Cervical Ultrasound

Cervical
Ultrasound

  

• Griff
  Jones, Darryl Maxwell (Division of Perinatology,
  Ottawa General Hospital and Fetal Medicine Unit
  Guy’s and St.Thomas’ Hospital, London)
  
  
  Cervical Ultrasound in Pregnancy 
  
  
  Prog. Obstet & Gynaec, 14, p.80
  
    
  
  
  The uterine cervix undergoes considerable
  physiological, biochemical and anatomical changes
  during the transition between the antenatal and
  intrapartum periods. Digital examination
  consistently underestimated length by more than
  13mm. In contrast, ultrasonographic measurements
  correlated well with those obtained using a ruler on
  the postoperative specimen.
  
    
  
  
  Transabdominal ultrasound
  
  The average cervical length to be between 35-40mm.
  Up to 6mm dilatation at the internal os was normal
  with no significant cervical change seen from the
  10th to the 36th week of gestation.
  
   
  
  
  115 women with risk factors for cervical
  incompetence were studied. Patient management was
  largely based on clinical (as opposed to ultrasound)
  findings. Of the women with evidence of moderate
  cervical weakness on ultrasound, one-third were
  found to have clinically normal cervices. With
  expectant management, 75% delivered before 34 weeks’
  gestation. Most of the remaining two-thirds,
  underwent cerclage with 25% delivering before 34
  weeks.
  
   
  
  
  Riley et al report a 50% risk of preterm birth in
  women co-incidentally found to have cervical
  shortening and membrane funneling on transabdominal
  scanning.
  
   
  
  
  
  Transvaginal ultrasound:
  
  Brown et al suggest that adequate cervical images
  were more likely to be obtained by transvaginal
  scanning than by transabdominal U.S.G. The cervix
  could be visualized transvaginally 99% of the time.
  When transabdominal and transvaginal cervical length
  measurements from the same woman were compared,
  transabdominal measurements were on average 5mm
  longer, presumably secondary to bladder filling. Of
  the 30 women, 29 demonstrated an increase in
  cervical length with increasing bladder volume.
  Confino et al also reported cases in which
  quantified bladder filling or manual pressure
  exerted via the transducer led to significant
  reductions in internal os dilatation in patients
  with suspected incompetence.
  
   
  
  
  Digital examination only assesses that portion of
  the cervix below the vaginal wall. Goldberg et al
  found the mean cervical lengths in 43 pregnant women
  measured by transvaginal ultrasound (39mm) to be
  over twice as long as those measured digitally
  (19mm) by experienced examiners. Similarly, Sonek et
  al found that digital measurement of cervical length
  showed a poor correlation with vaginal
  ultrasonography.
  
    
  
  
  
  Safety and acceptability:
  
   
  
  
  Heath et al questioned 100 consecutive women about
  the acceptability of a transvaginal scan at 23 weeks
  gestation: 94% experienced no, or minimal,
  discomfort only and 98% reported no or only mild
  embarrassment. Half of the women found it to be less
  uncomfortable than a speculum examination.
  
   
  
  
  Normal values for cervical length
  
  There appears to be no clinically significnat
  difference between the mean cervical lengths of
  primiparous and multiparous women.
  
   
  
  
  It is possible that ethnic differences in cervical
  length exist. The work of National Institute of
  Child Health and Human Development Maternal-Fetal
  Medicine Unit Network has shown a short cervix (£
  25mm) to be significantly more common in high risk
  women.
  
    
  
  
  
  DIAGNOSTIC ROLE
  
  
  Preterm Labour
  
   
  
  
  Murakawa et al studied 32 women presenting with
  threatened preterm labour. None of the 15 women with
  cervical lengths greater than 30 mm delivered
  preterm. If the cervix was less than 30mm, 65%
  delivered preterm and all early births were
  identified. All women with a cervical length below
  20mm delivered preterm.
  
   
  
  
  Gomez et al developed the term cervical index to
  include information about endocervical length and
  funnel length in a single figure. Funneling was
  present in 58% of women and associated with a nearly
  3-fold increase in the risk of preterm birth. A
  complex statistical analysis suggested that a
  cervical index ³0.52, cervical length < 18mm,
  funnel length > 9mm and funnel width > 6mm
  were all significantly associated with preterm
  birth. All the patients who delivered preterm had a
  funnel present.
  
   
  
  
  
  Cervical anatomy
  
  
  The ability to diagnose (or exclude) placenta
  praevia is one of the main benefits ascribed to
  antenatal ultrasound. Provided that the placental
  edge is at least 20mm from the internal os, a
  vaginal birth appears safe.
  
   
  
  
  
  Cervical incompetence
  
  
  Cervical conization may iatrogenically predispose to
  cervical incompetence.
  
   
  
  
  Management Role
  
  Assessment of risk of preterm birth
  
  Cervical length
  
   
  
  
  3000 women of mixed-risk were screened at both 24
  and 28 weeks of gestation. The mean cervical length
  was approximately 35mm and the overall incidence of
  spontaneous preterm birth £ 35 weeks’ gestation was
  4.3%. There was a clear inverse relationship between
  cervical length and risk of preterm birth. A short
  cervix (£ 25mm) was associated with an 8%
  probability of spontaneous preterm delivery £ 35
  weeks gestation in low-risk parous women. In
  high-risk women, this probability climbed to 31%
  with the same cervical measurement.
  
   
  
  
  The second study was carried out at a single inner
  city centre in the UK. Results from cervical scans
  at 23 weeks’ gestation were blinded unless the
  length was less than 16mm. A cervical length of £
  15mm at 23 weeks’ gestation carried a risk of
  spontaneous delivery £ 32 weeks of 50% and
  correctly identified 58% of these births.
  
    
  
  
  The third study was from a well-defined geographical
  area in Helsinki, Findland with a 99% white
  population. The mean cervical length was just over
  40mm and a short cervix was defined as one £ 29mm,
  corresponding to the 3rd centile.
  
   
  
  
  All three studies confirm the ability of
  transvaginal cervical ultrasound to reliably
  stratify women by risk of spontaneous preterm birth.
  Even more importantly, the background or pre-test
  risk of spontaneous preterm birth must be taken into
  account when interpreting cervical sonograms.
  
   
  
  
  
  Membrane funneling
  
  
  If the funnel length was greater than the length of
  closed cervix below it, 75% of patients delivered
  before 37 weeks’ gestation. A funnel width exceeding
  15mm was another risk factor. Heath et al found that
  all women with a cervical length £ 15mm exhibited
  funneling compared to only one-third of those with a
  cervical length of 16-25mm.
  
   
  
  
  
  Dynamic changes.
  
  
  Sonek subsequently reported the same phenomenon in
  women not believed to have cervical incompetence,
  using transvaginal scanning. He stated that the
  funneling could be accentuated or brought on by
  gentle manual pressure on the uterine fundus and
  advocated this as an ‘internal os stress test’.
  
   
  
  
  At present, transfundal pressure cannot be
  standardised. More recently, reports have appeared
  advocating the use of a postural challenge, with the
  cervix being scanned first while the mother is
  supine and then when upright.
  
   
  
  
  
  Cervical cerclage:
  
  
  The final report of the MRC/RCOG Multicentre
  Randomised Trial of Cervical Cerclage suggested
  benefit in only 4% of cases with prior clinical
  uncertainty. Detailed inspection revealed that
  cerclage improved outcome only after three or more
  previous very early deliveries. The mean interval
  between cerclage removal and delivery was 2.3 weeks.
  
   
  
  
  
  Cerclage placement
  
  
  Both Andersen et al and Quinn reported all the
  McDonald sutures in their series to be in the middle
  third of the cervix. The optimal placement of a
  suture was obtained in the single patient that was
  treated with a Shirodkar-type cerclage, involving
  preliminary dissection of the anterior vaginal wall.
  
   
  
  
  Post cerclage follow up
  
  Between 25-30% of patients developed funneling above
  the cerclage.
  
   
  
  
  
  Twin pregnancies
  
  
  Goldenberg et al scanned 147 twin pregnancies at 24
  and 28 weeks’ gestation. A cervical length of less
  than 25mm was twice as common in twin pregnancies as
  in singletons and became more common as gestation
  advanced, occurring in 18% of women at 24 weeks and
  33% at 28 weeks.
  
   
  
  
  
  Cervical ultrasound and routine antenatal care
  
  
  Although Zalar suggested that knowledge of
  transvaginal cervical ultrasound measurements can
  lead to a reduction in spontaneous low birth-weight
  deliveries, it cannot yet be concluded that cervical
  ultrasound has a place in routine antenatal care in
  low-risk pregnancies.
  
   
  
  
  Preterm prelabour rupture of the membranes
  
  The authors were unable to demonstrate a significant
  relationship between cervical length and the number
  of days to spontaneous labour.
  
   
  
  
  
  TECHNIQUES FOR CERVICAL SCANNING
  
  
  Transabdominal
  
  Cervical images are best obtained transabdominally
  with a full bladder. Unfortunately, this is
  associated with artificial lengthening of the cervix
  and potential closure of a dilated internal os.
  Therefore, it will lead to false reassurance in some
  cases. The external os can also be difficult to
  identify transabdominally. In the studies of Varma
  et al, an inflated Foley catheter balloon was placed
  against it to overcome this problem.
  
    
  
  
  
  Transvaginal
  
  
  This remains the gold standard for cervical imaging.
  Sonek et al have advocated the use of a probe with a
  240° scanning field, this would appear to be
  unnecessary. Pressure on the cervix can falsely
  increase the measured length and obscure funneling
  at the internal os. Failing to appreciate that not
  all cervical canals follow a straight line can lead
  to underestimates of length. At least 3 measurements
  should be taken and the shortest (not the average)
  used. Most authors advise scanning over
  approximately 5 min to detect dynamic changes. The
  presence of a funnel should be noted and funnel
  width and length recorded. Some authors have
  reserved the term ‘funnel’ for membrane protrusions
  greater than 5mm down the endocervical canal,
  referring to anything less as ‘nippling’.
  
   
  
  
  
  Transperineal scanning
  
  
  A glove-covered 3.5MHz or 5 MHz sector or
  curvilinear transducer is applied to the perineum to
  visualize the cervix. It is reportedly easily
  tolerated by patients, but is best performed before
  digital or speculum examination which, by
  introducing air into the vagina, produce artefact.
  The technique has been particularly useful in cases
  of prolapsing membranes when cerclage is not being
  undertaken. The contrast provided by the funnel or
  membranes usually allows excellent visualization and
  serial monitoring. Transperineal ultrasonography may
  prove to be an acceptable mass screening technique.
  
   
  
  
  
  CONCLUSIONS:
  
  
   
  
  
  As proposed by Iams et al, ultrasound imaging
  suggests cervical competence to be a continuous
  variable. Infection has attracted considerable
  interest as one of the most important aetiologies
  behind preterm labour and delivery. A weak or short
  cervix could offer less resistance to ascending
  infection. Half have positive amniotic fluid
  cultures. 
  
   
  
  
  Iams et al have recently reported that a cervical
  length of less than 25mm at 24 weeks’ gestation is
  strongly associated with subsequent perinatal
  infection. Bacteria can ascend the genital tract
  attached to motile sperm. Antibiotics may play just
  as important a role as cervical cerclage in
  preventing prematurity. As prostaglandins are
  implicated in the process of cervical ripening,
  non-steroidal anti-inflammatories such as
  indomethacin may have role for ultrasonographic
  cervical change, at least before 28 weeks’
  gestation. Cervical ultrasound undoubtedly allows a
  far better assessment of risk than clinical
  examination.
  
   
  
  

• 
  Frank Johnstone (Department of Obstetrics and
  Gynaecology, University of Edinburgh UK)
  
  
  Drug Use in Pregnancy
  
  
  Progress in Obstetric and Gynaecology vol.14
  
   
  
  
  This article is about a broad range of drugs which
  have some psycho-active properties and which are
  used for non-therapeutic reasons in pregnancy.
  
   
  
  
  All the drugs (with the possible exception of
  benzodiazepines) appear to have a common final
  pathway. They all act by increasing dopamine
  release. But for all of them, the common end-point
  where dopamine is released forms part of a circuit
  known as the brain reward system, consisting of a
  small group of nerve cells extending from the
  ventral tegmental area of the midbrain to limbic
  areas such as the nucleus accumbens, with
  projections to the pre-frontal cortex. The markedly
  reduced activity in the brain reward circuits on
  withdrawal also explains dependence.
  
   
  
  
  Over the past few decades, use has spread to most
  countries of the world. This is due partly to a
  general increase in use of psycho-active drugs,
  improvements in communication and transportation and
  the globalisation of the world economy. Indeed,
  tobacco companies have used international trade
  agreements to open up markets in the developing
  world, and the same factors facilitating trade in
  legal goods also facilitate trade in illicit drugs.
  
   
  
  
  Many women, who do not acknowledge any problem with
  their drug pattern, may present for the first time
  to the health care system because of the pregnancy.
  This presents a window of opportunity for harm
  minimisation and education. Pregnancy can be a great
  motivator. Drug use in pregnancy is already known to
  be a major public health problem.
  
   
  
  
  
  Some Effects of Drugs on Pregnancy
  
  
  Effects in animal studies (often with high doses)
  may be due to maternal toxicity rather than direct
  effects on the fetus (e.g. drug induced anorexia).
  There may be selection bias based on obvious chaotic
  drug use, so that the women studies are quite
  unrepresentative of population use. The small
  numbers studied may be inadequate to study
  infrequent events. Because of editorial and reviewer
  bias there may be preferential publication of
  studies which report harmful effects. Many drug
  users are polydrug users and this makes it difficult
  to isolate the effect of one drug. There are major
  problems in separating the effects of drug use from
  the other adverse personal, psychological and social
  circumstances in which drug use is taking place.
  
   
  
  
  
  Opioids
  
  
  Injecting street heroin is dangerous and in most
  cohorts of users the mortality is at least 1% each
  year. The commonest cause of death is respiratory
  depression due to overdose. The other major medical
  complications relate largely to non-sterile
  injecting, resulting in transmission of hepatitis B,
  and most importantly hepatitis C and HIV.
  
   
  
  
  There is no convincing evidence that opioids cause
  fetal abnormalities.They probably have a small
  inhibiting effect on fetal growth, though this is
  less than the effects of smoking. In all large
  studies, there is a modest increase in perinatal
  mortality due to preterm delivery and late pregnancy
  stillbirth, but it is uncertain how much of this
  drug is a drug effect rather than due to the effect
  of other variables. Preterm labour does seem to be
  more common in women injecting drugs rather than
  taking orally, possibly related to a higher risk of
  alternation between intoxication and withdrawal with
  relatively short acting injected drugs. An increase
  in meconium staining of the liquor is also
  consistently reported, related to episodes of fetal
  drug withdrawal.
  
   
  
  
  There is a high rate of neonatal abstinence syndrome
  (NAS), ranging from 50-90% in women taking opiates
  daily. Symptoms may last for weeks or even months in
  a mild form. Typically, babies feed poorly and have
  tremor on handling, a shrill cry, sneeze and may
  have watery stools. Untreated, they can develop
  projectile vomiting and electrolyte disturbance,
  seizures and coma. 
  
   
  
  
  The largest study of 1760 cases of sudden infant
  death syndrome, showed a 7 times increased risk with
  maternal methadone use and a 5 times increased risk
  with heroin use. 
  
   
  
  
  Drug effects, and the consequences of an unstable,
  impoverished environment, are very difficult to
  disentangle, but this remains an area of concern.
  
   
  
  
  
  Cocaine.
  
  
  As well as its central action, this drug has
  important peripheral effects on inhibition of
  re-uptake of noradrenaline in presynaptic nerve
  terminals. Catecholamines diffuse from the nerve
  terminals and the resulting high vascular levels
  cause vasoconstriction, tachycardia, hypertension
  and perhaps uterine contractility.
  
   
  
  
  The vasoconstrictive properties of cocaine raise the
  possibility that there might be fetal damage during
  episodes of fetal ischaemia or subsequent
  reperfusion. However, the overall population risk
  for users does not seem very high, perhaps because
  only those with high dosage at key gestations are
  vulnerable. A large number of studies in women are
  consistent in reporting a decrease in birth weight.
  Preterm delivery is common and, although it is very
  difficult to adjust for multiple co-variates this is
  probably also a direct drug effect.
  
   
  
  
  
  Nicotine
  
  
  Of the 4000 compounds in tobacco smoke, there is
  good evidence that nicotine is the key drug of
  addiction and nicotine, carbon monoxide and cyanide
  are thought to have the greatest adverse effect on
  the fetus. World-wide, this is the most harmful drug
  for pregnancy.
  
   
  
  
  There are well documented increased risks of
  spontaneous abortion, ectopic pregnancy, placenta
  praevia, placental abruption, preterm premature
  rupture of the membranes and preterm delivery. Birth
  weight is depressed by about 250g, with an increased
  risk of significant intra-uterine growth
  restriction. Intrauterine death in late pregnancy is
  more common. Overall, at least in the US, smoking
  causes an estimated 20-30% of the low birth weight
  rate and 10% of fetal and infant mortality.
  Postnatally, maternal milk production is reduced by
  about 30%. There are strong relationships with
  sudden infant death syndrome; respiratory disease
  and hospital admission in the first year of life;
  and an ongoing effect on respiratory disease in
  childhood. There are small effects on physical,
  mental and behavioural development of the child, of
  uncertain clinical significance.
  
   
  
  
  There may be other long-term complications.
  Potentially carcinogenic tobacco metabolites are
  present in the first urine of babies whose mothers
  smoked in pregnancy. The babies of women who smoke
  were found to have a much higher frequency of a
  genomic deletion event that is commonly found in
  leukaemia and lymphomas of early childhood.
  
   
  
  
  
  Benzodiazepines
  
  
  Diazepam overdose in 25 pregnancies was not
  accompanied by obvious fetal problems. Withdrawal
  may occur in the neonate, typically with
  irritability and slowness to feed and respond. There
  may be ‘floppy infant syndrome’ with poor suck,
  feeble cry, hypotonia, and sometimes poor
  temperature control.
  
   
  
  
  
  Cannabis
  
  
  Most studies have not reported an association
  between prenatal marijuana exposure and
  morphological abnormalities of the baby.
  
   
  
  
  
  Amphetamines
  
  
  Data currently available do not allow any accurate
  estimate of risk.
  
   
  
  
  
  Designer drugs
  
  
  The most widely used drugs at present are
  amphetamine analogues. Ecstasy (3,4
  methylenedioxymethyl amphetamine, MDMA) is one
  derivative related chemically to both amphetamines
  and hallucinogens.
  
   
  
  
  
  Alcohol
  
  
  This is the only one of these drugs which is proven
  to be teratogenic. Fetal alcohol syndrome (FAS) has
  been reviewed in a previous issue of this series. A
  wide range of other alcohol-related birth defects
  appear to occur with heavy drinking. These adverse
  effects have been well documented with very high
  maternal intakes. Judging by animal experiments,
  alcohol may affect fetal brain development at any
  gestation. Threshold effects on subsequent reading,
  spelling and arithmetic abilities in children have
  been reported at low intakes.
  
   
  
  
  Volatile substances
  
  The commonest substance is cigarette lighter refills
  (butane) but a wide range of products are used.
  
    
  
  
  
  OPTIONS FOR DRUG MANAGEMENT
  
  
  Many women who are not truly dependent on their drug
  will stop spontaneously as soon as they know they
  are pregnant. This applies to 15-20% of women who
  smoke, to many women who use ecstasy or cannabis
  episodically and it is also true of some controlled
  users of opiates.
  
   
  
  
  It is said that most girls who smoke 3 cigarettes as
  adolescents will become dependent, with an average
  duration of dependence of 40 years. Sadly, having
  been recruited in adolescence, half of all smokers
  die because of the habit, one-third of them before
  the age of 65 years. 20% of all deaths in developed
  countries are caused by smoking: an enormous human
  cost which can be completely avoided.
  
   
  
  
  Therefore, antenatal care should include advice to
  stop smoking, with easy access to programmes to
  support those who choose this. Brief intervention by
  family doctors is effective. Cutting down is
  probably not a useful aim. 
  
   
  
  
  Trying to persuade the woman to stop drugs may
  simply alienate her, lead to return to a more
  chaotic drug use pattern, and result in
  non-attendance for antenatal care. Therefore, the
  different options of detoxification, substitution
  and maintenance and other aspects of damage
  limitation need to be considered with full
  understanding of the woman’s aspirations and
  particular social and psychological circumstances.
  
   
  
  
  For most women who are dependent and who have a
  long-standing opiate habit, substitution and
  maintenance is usually the preferred option. The
  drug of choice is methadone linctus. Methadone
  maintenance treatment has been extensively
  researched, and has been shown to be effective.
  Substitution should be prescribed as part of a
  package including social and psychological support.
  
   
  
  
  Acute detoxification in pregnancy is not often
  appropriate but should be an option. The risks of
  withdrawal have probably been exaggerated in the
  past, and can be minimised by appropriate drug
  therapy to the mother. Detoxification can be carried
  out in the mid-trimester quite safely and this has a
  place in overall management.
  
   
  
  
  Slow reduction may be preferred by some women for
  opiates, and is necessary for benzodiazepines.
  
   
  
  
  Much of the management of drug misuse is damage
  limitation rather than cure, and in patients who
  continue to inject, it is essential to ensure that
  they have access to clean equipment, by needle
  exchange.
  
     
  
  
  Maternity Care in Drug Users
  
  Another important obligation on community care staff
  is effective liaison and communication with other
  agencies. Nothing is so guaranteed to reduce
  confidence as different agencies giving out
  different messages.
  
      
  
  
  The opiate using woman should be warned that
  neonatal abstinence syndrome may occur, that her
  dose is not a reliable predictor, that it can
  present after several days and can last for weeks.
  She needs also to know that NAS is usually easily
  manageable.
  
     
  
  
  Repeated non-sterile injection over years destroys
  peripheral veins, often leaving track marks (thrombosed,
  fibrosed veins). Occasionally there may be concern
  about the ability of the woman to look after her
  child. Many women worry that their baby may be taken
  away into care purely because they use drugs.
  
     
  
  
  Occasionally, there maybe incidents involving
  violence or the threat of violence, most often
  caused by the partner or visiting friends in
  hospital.
  
     
  
  
  Adequate pain relief can be obtained with opiates
  although much more frequent injections are likely to
  be needed. Because of the high fear about pain which
  many drug users have, epidural anaesthesia may be
  very useful.
  
      
  
  
  Naloxone must not be used to reverse opioid induced
  respiratory depression in the newborn because of the
  risk of precipitating an acute opiate withdrawal
  crisis.
  
      
  
  
  After delivery, a chart scoring for neonatal
  abstinence syndrome is helpful for all concerned.
  This is, of course, only one aspect of assessment.
  Withdrawing babies can usually be treated without
  drug management, with lots of cuddling, small
  frequent feeds, and patience. Babies may need
  neonatal unit care to maintain hydration and may
  need sedation. The logical drug is simply
  replacement of opiate, and neonatal morphine
  solution can be used.
  
        
  

• Alessandro Ghidini, Nicola Strobelt, Anna Locatelli, Eloisa Mariani, Maria Giovanna Piccoli, and Patrizia Vergani
  
  Isolated Fetal Choroid Plexus Cysts : Role of Ultrasonography in Establishment of the Risk of Trisomy 18
  
  Am J. Obstet Gynecol April 2000, Volume 182, Number 4, Pgs. 972-977
  
      
  
  
  Objective – The significance of isolated choroid plexus cysts found by ultrasonographic scan during the second trimester as a marker for trisomy 18 is 
  
  still debated. We analyzed our data and reviewed the series published in the English-language literature to calculate the likelihood ratio of trisomy 18 in the presence of isolated choroid plexus cysts; that is, the factor by which the individual risk of trisomy 18 is increased in the presence of isolated choroid plexus cysts.
  
      
  
  
  Study Design – Likelihood ratios were calculated as ratio of the sensitivity to the faise-positive rate. Sensitivity was defined as the rate of isolated choroid plexus cysts detected at midgestation among fetuses with trisomy 18. False-positive rate was defined as the rate of choroid plexus cysts detected at midgestation in the population without trisomy 18. The sensitivities of all published series reporting rates of choroid plexus with trisomy 18 and in low-risk populations were included in the analysis. To these we added all cases of trisomy 18 diagnosed at our institution during the period January 1, 1988, through June 30, 1998, in which prenatal ultrasonographic examination was performed between 14 and 24 weeks’ gestation. 
  
     
  
  
  Results – The prevalence of second-trimester ultrasonographic detection of isolated choroid plexus cysts among fetuses with trisomy 18 was 6.7% [ 13/194]. Whereas that in the population without trisomy 18 was 0.9% [752/79, 583]. The likelihood ratio associated with isolated choroid plexus cysts was therefore 7.09 [95% confidence interval, 3.97 -12.18]
  
     
  
  
  Conclusion – The presence of isolated second-trimester choroid plexus cysts increases the base risk of trisomy 18 by a factor of 7.09. This likelihood ratio can be multiplied by the risk calculated according to maternal age to obtain the individual risk of trisomy 18 and thus permit more accurate counseling of the patient.
  
  
      

• Karim D. Kalache, Roland Wauer, Harald Mau, Rabih Chaoui, and Rainer Bollmann
  
  Prognostic Significance of the Pouch Sign in Fetuses with Prenatally Diagnosed Esophageal Atresia
  
  Am J. Obstet Gynecol April 2000, Volume 182, Number 4, Pgs. 978-981
  
     
  
  
  Objective – Esophageal atresia may be diagnosed prenatally by ultrasonographic visualization of the blind-ending esophagus during fetal swallowing, which is referred to as the pouch sign. Our purpose was to determine whether this sign can be used to predict outcomes of affected fetuses. 
  
     
  
  
  Study Design – Four cases of esophageal atresia diagnosed in our center during the past 2 years were analyzed, in conjunction with 3 cases from published series. Ultrasonographic features of the pouch sign were categorized according to localization.
  
     
  
  
  Results – In the neck pouch group [ n=3] 1 fetus died in utero and 1 died before a corrective operation could be undertaken. In the only fetus of this group to survive a staged repair was necessary because of a long atretic gap. Conversely, 3 of the 4 fetuses with a mediastinal pouch survived after a successful corrective operation, and primary repair was possible in all cases.
  
     
  
  
  Conclusions – The base of the proximal blind-ending esophagus can be clearly localized by means of ultrasonography. Our data suggest that a neck pouch may be associated with an adverse outcome. This information may be useful in counseling parents when esphageal atresia is diagnosed prenatally.