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SOFT FETAL
ULTRASOUND FINDINGS
Compiled by the Genetics Team at The Credit Valley Hospital
Last updated February 2008

Soft Fetal Ultrasound Findings
Page 2
This document refers to the ultrasound finding of a soft sign, as compared to a clear cut
structural anomaly. There is very little information about outcomes when more than
one soft finding is seen on a fetal ultrasound. The information herein refers to isolated
soft findings, meaning the ultrasound is otherwise unremarkable.
If the ultrasound is done at a gestation earlier than 18 weeks, a detailed fetal ultrasound
around 18-19 weeks can be considered, since visualization of the fetus is better at later
gestations, allowing for exclusion of other soft signs, and a better assessment of the
original finding. However, in many of the soft ultrasound findings, the natural history is
that the sign can disappear, but one cannot fully ignore the original finding.
The impact of Maternal Serum Screening (MSS) or Integrated Prenatal Screening (IPS)
in estimating the risk of a true fetal chromosome anomaly in the presence of a soft
ultrasound finding is unknown. Only for a choroid plexus cyst has the literature begun
to evaluate the contribution of MSS or IPS.
It is important to remember that the risk of a significant fetal chromosome anomaly
increases with maternal age. A woman is eligible for prenatal chromosome testing
when she is 35 or greater at the time of delivery (32 or older if twins).
Although likelihood risks have been estimated for some of the soft signs, it is important
to note that in many of the references below, the women were from high risk categories,
potentially inflating the risk estimates. Also, often the number of cases reported is
small.
General References:
Shipp and Benacerraf (2002). Second trimester screening for chromosome
abnormalities. Prenatal Diagnosis 22:296-307.
Smith-Bindman R. et al (2001). Second-trimester ultrasound to detect fetuses with
Down syndrome. JAMA 285:1044-1055.
Van den Hof MC. et al. (2005). Fetal soft markers in obstetric ultrasound. JOGC
27:592-612.
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CONTENTS
FIRST TRIMESTER SOFT SIGNS
1. Absent nasal bone
2. Increased nuchal translucency
SECOND TRIMESTER SOFT SIGNS
1. Choroid plexus cyst
2. Drooping choroids
3. Mild ventriculomegaly
4. Enlarged cistern magna
5. Nasal bone hypoplasia
6. Increased nuchal fold
7. Echogenic cardiac focus
8. Single umbilical artery
9. Pyelectasis
10.Echogenic bowel
11.Short femur
12.Short humerus
Soft Fetal Ultrasound Findings
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Soft Fetal Ultrasound Findings
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1. ABSENT NASAL BONE February 2008
A small nose and midface hypoplasia are well-recognized clinical features of Down
syndrome. Nasal bone ossification has been absent in a significant number of aborted
fetuses with DS of varying gestations. This information provided credence to the idea of
prenatal first trimester study of the nasal bone as an additional marker for DS.
Required components for nasal bone imaging have been suggested (2) . This includes a
mid-sagittal view of the fetus with the fetus occupying most of the image with clear fetal
margins.
Several studies have now been published suggesting the absence of the nasal bone in
the first trimester is associated with DS. The majority of studies emerge from Cicero et
al (Nicolaides group in the UK) (1) . Six important pieces of information have emerged:
• Nasal bone more likely to be absent at earlier gestations. In euploid fetuses with
CRL between 45 and 54 mm, the nasal bone was absent in 4.7% cases. At CRL
between 75 and 84 mm, the nasal bone was absent in only 1% of cases. Nasal
bone assessment should be limited to first trimester fetuses with CRL> 45 mm.
• Data in the studies are from a high-risk pregnancy group. Low risk population yet
to be studied. Prefumo et al (3) suggest nasal bone hypoplasia performs poorly as
a marker for DS in an unselected population. This raises the question of its use
as a secondary marker rather than a primary marker.
• Examining a high-risk group opting for CVS, the nasal bone was absent in 43/59
(73%) trisomy 21 fetuses and only 3/603 (0.5%) euploid fetuses. If this
ultrasound sign is combined with NT and biochemistry markers it is predicted the
detection of DS would increase to 93% with the same false positive rate of 5%.
• The same investigators found that absence of the nasal bone is also associated
with trisomy 18, trisomy 13, and monosomy X.
• There appears to be an association between absent nasal bone, fetal crownrump
length, and nuchal translucency. In aneuploid pregnancies, nasal bone
absence occurs more frequently with increasing NT. When NT was at the 95 th
percentile or less the likelihood of absent nasal bone was greatest. The
likelihood decreased as the NT increased.
• There is a relationship between ethnicity and nasal bone development.
Further evaluation of nasal bone assessment performance in a low risk population must
be determined and sufficient adequately trained centres with appropriate educational
and credentialing procedures must be available before this can be used as part of
provincial screening in Ontario. However, use of this ultrasound marker as an
independent determinant of fetal chromosome testing cannot be ignored in first
trimester fetuses with CRL>45 mm.
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References:
Soft Fetal Ultrasound Findings
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1. Cicero S et al. (2006) Nasal bone in first-trimester screening for trisomy 21. Am J
Obstet Gynecol 195:109-114
2. Rosen T et al. (2007) First-trimester ultrasound assessment of the nasal bone to
screen for aneuploidy. Obstet and Gynecol. 110:2(1)399-404
3. Prefumo F et al. (2006) First-trimester nuchal translucency, nasal bones, and
trisomy 21 in selected and unselected populations. Am J Obstet Gynecol
194:828-833
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Soft Fetal Ultrasound Findings
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2. INCREASED FETAL NUCHAL TRANSLUCENCY 11-14 weeks February 2008
Nuchal translucency (NT) is the sonographic appearance of a subcutaneous collection
of fluid behind the fetal neck. The 95th percentile measurement is 3.0 mm (which
advances slightly with gestational age), and 99 th percentile measurement is constant at
3.5 mm. NOTE: reliability of the measurement is operator dependent. Typically, this
measurement is done as part of Integrated Prenatal Screening (IPS) or First Trimester
Screening (FTS). Screening using only the NT is to be discouraged. However, if the
measurement is significantly increased, it warrants offering counselling.
Associations:
An increased NT per se does not constitute a fetal abnormality.
The larger the NT measurement, the greater is the risk of an adverse outcome.
• Chromosome anomalies (50% trisomy 21, 25 % trisomy 13/18, 10% Turner
syndrome, 10% other)
• congenital heart disease (>99 th centile -> overall likelihood ratio of 22.5 X population
risk, with 1% of screened population > 99 th centile, somewhat correlates with the
size of the NT
• single gene conditions, (with or without mental handicap)
• other anatomic anomalies –Likelihood ratio correlates with size of NT for
lethal/severe anomalies,
• fetal demise – Likelihood ratio = 5 X but does not correlate with the size of the NT
With normal chromosomes, a normal 19 week ultrasound and echocardiogram, and with
regression of the NT, there is up to a 95% chance of normal pregnancy outcome,
without major malformations.
Counselling and Management:
• Chromosome testing is offered, by CVS if gestation allows, or by amniocentesis. If
IPS has been started, the patient can finish the screen, but if the NT is >4 mm, the
result will be screen positive. A screen negative result does not rule out fetal trisomy
18 or 21. Chromosome testing includes the offer of microarray analysis if G-banded
analysis is normal.
• When gestation allows, the patient can consider an ultrasound at 15 weeks, to
assess viability and progression/regression of the finding, before having invasive
fetal chromosome testing by amniocentesis.
• Ultrasound at 19– 20 weeks gestation to look for fetal structural anomalies
• Echocardiogram of the heart and great vessels at 19-20 weeks if NT>3.5 mm. If
below 99 th centile, careful ultrasound, with examination of the great vessels and
heart is appropriate.
• Newborn physical examination by a clinician aware of the prenatal ultrasound
finding.
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References:
Soft Fetal Ultrasound Findings
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Atzel A et al., (2005). Relationship between nuchal translucency thickness and
prevalence of major cardiac defects in fetuses with normal karyotype. Ultrasound
Obstet Gynecol. 26:154-157.
Bilardo CM. et al., (2007). Increased nuchal translucency thickness and normal
karyotype: time for parental reassurance. Ultrasound in Obstet Gynecol 30:11-18.
Haddow JE et al. (1998). Antenatal screening for Down's syndrome: where are we and
where next? Lancet 352:336-337.
Hyett J et al. (1999). Using fetal nuchal translucency to screen for major congenital
cardiac defects at 10-14 weeks of gestation: population based cohort study. BMJ
318:81-85. (See also the accompanying editorial on page 70-71)
Muller MA et al. (2004). Disappearance of enlarged nuchal translucency before 14
weeks gestation: relationship with chromosomal abnormalities and pregnancy outcome.
Ultrasound in Obstetrics and Gynecology 24(2):169-174
Nicolaides et al (2002). Increased fetal nuchal translucency at 11-14 weeks. Prenatal
Diagnosis 22:308-315
Snijders RJM et al., (1998). UK multicentre project on assessement of risk of trisomy 21
by maternal age and fetal nuchal translucency thickness at 10-14 weeks of gestation.
Souka AP et al., (2005). Increased nuchal translucency with normal karyotype. Am J
Obstet Gynecol 192:1005-1021.
Westin M et al., (2007) by how much does increased nuchal translucency increase the
risk of adverse pregnancyoutcome in chromosomally normal fetuses? A study of 16260
fetuses derived from an unselected pregnant population. Ultrasound Obstet Gynecol
29:150-158.
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SECOND TRIMESTER SOFT SIGNS
Soft Fetal Ultrasound Findings
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1. Choroid Plexus Cyst (CPC) February 2008
As the choroid plexus develops, the covering epithelium changes and choroidal villi are
formed. The spaces between these projections (villi) may be enlarged by fluid or debris
to create choroid plexus cysts.
Natural History:
• 1-4% of all pregnancies:
• almost all disappear by 28 weeks gestation
• no long term clinical consequences for cerebral development
• size, location and number do not appear to influence outcome
Association:
• increased risk of trisomy 18, which becomes significant only for those > 35 at
delivery
• weakly associated with trisomy 21 (Down syndrome)
Counselling:
a) Maternal age , prenatal screen not done – amniocentesis is available based
on age, amniocentesis should be considered, - if patient is not keen on
amniocentesis and if gestation permits, MSS could be undertaken, for if it is screen
negative, likely the risk of trisomy 18 is diminished.
e) If there are any additional soft signs, referral for counselling and the offer of fetal
chromosome is appropriate.
References:
Bird LM, et al. (2002) Choroid plexus cysts in the mid-tirmester fetus. Prenatal
Diagnosis 22:792-7.
Cheng PJ, et al. (2006) Association of fetal choroid plexus cysts with Trisomy 18 in a
population previously screened by nuchal translucency thickness measurement. JSoc
Gynecol Investig 13:280-4
Gratton et al, (1996) Choroid plexus cysts and trisomy 18: risk modification based on
maternal age and multiple marker screening. Am J Obstet Gynecol 175:1493-7.
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Soft Fetal Ultrasound Findings
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Ouzounian JG, et al. (2007). Isolated choroid plexus cyst or echogenic cardiac focus on
prenatal ultrasound: is genetic amniocentesis indicated? Am J Obstet Gynecol.
196:595.e1-e3.
2. DROOPING CHOROID (dangling choroid) February 2008
The medial wall of the lateral ventricle appears to be separated from the choroid. The
normal measurement should be less than 3 mm. The normal size of the lateral
ventriclular atrial measurement is less than 10 mm.
Natural History:
Unknown – often resolves by the subsequent ultrasound.
Associations:
There are no clear associations with a recognized adverse clinical outcome. However,
there is a small concern this might be the prelude to cerebral ventriculomegaly (which
has a clear association with increased adverse outcomes).
Counselling:
• Monitor ventricular size and look for other anomalies with ultrasound at 18, 22-23
weeks and 32-36 weeks. If ventriculomegaly (lateral ventricle atrial measurement of
10 mm or more) is subsequently found, further counselling is warranted.
• Amniocentesis - Since there is an association of mild cerebral ventriculomegaly with
an increased risk of a chromosome anomaly, amniocentesis can be offered.
Reference:
Hertzberg, BS et al., (1994) Choroid Plexus-ventricular wall separation in fetuses with
normal-sized cerebral ventricles at sonography: postnatal outcome, Am J Radiol
163:405-10.
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Soft Fetal Ultrasound Findings
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3. MILD CEREBRAL VENTRICULOMEGALY February 2008
Mild ventriculomegaly is defined as an axial diameter of greater than 9.9 mm, measured
across the atrium of the posterior or anterior horn of the lateral ventricles at any
gestation. Sometimes, it is described as a separation of more than 3 mm of the choroid
plexus from the medial wall of the lateral ventricle. Ventriculomegaly is distinguished
from hydrocephalus where there is an atrial diameter of greater than 15 mm.
Hydrocephalus is not considered here.
Natural History:
• The prevalence is about 1 in 700 low risk pregnancies.
• Complete information of the natural history of isolated ventriculomegaly is not yet
available, since careful long term studies have not been conducted. The size can
stay the same or become smaller.
• The majority of children appear to have normal development.
• There is perhaps a 9% chance of cognitive disabilities, which can very in severity.
This can occur even with resolution. There is a suggestion in the literature that
those with a smaller increase in the ventricular measurement might have a smaller
chance of an abnormal outocome. However, given the lack of appropriate longterm
studies, it is suggested the risk of an abnormal outcome be treated with
circumspection.
• Progression to hydrocephalus can occur, but the chance of this is not well known.
Progression is thought to occur in a minority of cases. There is an increased chance
of other cerebral structural anomalies which might not be detectable on an antenatal
ultrasound.
Associations:
• The chance of a fetal chromosome anomaly is estimated to be 3.8% (0-28.6%). The
commonest is trisomy 21. It can be found in single gene disorders or sporadic
conditions.
• Ventriculomegaly is weakly associated with fetal infections, most commonly
cytomegalovirus (CMV) or toxoplasmosis.
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Counselling:
Soft Fetal Ultrasound Findings
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• detailed ultrasound to assess for other structural anomalies or soft signs, if not
already completed
• Additional ultrasound around 22 weeks, to look for possible progression to
hydrocephalus. If persistent, another in the third trimester is suggested.
Uncommonly, an MRI can detect additional anomalies, but this is not offered
routinely.
• fetal chromosome testing
• intial and convalescent maternal titres for CMV, toxoplasmosis, parvovirus
• postnatal assessment for dysmorphic features and neuroimaging, if persistent
• postnatal followup of developmental milestones
References:
Kelly EN, et al., (2001). Mild ventriculomegaly in the fetus, natural history, associated
findings and outcome of isolated mild ventriculomegaly. A literature review. Prenat
Diagn 21:697.
Wax JR, et al., (2004). Mild Fetal Cerebral Ventriculomegaly: diagnosis, clinical
associations, and outcomes. Obstetrical and Gynecological Survey, 58:407.
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Soft Fetal Ultrasound Findings
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4. ENLARGED CISTERNA MAGNA December 2007
The cisterna magna is a fluid collection posterior to the cerebellum. It is seen as an
echo-free triangle with the point oriented towards the cerebellar vermis. Prenatally, the
anterior/posterior diameter should be < 10 mm, with a normal appearing vermis, and
without hydrocephalus. Visualization can be challenging, and must be done in the
correct plane.
Natural History:
• Mega cisterna magna occurs in approximately 1/8200 pregnancies.
• When isolated, most times the finding is benign. However, there are no large
prospective series, with adequate outcome data.
• Since visualization of the posterior fossa can be limited and because the
development of the posterior fossa structures is a late embryologic event, there
remains an unknown chance there could be other CNS anomalies, possibly
detectable later in gestation, such as a Dandy-Walker malformation/variant.
Associations:
There might be an increased risk of a fetal chromosome anomaly, but more typically this
is when the enlarged cisterna magna is found in association with other anomalies.
Counselling:
• When isolated, this is not an indication for fetal chromosome testing, but further
investigation to look for other anomalies is indicated since some studies suggest that
it is not isolated in more than 50% of cases.
• Another ultrasound at 21-23 weeks is suggested. If there is any uncertainty about
the fetal brain findings, an MRI would be considered.
• The patient can consider prenatal chromosome testing.
References:
Van den Hof MC., et al. (2005) Fetal Soft markers in obstetric ultrasound. JOGC
27:592-612.
Haimovici JA., et al. (1997) Clinical signficiance of isolated enlargemetn of the cisternal
magna (>10 mm) on prenatal sonography. J Ultraosund Med 16:731-734.
Long A., et al. (2006) Outcome of fetal cerebral posterior fossa anomalies. Prenat Diag
26:707-710.
Foranzo F et al. (2007) Posterior fossa malformation in fetues: a report of 56 further
cases and a review of the literature. Prenat Diagn 27:495-501.
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Soft Fetal Ultrasound Findings
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5. NASAL BONE HYPOPLASIA February 2008
The optimal definition for this established second trimester marker for DS seems to be
multiples of the median of nasal bone for the gestational age (1, 2, 3) .
The regression curves used were based on NB of white fetuses. For race or ethnicity
other than
white a multiplicative correction factor was used to obtain MoM (African-American,
Hispanic, Asian, other).
Measurement of NB is performed as described by Sonek et al (4) . This takes into
account the angle of measurement and placement of calipers for the length of the nasal
bone.
Maternal age at delivery is independent of nasal bone MoM in both affected and
unaffected fetuses.
There is a clear association between absent nasal bone and aneuploidy. Fetal
chromosome testing should be offered in these cases. The association between Down
syndrome (and possibly trisomy 18) and nasal bone hypoplasia is less clear.
Amniocentesis could be offered.
References:
1. Cusick W et al. (2007) Likelihood ratios for fetal trisomy 21 based on nasal bone
length in the second trimester: how best to define hypoplasia? Ultrasound Obstet
Gynecol 30:271-274.
2. Odibo A et al. (2007) Defining nasal bone hypoplasia in second-trimester Down
syndrome screening: does the use of multiples of the median improve screening
efficacy? Am J Obstet and Gynecol 361 e1-e4.
3. Gianferrari et al. (2007) Absent or shortened nasal bone length and detection o
Down syndrome in second trimester fetuses. Obstet and Gynecol 109(1):371-375
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Soft Fetal Ultrasound Findings
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6. INCREASED NUCHAL FOLD February 2008
Measurement of the thickness of the skin of the posterior neck of >6mm in second
trimester, between 16 weeks, 0 days, and

Soft Fetal Ultrasound Findings
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7. ECHOGENIC INTRACARDIAC FOCUS September 2007
The ultrasound visualizes an area (usually of the left ventricle) which is at least as
echodense as bone, about 2 mm in diameter (can be up to 6 mm.) The pathologic basis
is a discrete linear mineralization of the myocardial fusiform bundle of the chordae
tendinae but why it occurs is unknown.
Natural History:
• Found in 0.46 - 3% of pregnancies
• Might occur more frequently in fetuses of women of Asian, African and Middle
Eastern ethnicities.
• No long term cardiac consequences known.
• Most disappear by the third trimester, but even when it persists, normal cardiac
function is expected.
Associations:
• Associated with an increased risk of a chromosome problem, typically Down
syndrome.
• If occuring in the right ventricle, possibly the risk of a chromosome anomaly
might be higher than if located in the left.
Counselling:
• Controversy exists as to whether amniocentesis should be offered due to
significantly different conclusions by various authors.
• Patient can consider amniocentesis.
• Further ultrasound/echocardiograms are not required.
References:
Achiron et al, (1997) Obstet Gynecol 89:945-8.
Huggon C et al (2001) Ultrasound Obstet Gynecol 17:11-16.
Wax JR et al (2000) Ultrasound Obstet Gynecol 16(2):123-127.
Sotiriadis A et al (2003) Diagnostic performance of intracardiac echogenic foci for Down
syndrome: a meta-analysis. Obstet Gynecol 101:1009-1016.
Smith-Bindman R et al (2001). Second-trimester ultrasound to detect fetuses with
Down syndrome. A meta-analysis. JAMA 285:1044-1055.
Goncalves, et al. (2006). Int J Gynecol Obstet 95:132-137.
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Soft Fetal Ultrasound Findings
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8. SINGLE UMBILICAL ARTERY September 2007
Natural History:
• 0.3% -1% of 19 weeks gestation (total births and late pregnancy losses)
• most have a normal outcome
Associations
• 19% had other ultrasound detectable anomalies (i.e. not isolated), often renal,
cardiac or brain anomalies
• If isolated, most newborns are normal, but there remains up to a 7% risk of other
structural anomalies, not seen on antenatal ultrasound (heart, brain, kidney,
limbs described)
• small size (average weight 365 gm lower)
• Possible increase in risk of preterm delivery
• Slight increase in the risk of a chromosome abnormality, but usually with other
structural anomalies
Counselling and Management:
• Detailed u/s at 19 weeks, including heart and great vessels
• Chance of a fetal chromosome anomaly with an isolated single umbilical artery,
is low enough that fetal chromosome testing is not warranted
• Follow fetal growth with ultrasound
• Careful physical examination for additional anomalies after birth
References:
Cantanzarite et al, (1995). Prenatal diagnosis of the two vessel cord: implications for
patient counselling and obstetric management. Ultrasound Obstet Gynecol 5:98-105.
Parill et al, (1995). The clinical significance of a single umbilical artery as an isolated
finding on prenatal ultrasound. Obstet Gynecol 85:570-2.
Chow JS, Benson CB, Doubilet PM (1998). Frequency and nature of structural
anomalies in fetuses with single umbilical arteries. J Ultrasound Med 17:765-768.
Rinehart BK, Terrone DA, Taylor CW, Issler CM, Larmon JE, Roberts WE (2000).
Single umbilical artery is associated with an increased incidence of structural and
chromosomal anomalies and growth restriction. Am J Perinat 17:229-232.
Gornall AS, Kurinczuk JJ, Konje JC (2003). Antenatal detection of a single umbilical
artery: does it matter? Prenat Diagn 23:117-123.
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Soft Fetal Ultrasound Findings
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9. RENAL PYELECTASIS (pelviectasis) September 2007
The AP diameter of renal pelvis is equal to or > 5 mm at gestations up to 32 weeks, 6
days OR equal to or > 7 mm at gestations of 33 weeks to term. Any measurement >10
mm is hydronephrosis.
Natural History :
• occurs in about 0.7%- 3% of all pregnancies, more common in males
• 80% most resolve with no long term consequences, either in utero or in the first year
Associations:
• congenital hydronephrosis (diagnosed as > 10 mm after birth) – risk correlates with
larger measurements
• vesico-ureteric reflux (VUR)
• more prevalent in fetus with trisomy 21 (isolated mild pyelectasis is present In about
2% of babies with Down syndrome). The estimated likelihood ratio is low at 1.9, with
very wide confidence intervals.
Counselling and Management:
• Ultrasounds – Since pelviectasis can progress, monitoring by ultrasound at 22-23
weeks and after 28 weeks is suggested
• Ultrasound does not discriminate between obstructive and non-obstructive
uropathy in the second trimester
• If persistent and greater than 10 mm after 28 weeks gestation, pediatric
consultation is strongly suggested after delivery.
• VUR can still occur after birth, even with regression of pelviectasis
• Patient can consider amniocentesis.
References:
Courteville, JE et al, (1992). Fetal Pyelctasis and Down syndrome: Is genetic
amniocentesis warranted? Obstet Gynecol 79:770-772.
Wickstrom EA et al. (1996). Obstet Gynecol 88:379-382.
Chudleigh T. (2001). Mild Pyelectasis. Prenat Diagn 21:936-941.
Chudleigh PM et al. (2001). The association of aneuploidy and mild fetal pyelectasis in
an unselected population: The results of a mulitcentre study. Ultrasound Obstet
Gynecol. 17:197-202.
Tovianinen-Salo S., et al. (2004). Fetal hydronephrosis: is there hope for consensus?
Pediatr Radiol 34:519-529.
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Soft Fetal Ultrasound Findings
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10. ECHOGENIC BOWEL February 2008
The appearance on ultrasound of fetal bowel with an echogenicity similar to or greater
than surrounding bone.
Natural History:
• Found in about 0.6-2.4% of all second trimester fetuses
• Sometimes persists, sometimes disappears
Associations:
• usually is a normal variant
• swallowed bloody amniotic fluid from a placental abruption or an invasive
procedure, intraluminal inspissated meconium, or mesenteric ischemia.
Increased risks of the following have been observed, but quantitation of the risk
varies in the literature:
• chromosome anomalies (trisomy 21 and others)
• cystic fibrosis
• congenital infection (CMV, occasionally other prenatal infections)
• intrauterine growth retardation, which is associated with an increased risk of
perinatal morbidity and mortality
• GI malformations
• alpha Thalassemia in Oriental population
Counselling:
• The patient can consider amniocentesis.
• Cystic fibrosis – the risk of an affected child will vary, depending on the ethnicity,
for CF is more prevalent in persons from northern Europe. Parental CF carrier
testing can detect 80% of obligate carriers when parents are of northern
European background, but this is lower in other ethnic groups. If both parents
are carriers, definitive prenatal diagnosis is available.
• Maternal initial and convalescent titres look for fetal infections.
(CMV, herpes simplex, toxoplasmosis, parvovirus B19, varicella)
• Detailed fetal ultrasound at 19-24 weeks to look for other structural anomalies
and for evidence of bowel obstruction/perforation, and at 30-32 weeks. If the
finding is persistent at the later ultrasound, or if there is IUGR or a GI anomaly,
newborn pediatric consultation is needed.
• Alpha Thalassemia screening of parents in Oriental families
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References:
Soft Fetal Ultrasound Findings
Page 19
Benacerraf BR. (2005). The role of the second trimester genetic sonogram in screening
for fetal Down syndrome. Semin Perinatolo 29: 386-394
Bethune M. (2007). Literature review and suggested protocol fror managing ultrasound
soft markers for Down syndrome: Thickened nuchal fold, echogeneic bowel, shortened
femur, shortened humerus, pyelectasis and absent or hypoplastic nasal bone.
Australasian Radiology 51:218-225.
Carcopino X. et al. (2007). Foetal magnetic resonance imaging and echogenic bowel.
Prenat Diagno 27: 272-278.
Nyberg, et al., (1996). Echogenic fetal bowel during the second trimester: significance
and implications for management. AM. J. Obstet Gynecol 173:1254-87.
Slotnick RN et al., (1996). Fetal echogenic bowel: quantification and prospective
evidence of fetal risk. Lancet 347:85.
Lam YH, et al., (1999). Echogenic bowel in fetuses with homozygous alpha
thalassemia – 1 in the first and second trimesters. Ultra Obstet Gynecol 14(3):180-182.
Kesrouani AK et al.(2003). Etiology and outcome of fetal echogenic bowel. Fetal
Diagnosis and Therapy 18:240-246.
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11. SHORT FEMUR LENGTH February 2008
A short femur length is defined as either a measurement below the 2.5 th percentile for
gestational age or a measurement that is less than 0.9 multiples of that predicted by the
measured BPD. The relationship between bone length and head size may differ across
racial groups.
Natural History:
• Likely normal variant of stature
• Keep in mind ethnic differences in stature
Associations:
• associated with an increased risk of trisomy 21 (stronger if humeri are short too)
• if severely shortened or presence of bowing, fractures, or reduced mineralization
may be an initial sign of a skeletal dysplasia
• occasionally an initial sign of IUGR
Management:
• Ultrasound - If gestation is < 18 weeks, suggest another 18-20 week ultrasound to
assess bone growth. Other long bones should be assessed. Since there can be
late detection of a skeletal dysplasia, another ultrasound around 23 weeks could be
considered if there are persistent concerns on the 18-20 week ultrasound.
• Patient can consider amniocentesis
References:
Benacerraf BR. (2005). The role of the second trimester genetic sonogram in screening
for fetal Down syndrome. Semin Perinatolo 29: 386-394
Bethune M. (2007). Literature review and suggested protocol fror managing ultrasound
soft markers for Down syndrome: Thickened nuchal fold, echogeneic bowel, shortened
femur, shortened humerus, pyelectasis and absent or hypoplastic nasal bone.
Australasian Radiology 51:218-225.
Nyberg DA et al., (1993). Humerus and femur length shortening in detection of Down's
syndrome. Am J Obstet Gynecol 168:534-8.
Shipp TD et al. (2001). Variation in fetal femur length with respect to maternal race. J
Ultrasound Med 20:141-144
Shipp TD et al., (2002). Prenat Dx 22:296-307
Snijders RJM et al. (2000). Femur length and trisomy 21: impact of gestational age on
screening efficiency. Ultrasound Obstet Gynecol 16:142-145
20

Soft Fetal Ultrasound Findings
Page 21
12.SHORT HUMERUS LENGTH February 2008
A short humerus length is defined as either a measurement below the 2.5 th percentile
for gestational age or a measurement that is less than 0.9 multiples of that predicted by
the measured BPD. The relationship between bone length and head size may differ
across racial groups.
Natural History:
• Likely normal variant of stature
• Keep in mind ethnic differences in stature
Associations:
• Associated with an increased risk of trisomy 21
• if severely shortened or presence of bowing, fractures, or reduced mineralization
may be an initial sign of a skeletal dysplasia
• occasionally an initial sign of IUGR
Management:
• Ultrasound - If gestation is < 18 weeks, suggest another 18-20 week ultrasound to
assess bone growth. Other long bones should be assessed. Since there can be
late detection of a skeletal dysplasia, another ultrasound around 23 weeks could be
considered if there are persistent concerns on the 18-20 week ultrasound.
• Patient can consider amniocentesis
References:
Benacerraf BR. (2005). The role of the second trimester genetic sonogram in screening
for fetal Down syndrome. Semin Perinatolo 29: 386-394
Bethune M. (2007). Literature review and suggested protocol fror managing ultrasound
soft markers for Down syndrome: Thickened nuchal fold, echogeneic bowel, shortened
femur, shortened humerus, pyelectasis and absent or hypoplastic nasal bone.
Australasian Radiology 51:218-225.
Kalelioglu IH. (2006): Humerus length measurement in Down syndrome screening. Clin
Exp Obstet Gynecol. 34:93-5.
Nyberg DA et al., (1993) Humerus and femur length shortening in detection of Down's
syndrome. Am J Obstet Gynecol 168:534-8.
Shipp TD et al., (2002) Prenat Dx 22:296-307
21

ULTRASOUND FINDING
Increased nuchal
translucency
ASSOCIATED
CHROMOSOME
ABNORMALITY
• T21
• T18
• 45,X
• Other
Absent nasal bone • T21
• Lower
for
others
Choroid Plexus Cyst T18
OTHER POSSIBLE
UNDERLYING
DIAGNOSIS(ES) OR
ASSOCIATED FINDINGS
• CHD
• Other structural
• Single gene
• IUD
Ethnicity important NIL
NIL NIL
Drooping choroid Nil known ?Prelude to
ventriculomegaly
Mild Cerebral
Ventrriculomegaly
Any • Hydrocephalus
• Other syndromes
Soft Fetal Ultrasound Findings
Page 22
IN ADDITION TO AMNIO
FOR KARYOTYPE
• Detailed u/s
• Echo
Follow-up U/S
• Congenital infection
titres
• Follow up U/S
Enlarged cistern magna Unlikely • U/S at 21-23 weeks
gestation
• MRI
Nasal bone hypoplasia Unclear NIL
Increased nuchal fold • T21
• Other
• CHD
• Single gene
• Other
Echo
Echobright Cardiac
Focus
T21 NIL NIL
Single umbilical artery T21 • Malformation of
kidney, heart , GI, limb
• Follow-up U/S
• IUGR
Renal Pyelectasis T21
• obstructive uropathy Follow up U/S
• VUR
Echogenic Bowel • T21,
• Other
• Structural GI
abnormality
• CF
• Congenital infection
• IUGR
• Intrauterine death
• alpha thalassemia
• CF carrier testing
• Congenital Infection
Titres
• U/S
• alpha thal screen in
Orientals
Short femur/humerus • T21 • Skeletal Dysplasia • Follow-up U/S
22