect circulatory changes due to hypovolaemia in the donor and congestive heart failure following cardiac overload in the
recipient (see Fig. 11.6B). Successful laser ablation of intertwin anastomosis may
lead to resolution of the disease and the concomitant Doppler changes. Return of
donor umbilical artery end-diastolic blood flow and reappearance of positive flow
during atrial contraction in the recipient ductus venosus can be found after therapy
as well as transient increase in venous pulsatility in the donor fetus.
Twin reversed arterial perfusion (TRAP) sequence is a rare complication in
monochorionic twins. It is characterized by artery-to-artery anastomosis with
the feature of reversed umbilical perfusion from the donor fetus to the acardiac
twin and may result in cardiac failure of the donor. Serial echocardiographic and
venous Doppler ultrasound examinations are most helpful in monitoring these
pregnancies and discriminating between those suitable for conservative manage-
224
ment and others that will benefit from cord occlusion.
18,50
20
21
49
References
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7. Baschat AA. Doppler application in the
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V, Peacock JL. Doppler ultrasound of the
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Rangsiprakarn R. Prediction of discordant
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15. Favre R, Cherif Y, Kohler M et al. The
role of fetal nuchal translucency and
ductus venosus Doppler at 11–14 weeks
of gestation in the detection of major
congenital heart defects. Ultrasound Obstet
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16. Ferrazzi E, Bozzo M, Rigano S et al.
Temporal sequence of abnormal Doppler
changes in the peripheral and central
circulatory systems of the severely growthrestricted fetus. Ultrasound Obstet Gynecol
2002;19:140–146
17. Frusca T, Soregaroli M, Valcamonico A,
Guandalini F, Danti L. Doppler velocimetry
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women. Early Hum Dev 1997;48:177–185
18. Geipel A, Berg C, Germer U et al. Doppler
assessment of the uterine circulation in
the second trimester in twin pregnancies:
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restriction and birth weight discordance.
Ultrasound Obstet Gynecol 2002;20:541–545
19. Gembruch U, Meise C, Germer U, Berg
C, Geipel A. Venous Doppler ultrasound
in 146 fetuses with congenital heart
disease. Ultrasound Obstet Gynecol
2003;22:345–350.
20. Giles W, Bisits A, O'Callaghan S, Gill A,
for the DAMP Study Group. The Doppler
Assessment in Multiple Pregnancy
randomised controlled trial of ultrasound
biometry versus umbilical artery Doppler
ultrasound and biometry in twin pregnancy.
Br J Obstet Gynaecol 2003;110:593–597
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21. Gratacós E, Van Schoubroeck D, Carreras E
et al. Impact of laser coagulation in severe
twin–twin transfusion syndrome on fetal
Doppler indices and venous blood flow
volume. Ultrasound Obstet Gynecol
2002;20:125–130
22. Harman CR, Baschat AA. Comprehensive
assessment of fetal wellbeing: which
Doppler tests should be performed? Curr
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23. Harrington K, Cooper D, Lees C, Hecher K,
Campbell S. Doppler ultrasound of the
uterine arteries: the importance of bilateral
notching in the prediction of pre-eclampsia,
placental abruption or delivery of a smallfor-gestational-age baby. Ultrasound Obstet
Gynecol 1996;7:182–188
24. Hecher K, Campbell S, Snijders R,
Nicolaides K. Reference ranges for fetal
venous and atrioventricular blood flow
parameters. Ultrasound Obstet Gynecol
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1994;4:381–390
25. Hecher K, Bilardo CM, Stigter RH,
Ville Y, Hackelöer BJ, Kok HJ. Monitoring of
fetuses with intrauterine growth restriction:
a longitudinal study. Ultrasound Obstet
Gynecol 2001;18:564–570
26. Hershkovitz R, Kingdom JC, Geary M,
Rodeck CH. Fetal cerebral blood
flow redistribution in late gestation:
identification of compromise in small
fetuses with normal umbilical artery
Doppler. Ultrasound Obstet Gynecol
2000;15:209–212
27. Hollis B, Prefumo F, Bhide A, Rao S,
Thilaganathan B. First-trimester uterine artery
blood flow and birth weight. Ultrasound
Obstet Gynecol 2003;22:373–376
28. Irion O, Masse J, Forest JC, Moutquin JM.
Prediction of pre-eclampsia, low birthweight
for gestation and prematurity by uterine
artery blood flow velocity waveforms
analysis in low risk nulliparous women. Br J
Obstet Gynaecol 1998;106:88–89
29. Karsdorp VH, van Vugt JM, van Geijn HP
et al. Clinical significance of absent
or reversed end diastolic velocity
waveforms in umbilical arterey. Lancet
1994;344:1664–1668
30. Li H, Gudnason H, Olofsson P, Dubiel M,
Gudmundsson S. Increased uterine artery
vascular impedance is related to adverse
outcome of pregnancy but is present in
only one-third of late third-trimester preeclamptic women. Ultrasound Obstet
Gynecol 2005;25:459–463
31. Mari G, Deter RL, Carpenter RL
et al. Noninvasive diagnosis by Doppler
ultrasonography of fetal anemia due
to maternal red-cell alloimmunization.
Collaborative Group for Doppler
Assessment of the Blood Velocity
in Anemic Fetuses. N Engl J Med
2000;342:9–14
32. Mari G. Middle cerebral artery peak
systolic velocity for the diagnosis of fetal
anemia: the untold story. Ultrasound Obstet
Gynecol 2005;25:323–330
33. Matias A, Montenegro N, Areias JC.
Anticipating twin–twin transfusion
syndrome in monochorionic twin
pregnancy. Is there a role for nuchal
translucency and ductus venosus blood
flow evaluation at 11–14 weeks? Twin Res
2000;3:65–70
34. Mavrides E, Sairam S, Hollis B,
Thilaganathan B. Screening for aneuploidy
in the first trimester by assessment of blood
flow in the ductus venosus. Br J Obstet
Gynaecol 2002;109:1015–1019
35. Neilson JP, Alfirevic Z. Doppler ultrasound
for fetal assessment in high risk pregnancies.
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36. Oepkes D, Seaward G, Vandenbussche F
et al for the Diamond Study Group.
Doppler ultrasonography versus
amniocentesis to predict fetal anemia.
N Engl J Med 2006;355:156–164
37. Ozcan T, Sbracia M, d'Ancona RL, Copel JA,
Mari G. Arterial and venous Doppler
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adverse perinatal outcome Ultrasound
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38. Papageorghiou AT, Yu CK, Bindra R,
Pandis G, Nicolaides KH for the
Fetal Medicine Foundation Second
Trimester Screening Group. Multicenter
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growth restriction by transvaginal
uterine artery Doppler at 23 weeks of
gestation. Ultrasound Obstet Gynecol
2001;18:441–449
39. Papageorghiou AT, Yu CK, Cicero S,
Bower S, Nicolaides KH. Secondtrimester uterine artery Doppler
screening in unselected populations: a
review. J Matern Fetal Neonatal Med
2002;12:78–88
40. Papageorghiou AT, Yu CK, Erasmus IE,
Cuckle HS, Nicolaides KH. Assessment of
risk for the development of pre-eclampsia
by maternal characteristics and uterine
artery Doppler. Br J Obstet Gynaecol
2005;112:703–709
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41. Papageorghiou AT, Roberts N. Uterine artery
Doppler screening for adverse pregnancy
outcome. Obstet Gynecol 2005;17:584–590
42. Quintero RA, Morales WJ, Allen MH,
Bornick PW, Johnson PK, Kruger M. Staging
of twin–twin transfusion syndrome.
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43. Quintero RA, Dickinson JE, Morales WJ
et al. Stage-based treatment of twin–twin
transfusion syndrome. Am J Obstet Gynecol
2003;188:1333–1340
44. Severi FM, Bocchi C, Visentin A et al.
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the outcome of third-trimester smallfor-gestational-age fetuses with normal
umbilical artery Doppler. Ultrasound
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45. Smrcek JM, Krapp M, Axt-Fliedner R et al.
Atypical ductus venosus blood flow pattern
in fetuses with severe tricuspid valve
regurgitation. Ultrasound Obstet Gynecol
2005;26:180–182
46. Spencer K, Yu CKH, Cowans NJ, Otigbah C,
Nicolaides KH. Prediction of pregnancy
complications by first-trimester maternal
serum PAPP-A and free ß-hCG and with
second-trimester uterine artery Doppler.
Prenat Diagn 2005;25:949–953
47. Takahashi Y, Kawabata I, Tamaya T.
Characterization of growth-restricted
fetuses with breakdown of the brain-sparing
effect diagnosed by spectral Doppler.
J Matern Fetal Med 2001;10:122–126
48. Tan TY, Taylor MJ, Wee LY, Vanderheyden
T, Wimalasundera R, Fisk NM. Doppler
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stage-independent survival in twin–
twin transfusion. Obstet Gynecol
2004;103:1174–1180
49. Weisz B, Peltz R, Chayen B et al. Tailored
management of twin reversed arterial
perfusion (TRAP) sequence. Ultrasound
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50. Yu CK, Papageorghiou AT, Boli A,
Cacho AM, Nicolaides KH. Screening for
pre-eclampsia and fetal growth restriction
in twin pregnancies at 23 weeks of gestation
by transvaginal uterine artery Doppler.
Ultrasound Obstet Gynecol 2002;20:
532–534
51. Zimmerman R, Carpenter RJ Jr, Durig P,
Mari G. Longitudinal measurement of
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complicated by red cell alloimmunisation:
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2002;109:746–752
Evaluation of fetal and uteroplacental blood flow
227
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Invasive procedures in obstetrics
Yves Ville
ABSTRACT
The main focus in fetal invasive testing is fetal karyotyping, although increasingly
molecular studies on fetal material are being carried out. Invasive techniques include
chorion villus sampling and fetal blood sampling as the sources of fetal tissue. The
technique and safety of these procedures are presented. Intrauterine fetal blood
transfusion is indicated in severe fetal anaemia such as in red cell alloimmunization,
fetomaternal haemorrhage and parvovirus B19 infection with fetal hydrops. Fetal
shunting is limited to very selective fetal diseases following careful evaluation,
i.e. obstructive uropathy, macrocystic congenital malformation of the lungs (CCAM)
or pleural effusions associated with fetal hydrops. Ultrasound plays a pivotal role in
selective fetocide performed in higher-order multiple pregnancies.
KEYWORDS
Amniocentesis, chorion villus sampling, fetal blood sampling, fetal shunting,
selective fetocide.
INTRODUCTION
The introduction of a needle through the maternal abdomen under ultrasound
guidance is the basis for invasive prenatal diagnosis and fetal therapy to treat a
critically ill fetus. All intrauterine invasive procedures in obstetrics should be carried out under continuous real-time ultrasound control. These procedures carry a
risk of fetal loss and/or preterm delivery or intrauterine death.
The most common reason for fetal invasive testing is karyotyping and there are
three main techniques used to obtain fetal tissue: chorion villus sampling (CVS),
amniocentesis (AC) and fetal blood sampling (FBS). All three have been credited
with various risks and it is important to critically appraise the indications for each
229
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5wks 11wks 16wks 40wks
1%
2%
15%
Fig. 12.1 Spontaneous fetal loss rate throughout gestation. (Reproduced with permission
from Hook EB. Down syndrome live births and spontaneous abortions of unknown
karyotype. Prog Clin Biol Res 1985;163C:21–24.)
of these procedures. It is vital to understand that the risk of spontaneous miscarriage is present throughout the pregnancy, even though it decreases with increased
gestation: from 15% at 5 weeks down to 1% at 16 weeks of gestation (Fig. 12.1).
Ultrasound in obstetrics and gynaecology
Non-specific risks involve fetal loss which may be idiopathic or may occur as a
result of direct fetal injury with subsequent exsanguination or infection. Preterm
delivery, intra-amniotic haemorrhage and chorioamnionitis also contribute to the
morbidity of invasive procedures. Adequate methodology should include registration of the outcome of all pregnancies without excluding any complication from
a causal relationship with the procedure performed.
COUNSELLING
Genetic counselling will not be discussed in detail in this chapter. However, a few
guidelines will be mentioned, since counselling is an essential factor in all invasive
procedures. Counselling involves helping the individual and her family to understand the indication, the expected results, the failure rate and the procedurerelated risks as well as available alternatives. Counselling should take place before
the procedure is carried out. It should be done in a place where privacy, confidentiality and autonomy are guaranteed. It should not be done on an examination
couch but outside the procedure room. Counselling requires time, patience and
skills to convey the information in understandable language considering the individual's education and ethical beliefs.
The counselling should be documented in writing and should included the
time(s) and the nature of the counselling as well as what was discussed. The
documentation may be needed for future reference, possibly in connection with
medico-legal claims. Written consent prior to an invasive procedure does not substitute for documented information about counselling.
TRAINING
Training in invasive procedures is not easy and should always be supervised by a
230
competent senior operator. Although programmes for training of junior doctors
✩✩✩✩✩✩✩✩✩✩✩ ✩
Long axis
Long axis
of the uterus
of the uterus
Table plane
Table plane
45°
45°
3cm
3cm
Right angle
to the table
3 cm, 45°
in obstetric ultrasound are now well established, the opportunity to acquire the
specific skills necessary to perform FBS is currently available in only a few major
fetal medicine centres where training is carried out with active supervision of the
trainee. The technique described below allows for control of every step of the procedure and anticipation of the next one through full visualization of the needle
path and that of the target. Supervision can therefore be timely and explicit without increasing the anxiety already felt by the patient as a result of the uncertainty
over the outcome of the pregnancy.
The use of phantoms helps the inexperienced operator to master basic technique and also reduces uncertainty. It is recommended that the first 100 procedures be performed with such a set-up. There are several types of phantoms
described in the literature.
1,2
Some are even home-made.2 They all use anechoic
gel in which the target is placed.
The particular aim of the training is to be able to direct a needle transabdominally towards a target in the fetoplacental unit under complete operator control
and continuous visualization of both the target and the needle. In our experience,
invasive procedures may be performed with a free-hand technique by a single
operator. We use a curvilinear transducer, visualizing clearly the abdominal wall
and placing the target in the centre of the screen. The needle should be visualized
from its entry through the skin and the zoom should not be used until the needle
is approaching the target. The transducer is ideally held in the left hand of a righthanded operator. The needle may be inserted 3 cm away from the transducer at an
angle of 45° with the horizontal probe (Fig. 12.2).
Invasive procedures in obstetrics
Fig. 12.2 Operative plan of any invasive procedure showing the position of the transducer,
the target on the screen and the angle at which the needle should be introduced.
231
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Some of the most difficult aspects of the procedure are:
visualizing the cord longitudinally at either the placental or umbilical
•
insertion
maintaining the transducer in the proper position throughout the
•
procedure
introducing the needle through the skin at the correct angle and distance
•
from the transducer
advancing the needle under full vision towards and into the cord
•
introducing the needle into the umbilical vein through the Wharton's jelly
•
surrounding the cord
finding the target again and repositioning the needle in the same
•
alignment if the target has moved.
THE PROCEDURES
Each of the invasive procedures is presented below, starting with chorion villous
Ultrasound in obstetrics and gynaecology
sampling (CVS) which, in the chronology of the pregnancy, is the first invasive
test which can performed safely and reliably. The basic technique and equipment
for each procedure are described, along with known complications, safety aspects
and any special considerations regarding multiple gestations.
232
ASEPSIS
Common to all the procedures is asepsis. The site is cleaned with an antiseptic
solution (usually chlorhexidine 0.5% in spirit or iodine solution) and the mother's
lower abdomen is draped with sterile towels. The ultrasound probe may be placed
in a sterile plastic bag. Iodine ensures good contact between the wrapped probe
and the skin; sterile Vaseline may also be used. The operator wears sterile gloves.
CHORIONIC VILLOUS SAMPLING
The aim of chorionic villous sampling (CVS) is to insert a sampling device, either
a needle or a biopsy forceps, inside and parallel to the great axis of the chorion
frondosum in order to sample an adequate amount of trophoblast (Fig. 12.3).
Several techniques have been developed over the last 10 years for CVS either
transabdominally or transcervically using catheters, needles or biopsy forceps.
CVS should be done after 10 completed weeks of gestation. This timing is
•
derived from the analysis of cases of severe transverse limb abnormalities
or oromandibular-limb hypogenesis syndrome reported after CVS
performed prior to 66 days of gestation.20 CVS may be performed up to
14–15 weeks but some may prefer it as a first-line technique up to term.
The question remains whether CVS sampling after 10 weeks has the
potential to cause more subtle defects but most centres performing CVS
after 10 weeks have not seen an increase in limb defects.
4
3
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L
L
L
L
l
l
1. Anterior Insertion
1. Anterior Insertion
2. Fundal Insertion
2. Fundal Insertion
1. Posterior Insertion
1. Posterior Insertion
Fig. 12.3 The CVS needle must be inserted in the longitudinal axis of the trophoblast to
allow sufficient course for the needle to be moved back and fore.
Invasive procedures in obstetrics
A transabdominal approach is preferable since the infection-related risk of
•
fetal loss seems to be higher when the transcervical technique is used. Three
techniques for transabdominal sampling are mainly used. In the single-needle
approach, a 12–15 cm 20 gauge spinal needle is used.5 Aspiration is usually
achieved by connecting a catheter to the hub of the needle and to a 20 mL
syringe together with hand grip while the operator is moving the needle to
and fro within the trophoblast 10–15 times, following a straight 4–5 cm course
under continuous ultrasound guidance. The double-needle technique uses an
outer guide needle introduced down through the skin and myometrium at the
edge of the chorion frondosum. This can be either an 18 gauge thin-walled
needle or a standard 16–17 gauge spinal needle. A smaller, usually 20 gauge,
sampling needle is then passed through and used for the direct sampling as
described above. The advantage of the double-needle technique is that it
allows for quantitative and qualitative assessment of the sample while the first
needle is still in the uterus and the procedure can be completed if necessary
without the need for a repuncture. Some prefer that local anaesthesia be given
down to the myometrium along the needle path.
A variation of the latter is the use of a biopsy forceps passed down a
•
16–18 gauge needle.
Chorionic villus sampling in multiple gestations
The best and, in fact only, screening test for fetal aneuploidy in the first trimester
in twin pregnancies is nuchal translucency thickness (NT) measurement, although
a recent study suggests that false-positive rates and invasive diagnostic procedures
233
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are reduced when first-trimester biochemistry is added.21 In dichorionic twins
NT is measured above the 95th centile in 5% of the twins; in monochorionic
pregnancies these figures are reported to be up to 9% and 13% respectively. If
selective termination is an option in an aneuploid dichorionic twin, it should be
noted that the outcome is dependent upon the timing of reduction with a sharp
increase in the fetal loss rate after 16 weeks.22 CVS performed at 11–14 weeks
has therefore become a real alternative to amniocentesis in twins. Precise determination of chorionicity is an absolute prerequisite and is easy to ascertain at
11–14 weeks of gestation. This will help to determine the necessity of sampling
only one or both trophoblasts. Indeed, in monochorionic gestations, heterokaryotic
twins are an anecdotal phenomenon and sampling of the trophoblast close to the
high-risk twin should lead to identical karyotype in both fetuses.
When the sampling of both twins is indicated, as in non-chromosomic genetic or
biochemical testing, two needle insertions are necessary in order to provide the best
approach to the trophoblast of each dichorionic twin. One should consider the risk
of two needle insertions at this stage as compared to a single needle insertion to perform an amniocentesis at 15 weeks. This should be carefully evaluated, taking into
Ultrasound in obstetrics and gynaecology
account the risk of finding an affected pregnancy as compared to that of fetal loss.
Safety
There are several large studies reporting on the safety of CVS,6 including more
than 200,000 procedures, suggesting that CVS is associated with a low pregnancy
loss, comparable to second-trimester amniocentesis.
7
234
AMNIOCENTESIS
Cytogenetic analysis and diagnosis of intra-amniotic infection are the main diagnostic indications. Drainage of polyhydramnios and medical treatment of fetal
disorders are rare therapeutic indications.
Amniocentesis can be performed from 15–16 completed weeks of gestation
onwards. This restriction appears reasonable, since several randomized studies
have clearly demonstrated that amniocentesis carries a higher fetal loss and morbidity rate when performed before 14 completed weeks as compared to later
amniocentesis, and to CVS performed at the same gestational age. This is likely to
be due to the presence of the extracoelomic space. Even when it has become virtual, the amniotic membrane can remain incompletely fused to the uterine wall
until up to 14–15 weeks. Dry taps may then occur since the amniotic membrane
will be tented by the needle and not perforated. The so-called ‘early amniocentesis’ should therefore be abandoned for safety reasons.
A site of puncture is chosen to avoid placental tissue and umbilical cord in the
needle path. Isoimmunization is likely to be increased by a transplancental approach,
but there is little evidence to suggest this would be more deleterious in terms of
intra-amniotic bleeding or fetal loss.
9,10
Indeed, a transplacental approach in the late
first trimester could well decrease the risk of membrane tenting when the extraamniotic space has virtually disappeared but the amnion is not yet attached.
8,9