An echogenic yolk sac is an indeterminate finding in first-trimester fetal ultrasound. It differs from a calcified yolk sac, in that the contents of the yolk sac are echogenic, not just the rim.
One study has suggested that this finding is associated with fetal demise, but other reports in the ...
Ectopia cordis is an extremely rare congenital malformation where the heart is located partially or totally outside the thoracic cavity. The four main ectopic positions are::
adjacent to the thorax: ~60 %
The estimated ...
Ectopic pregnancy refers to the implantation of a fertilised ovum outside of the uterine cavity.
The overall incidence has increased over the last few decades and is currently thought to affect 1-2% of pregnancies. The risk is as high as 18% for first trimester pregnancies with bl...
Ectrodactyly (also known as a split hand-split foot malformation, cleft hand or lobster claw hand) is a skeletal anomaly predominantly affecting the hands (although the feet can also be affected). The condition has a highly variable severity.
The estimated incidence is at ~ 1 in 9...
Ectrodactyly-ectrodermal dysplasia-clefting (EEC) syndrome is a rare genetic syndrome that has high clinical variability but typically comprises of the triad of
ectrodactyly +/- syndactyly 1 +/- polydactyly 5
facial clefts: cleft lip and/or palate
Edwards syndrome, also known as trisomy 18, along with Down syndrome (trisomy 21) and Patau syndrome (trisomy13), make up the only three trisomies to be compatible with extra-uterine life in non-mosaic forms, albeit in the case of Edward syndrome only for a week or so.
An embedded intrauterine contraceptive device is a situation where there is a an abnormally positioned IUCD within the endometrium or myometrium; however without an extension through the serosa. The IUCD should be removed in this situation. An IUCD can become embedded in the wall of the uterus o...
An embryo is a term given to a precursor of a fetus and in humans the term is usually considered to be between the first and the eighth week of development after fertilisation. The term "fetal pole" is sometimes used synonymously with the term embryo. Following this period, the term fetus is use...
Embryonic growth discordance is a term given to a twin growth discordance occurring during the early embryonic period. It is principally manifested by a discrepancy in crown rump length. It can be a relative common finding in early twin pregnancies with the mean discrepancy according to one stud...
The empty amnion sign is a sonographic observation where there is the visualization of an amniotic sac without concomitant visualization of an embryo. It is an indicator of pregnancy failure regardless of the mean sac diameter and is considered to have a sufficiently high positive predictive val...
Empty gestational sacs can be due to a number of causes:
anembryonic pregnancy (also known as "blighted ovum")
early pregnancy (intrauterine): by 5.5 weeks gestational age, a yolk sac should be identifiable by transvaginal ultrasound
pseudogestational sac with an ectopic pregnancy
Encephalocoele, also known as meningoencephalocele, is a form of neural tube defect and a type of cephalocoele where brain tissue and overlying meninges herniate out through a defect in the cranium.
It should be distinguished from cranial meningocele in which the lesion contains o...
Endometrial reflectivity grading on ultrasound is a system initially proposed by Smith et al in 1984 which classifies the endometrium into four types according to the echotexture pattern. They are considered to be useful in deciding on receptivity in in-vitro fertilisation (IVF).
The Smith syst...
Endometrial thickness is a commonly measured parameter on routine gynaecological ultrasound and MR imaging. The appearance, as well as the thickness of the endometrium, will depend on whether the patient is of reproductive age or post-menopausal and, if of reproductive age, at what point in the ...
Enlarged echogenic fetal kidneys can be associated with a number of pathologies that include:
autosomal recessive polycystic kidney disease (ARPKD) 1
autosomal dominant polycystic kidney disease (ADPKD) 3: the large cysts may not form in utero and the kidneys may initially appear as enlarged a...
Epignathus is a term given to a very rare form of teratoid tumour that arises from the oropharyngeal region.
There may be a slight female predilection ref. The estimated incidence is ~ 1 in 35,000 to 200,000 births.
The tumour classically presents in utero ...
Identification of fetal skeletal epiphyseal ossification centers on ultrsound can be a useful tool for estimating gestaional age, particularly at a time near fetal lung maturity.
Specifically the distal femoral epipyses (DFE) and the proximal tibial epiphyses (PTE) can be used.
Erb palsy, also known as brachial plexus birth palsy, is a form of obstetric brachial plexus injury as a result of complications during delivery.
The most common cause is due to excessive lateral traction or stretching of the fetal head and neck in opposite directions du...
Ethmocephaly refers to a rare type of midline cranio-facial anomaly that is characterised by the presence of extreme hypotelorism, arrhinia and a midline proboscis.
holoprosencephaly 1-2: particularly alobar holoprosencephaly
Exencephaly is a lethal congenital fetal brain developmental anomaly (neural tube defect) considered to be a precursor to anencephaly in the acrania-exencephaly-anencephaly sequence.
It is characterised by calvarial absence and loss of fetal brain tissue to variable degrees and is co...
The expanded amnion sign has been described as a poor prognostic sign in early pregnancy, suspicious though not diagnostic of failed early pregnancy. An abnormal embryo will have an abnormally large amniotic cavity. Gestational sac diameter is usually found to be correct for age.
Facial clefts comprise of a wide spectrum of pathologies which result from failure of fusion in the facial region during the embryonic - early fetal period. This results is gap in the fetal face. These clefts can affect the lip, philtrum, alveolus and hard and soft palate to varying degrees.
Failed early pregnancy refers to the death of the embryo and therefore, miscarriage. The most common cause of embryonic death is a chromosomal abnormality.
Findings diagnostic of pregnancy failure
crown-rump length (CRL) of ≥7 mm and no heartbeat on a transva...
Failed pregnancy is a pregnancy that will not carry through to term.
It is termed a miscarriage or failed early pregnancy when fetal demise occurs before 20 weeks gestational age and fetal death in utero (FDIU) when it occurs after 20 weeks gestation.
The term "non-viable" pr...
Fallopian tube rupture is most often a complication of a tubal ectopic pregnancy where the pregnancy breaks open due to progressive growth. It can potentially lead to shock.
Factors that raise the risk for a tubal rupture in a given tubal ectopic pregnancy include 2-4:
False umbilical cord knots are commonly formed variants in the umbilical cord anatomy. It basically represents, exaggerated looping of the umbilical cord vessels, causing focal dilatation of the umbilical cord vessels.
bulge or protruberance in the umbilical c...
Fanconi anaemia (FA) is a rare disorder characterised by progressive bone marrow failure, various congenital abnormalities, and predisposition to malignancies (often acute myeloid leukaemia). It is considered the commonest type of inherited marrow failure syndrome 7.
Female pseudohermaphroditism (FPH) is a form of disorder of gender development.
Patients with female pseudohermaphroditism have female internal genitalia and female karyotype (XX) with various degree of external genitalia virilization.
congenital adrenal hyperplasia (CAH) ...
Femur fibula ulna (FFU) syndrome is a rare congenital non lethal anomaly which is classically characterised by unilateral limb defects of the femur and fibular or one limb followed by a contralateral defect in the ulna 2. There has however be several variations including bilateral involvement 4....
Fetal femur length (FL) is one of the basic biometric parameters used to assess fetal size. Femur length together with biparietal diameter, head circumference, and abdominal circumference are computed to produce an estimate of fetal weight. In the second trimester this may be extrapolated to an ...
Femur sparing intrauterine growth restriction is considered by some authors as a particular type of intrauterine growth restriction (IUGR) 1. In this type, the femoral length is the only standard fetal biometric parameter unaffected while all others are reduced.
Abdominal circumference (AC) is one of the basic biometric parameters used to assess fetal size. AC together with biparietal diameter, head circumference, and femur length are computed to produce an estimate of fetal weight. In the second trimester this may be extrapolated to an estimate of gest...
A fetal adrenal haemorrhage is an uncommon occurrence.
The exact cause of adrenal bleeding in utero is not well known at the time of writing. It has been associated with birth trauma (breech birth), perinatal asphyxia, sepsis, and congenital infections (classically syphilis) 8-9.
Fetal akinesia essentially means a complete lack of fetal movement (c.f fetal hypokinesia where fetal movement is less than expected). The significance of detecting fetal akinesia in a live fetus is that it can be associated with a fetal akinesia deformation sequence.
A fetal akinesia sequence (FAS) is an event that can occur with a lack of fetal movement (fetal akinesia). This results in
fetal joint contractures: arthrogryposis
craniofacial anomalies 3
The esimated prevalence is at ~ 1...
Fetal alcohol syndrome (FAS) is a potential syndromic complication that can occur with maternal pre-natal alcohol exposure. It is also broadly categorized as fetal alcohol spectrum disorders (FASD) due to the fact that the fetus may not show all the features and the broad spectrum of effects on ...
Fetal anaemia can result from many causes.
haemolytic disease of the newborn
fetomaternal ABO incompatibility
fetomaternal rhesus (Rh) incompatibility
fetal parvovirus B19 infection
homozygous alpha thalassaemia 7
Fetal anasarca refers to generalised fetal body oedema and usually occurs as a component of hydrops fetalis. The fetal subcutaneous tissues appear diffusely thickened often to more than 5 mm.
It occurs from a fluid shift from the intra-vascular compartment into the interstitial extr...
Fetal anterior abdominal wall defects can occur with a number of pathologies.
limb body wall complex
omphalocoele-radial ray (ORR) complex
Pentalogy of Cantrell
A fetal arteriovenous malformation (FAVM) is essentially an arteriovenous malformation that presenting in utero. They tend to be very different in location to those that commonly occur in children and adults.
fetal intracranial arteriovenous malformations
vein of Galen malformati...
Fetal ascites refers to the accumulation of free fluid in the fetal abdomen. It is often considered under the same spectrum of hydrops fetalis.
any condition that results in hydrops fetalis
additional causes include
bowel perforation (e.g. meconium peritoniti...
Fetal atrial fibrillation is a type of fetal tachyarrhythmia and usually has atrial rate of 400 beat per minute and a completely irregular ventricular rhythm.
Antanatal ultrasound - echocardiography
The artial contractions are usually too faint to be detected by M Mode ...
Fetal atrial flutter is the second most common fetal tachyarrhythmia and can account for up to 30% of such cases 1-2.
As with other tachyarrthymias it is often detected in the 3rd trimester.
It has a typical atrial rate of 300-600 beats per minute (bpm)...
Fetal biometric parameters are antenatal ultrasound measurements that are used to indirectly assess the growth and well being of the fetus.
Assessed and reported on a routine 2nd trimester scan or when growth reassessment is required in the second or third trimester.
Fetal biophysical profile score (BPS or BPP) refers to assessment of four discrete biophysical variables by ultrasound. It is a standard tool in antepartum fetal assessment. It is usually assessed after 28 weeks of gestation.
The ultrasound variables...
Fetal bowel dilatation can occur from many causes, which include:
intestinal atresias: mainly distal
apple-peel intestinal atresia
megacystis microcolon hyperperistalsis syndrome 4
congenital chloride d...
Fetal bradyarrhythmia refers to an abnormally low fetal heart rate (less than 100-110 beats per minute 3,7) as well as being irregular, i.e. irregular fetal bradycardia.
A fetal bradyarrhythmia can fall in to several types which include
fetal partial atrioventricular block (PAVB)
Fetal bradycardia refers to an abnormally low fetal heart rate, a potentially ominous finding. A sustained first trimester heart rate below 100 beats per minute (bpm) is generally considered bradycardic. The average fetal heart rate changes during pregnancy, however, and some consider the lower ...
Fetal brain tumours are uncommon and tends to have very different pathological spectrum than that observed in adults; in order of decreasing frequency:
fetal intracranial teratoma: most common tumour by far
astrocytoma/glioblastoma: next most common
craniopharyngioma: papillary type
Fetal cardiac tumours refer to primary cardiac tumours that can present in the in utero population.
Fetal cardiac tumours are rare; the prevalence, reported from autopsy studies of patients of all ages, varies from 0.0017-0.28 % 2.
Known cardiac tumour types that pres...
Fetal cardiomegaly (FC) essentially refers to an enlarged fetal heart. It is variably defined with some sources stating the cut off as a fetal cardio-thoracic circumference above two standard deviations 7.
It can arise from a number of situations which include
congenital cardiac an...
Fetal cardiomyopathy refers to a very rare situation where a cardiomyopathy occurs in utero. It is often a diagnosis of exclusion where by definition there is an absence of an underlying congenital cardiac morphological anomaly.
The estimated incidence is variable with the high en...
Fetal cardiothoracic (C/T) circumference ratio is a parameter than can be used in assessment of fetal cardiac and thoracic/chest wall anomalies. It is the ratio of the cardiac circumference to the thoracic circumference and may be easily measured on fetal ultrasound/echocardiography.
Fetal choledochal cysts are choledochal cysts diagnosed in utero.
The estimated incidence rate of choledochal cysts is ~1 in 2 million live births 2. There is a recognsed female predilection and a greater occurrence in Asian populations.
Fetal cholelithiasis refers to formation of gallstones in utero.
There occurrence is thought to be relatively common and is estimated at 1 in 300 pregnancies. They are almost always seen in the 3rd trimester 1. There may be slightly greater male predilection 7.
Fetal chylothorax is defined as the presence of lymphatic fluid within the pleural cavity.
may show echogenic fluid in the pleural cavities
Some of the de...
Fetal circulation differs from the adult circulation due to the presence of certain vessels and shunts.
These shunts will close after birth, and most of these fetal vessels will be seen as remnants in the adult circulation. The function of these shunts is to direct oxygen-rich venous blood to ...
Fetal clenched hands are an antenatal ultrasound observation where the fetal hands are in a constant (permanently) clenched position as if being unable to extend.
Some authors 3 suggest that the abnormal posture results in part from:
muscle variations along the radial margin of the...
Fetal colonic dilatation specifically refers to dilatation of the fetal colon - large bowel
This can occur in a number of situations
fetal bowel dilatation
Fetal congenital complete heart block (CAVB) is a rare cardiac conduction abnormality which is associated with high morbidity and mortality. It is considered the commonest of fetal bradyarrhymias.
The estimated prevalence of complete heart block in newborns is at ~1 in 20,000.
There are numerous fetal congenital anomalies associated with maternal diabetes.
cardiac: congenital cardiac anomalies
ventricular septal defect (VSD) 5
transposition of the great arteries (TGA)
fetal congestive cardiac failure (witho...
Fetal cystic renal disease can be in included in three of the four types classified according the system by Osathanondh and Potter 1:
Potter type I: infantile polycystic kidney disease
Potter type II: multicystic dysplastic kidneys
Potter type III: adult polycystic kidney disease
Fetal death in utero (FDIU) is the term used when the death of a fetus occurs after the 20th week of pregnancy. Prior to this, it is considered a miscarriage.
1% of normal, uncomplicated pregnancies end in fetal death. In ~15% of FDIU, no cause is identified.
NB - Please consult original article(s) and discuss with you local radiology department/radiation physicist before making any clinical decision.
Although exposure to the gravid uterus is to be avoided when ever possible, and only deliberately performed after careful weighing up of the pros and ...
Fetal ductus venosus flow assessment can be sonographically assessed in a number of situations in fetal ultrasound:
first-trimester screening for aneuploidic anomalies
second-trimester scanning when there are concerns regarding
intrauterine growth restriction (IUGR)
fetal cardiac compromise
A standard fetal echocardiogram consists of several specific views which can be obtained to optimise visualisation of different structures and anomalies. They include:
abdominal situs view
four chamber view
left ventricular outflow tract view (or a five-chamber view)
Fetal enteric duplication cysts are enteric duplication cysts presenting in utero.
They result from an abnormal recanalisation of the gastrointestinal tract. They comprise of a two-layer smooth muscle wall and an internal epithelium of a respiratory or intestinal type. These cysts ma...
The fetal fibronectin test (fFN) is a test that can be perfomed on a vaginal swab to estimate the risk of preterm labour.
fFN is found at the interface of the chorion and the decidua (between the fetal sack and the uterine lining). It can be thought of as an adhesive or "biological ...
A fetal goitre is an enlargement of the thyroid gland in utero. It can occur with either hyper or hypothyroidism (and in isolated cases of euthyroidism 8).
The mechanism is different depending on whether the underlying cause is hyper or hypothyroidism.
The fetal head sparing theory is one that underpins asymmetrical intra-uterine growth restriction, where the difference between normal head circumference and decreased abdominal circumference is attributed to the fetus's ability to preferentially supply the cerebral, coronary, adrenal and spleni...
Fetal heart beat can be detected as early as 34 days (just under 6 weeks) gestation on good quality, high frequency transvaginal ultrasound, as a crown rump length (CRL) of as little as 1-2 mm.
If a fetal heartbeat cannot be identified with a CRL >7 mm using transvaginal scanning, then embryona...
A normal fetal heart rate (FHR) usually ranges from 120 to 160 beats per minute (bpm) in the in utero period. It is measurable sonographically from around 6 weeks and the normal range varies during gestation, increasing to around 170 bpm at 10 weeks and decreasing from then to around 130 bpm at ...
Fetal hepatomegaly (or more simply an enlarged fetal liver) can occur in number of situations. It can occur with or without fetal splenomegaly.
in utero infections
fetal parvovirus B19 infection
fetal cytomegalovirus infection 3
transient abnormal myelopoiesis (TAM) associate...
Fetal hepatosplenomegaly refers the combined enlargment of both the fetal liver and fetal spleen. This can occur from a number of pathologies which include.
transient abnormal myelopoiesis (TAM) 1-2 associated with trisomy 21
in association with fetal hydrops
in utero infections
The fetal hydantoin syndrome refers to a spectrum of features that can develop in a small proportion (~ 10% 5) of women taking the anti-epileptic drug hydrantoin (Dilantin TM) during pregnancy.
increased risk of intracranial bleeding
Fetal hydrocephalus often refers to an extension of fetal ventriculomegaly where the ventricular dilatation is more severe. It is usually defined when the fetal lateral ventricular diameter is greater than 15 mm 1.
The estimated incidence is 0.5-3% per 1000 live births. There may ...
A fetal hydrocoele refers to an hydrocoele present in utero.
They may be sonographically identified in ~ 15% of male fetuses in the third trimester 6.
Often result from a patent processus vaginalis. They are more frequently unilateral.
Fetal hydronephrosis represents the abnormal dilatation of the fetal renal collecting system, with pelvi-ureteric junction obstruction the most commonly encountered cause.
Please, refer to the article on fetal pyelectasis for a dedicated discussion on this relatively common and usually benign ...
A fetal hydrothorax refers to fluid in the fetal thoracic cavity. In many cases it represents a fetal pleural effusion. In selected cases it can be treated by in utero thoracocentesis or a formation of a in utero pleuro-amniotic shunt.
primary fetal hydrothorax
Fetal hypoxia (FH) (also known as intrauterine hypoxia (IH)) occurs when the fetus is deprived of an adequate supply of oxygen.
Fetal hypoxia can occur from a number of reasons:
umbilical cord prolapse
cord occlusion or cord thrombosis
A fetal interhemispheric cyst refers to an interhemishperic cyst diagnosed in utero. It is seen as a cystic collection located in the interhemispheric fissure, with or without communication with the ventricular system.
agenesis of the corpus callosum: strong association...
Fetal intra-abdominal cystic lesions can arise from a number of entities:
fetal gastric dilatation / fetal stomach bubble (can be pathological if there is a gastric outlet obstruction
normal fetal gallbladder
No colour flow
fetal choledochal cyst
fetal hepatic cyst ...
Fetal intracranial calcification refers to intracranial calcification detected in utero. This can arise from a number of pathologies which include:
in utero infections
fetal toxoplasmosis infection: calcification tends to be randomly distributed
fetal cytomegalovirus infection1: calcificatio...
Fetal intracranial cystic lesions can arise number of pathologies, including:
fetal arachnoid cyst
fetal choroid plexus cyst
fetal connatal cyst
fetal porencephalic cyst
fetal interhemispheric cyst
fetal sub ependymal cyst
dorsal cyst of holoprosencephaly
Blake pouch cyst...
Fetal intracranial haemorrhage may occur either within the cerebral ventricles, subdural space or infratentorial fossa.
Haemorrhages can occur in a number of situations:
mechanical trauma, e.g. maternal abdominal blunt or birth trauma
severe fetal hypoxia
background fetal thromboc...
Fetal intrahepatic calcification can be a relatively common finding. Calcifications in the liver can be single or multiple and in most cases in which isolated hepatic calcific deposits are detected, there is usually no underlying abnormality.
The presence of isolated intrahepatic calcification ...
Fetal limb bowing may be a feature of skeletal dysplasia, particularly if it is severe. A mild degree of lateral bowing to femur can occur as part of normal variation.
Conditions associated with fetal limb bowing include:
camptomelic dysplasia 1
thanatophoric dysplasia 2: particularly type I
Fetal maceration is one of the signs of fetal death. It is a destructive aseptic process that appears between 12 to 24 hours after fetal death. It may not be seen in a pregnancy earlier than 6 months. In this a separation of the skin from head and trunk occurs giving a bubble-like appearance.
Fetal macrosomia (also sometimes termed large for gestational age) is usually defined when the estimated fetal weight (EFW) is greater than the 90th percentile. According to this definition it affects up to 10% of all live births. Some also use an increased birthweight (i.e. greater than 4500g) ...
Fetal MCA systolic/diastolic (S/D) ratio is an important parameter in fetal middle cerebral arterial Doppler assessment. It is a useful predictor of fetal distress and intrauterine growth restriction (IUGR).
During pregnancy the middle cerebral (and other intracranial)...
Fetal megacystis refers to the presence of an unusually large bladder in a fetus.
The estimated incidence of antenatal imaging is at ~1:1500 pregnancies.
It can result from a number of causes but the main underlying mechanism is either a distal stenosis or reflux.
Fetal middle cerebral arterial (MCA) Doppler assessment is an important part of assessing fetal cardiovascular distress, fetal anaemia or fetal hypoxia. In the appropriate situation it is a very useful adjunct to umbilical artery Doppler assessment. It is also used in the additional work up of:
The fetal middle cerebral arterial (MCA) peak systolic velocity (PSV) is an important parameter in fetal MCA Doppler assessment.
The fetal MCA should be sampled~2 mm from the origin of the fetal internal carotid artery and the angle of the ultrasound beam and the directi...