A dichorionic diamniotic (DCDA) twin pregnancy is a type of twin pregnancy where each twin has its own chorionic and amniotic sacs. This type occurs most commonly with dizygotic twins, but may also occur with monozygotic twin pregnancies. This type of pregnancy may have characteristic findings o...
A dichorionic triamniotic (DCTA) triplet pregnancy is a type a multifetal pregnancy where two of the triplets are monochorionic. This type of pregnancy can carry a unique set of complications.
A dichorionic twin pregnancy is a type of twin pregnancy characterized by two chorions. They are always dichorionic-diamniotic but can be either monozygotic (~11%) or dizygotic (~88%).
Uterine bleeding during pregnancy is a common clinical presentation that often necessitates obstetric ultrasound for the assessment of the hemorrhage, and of fetal well being.
The potential causes vary with the stage of gestation.
Bleeding in the first trimester
A dizygotic (DZ) twin pregnancy is a type of twin pregnancy where two separate ova are independently fertilised by two separate sperm resulting the two separate zygotes. These twins are also known as fraternal twins or non-identical twins. They may or may not be of the same gender.
A dominant ovarian follicle refers to the follicle that enlarges to release an ovum during a menstural cycle. Usually approximately 10 Graafian follicles begin to mature where one becomes a dominant follicle and the rest become atretic ovarian follicles. After release of the ovum the remainder o...
The dorsal cyst of holoprosencephaly is a large cerebrospinal fluid cavity present in holoprosencephaly that occupies the area above the dorsocaudal aspect of the diencephalon. This communicates directly with the prosencephalic, telencephalic, or diencephalic ventricle. This cavity usually abuts...
A double bleb sign is a sonographic feature where there is visualization of a gestational sac containing a yolk sac and amniotic sac giving an appearance of two small bubbles 2. The embryonic disc is located between the two bubbles. It is an important feature of an intrauterine pregnancy and thu...
The double decidual sac sign (DDSS) is a useful feature on early pregnancy ultrasound to confirm an early intrauterine pregnancy (IUP) when the yolk sac or embryo is still not visualized. It consists of the decidua parietalis (lining the uterine cavity) and decidua capsularis (lining the gestati...
Double outlet left ventricle (DOLV) is an extremely rare congenital cardiac anomaly where both the aorta and pulmonary trunk arise from the anatomical left ventricle. It is usually classified as a conotruncal anomaly and is often associated with a ventricular septal defect with normal continuity...
Duane radial ray syndrome (DRRS) (also known as the Okihiro syndrome) is a rare an autosomal dominant condition characterized by radial ray defects and a Duane anomaly (a form of strabismus with horizontal gaze palsy).
Dubowitz syndrome (DS) is a rare genetic disorder with a wide clinical spectrum which includes:
intrauterine growth restriction (IUGR)
postnatal growth restriction
moderate intellectual disability
characteristic facial anomalies
The ductus arteriosum (DA) (or arteriosus) is the thick short conduit for blood to bypass the non-ventilated lungs in the fetus. It is located between and connects the proximal left pulmonary artery and the undersurface of the aortic arch distal to the origin of the last branch of the arch, at t...
Ductus venosus (DV) is a narrow, trumpet-shaped vessel which is seen in the fetal liver connecting the umbilical vein directly to the caudal inferior vena cava. The vessel plays a critical role in the fetal circulation by shunting oxygenated and nutrient-rich umbilical venous blood from the plac...
The term dystocia in obstetrics means a "difficult birth"
There can be many types of dystocia which include
Shoulder dystocia (SD) refers to the failure of the shoulder to be delivered during childbirth and the need for extra-obstetric maneuvers to facilitate their passage after normal smooth gentle downward traction has failed. Dystocia literally means difficult labor.
The incidence of...
Early pregnancy roughly spans the first ten weeks of the first trimester.
0-4.3 weeks: no ultrasound findings
possible small gestational sac
possible double decidual sac sign (DDSS)
possible intradecidual sac sign (IDSS)
An early structural scan is a first-trimester obstetric scan performed around 12-16 weeks gestation. It can have some similarity to the 11-13 week antenatal scan and assess limited fetal anatomy. A formal assessment of nuchal translucency is, however, not part of this scan.
Echogenic amniotic fluid can potentially arise from a number of entities which include
vernix caseosa : commonest cause
hemorrhage into amniotic cavity
However according to some studies 2 pathological analysis of echogenic appearing fluid had reveal normal amniotic flu...
Echogenic fetal bowel is an observation in antenatal ultrasound imaging, in which fetal bowel appears to be brighter than it is supposed to be. It is a soft marker for trisomy 21 and has several other associations. When observed, it needs to be interpreted in the context of other associated abno...
Echogenic fetal lung lesions on antenatal ultrasound can be detected in a number of situations. They include:
Airway obstructions: lung are often enlarged and echogenic bilaterally
congenital high airways obstruction syndrome (CHAOS)
congenital tracheal stenosis
Echogenic intracardiac focus (EIF) is a relatively common sonographic observation that may be present on an antenatal ultrasound scan.
They are thought to be present in ~4-5% of karyotypically normal fetuses. They may be more common in the Asian population 5.
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 ...
Eclampsia is a condition involving seizures and hypertension in pregnancy. It is thought to result from hypertensive encephalopathy 1.
MR imaging has shown that cytotoxic edema and posterior reversible encephalopathy syndrome are common in eclampsia. The severity of ...
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 incidence is ...
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 (trisomy 13), make up the only three autosomal trisomies to be compatible with extrauterine 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 is considered independent of the chorionicity of the twins 5.
Embryonic growth discordance...
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
Encephalocele, also known as meningoencephalocele, is a form of neural tube defect and a type of cephalocele 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 onl...
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 sys...
Endometrial thickness is a commonly measured parameter on routine gynecological ultrasound and MRI. The appearance, as well as the thickness of the endometrium, will depend on whether the patient is of reproductive age or postmenopausal and, if of reproductive age, at what point in the menstrual...
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 tumor 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 tumor classically presents in utero or...
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 characterized by the presence of extreme hypotelorism, arhinia 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 characterized 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. Any visible embryo that is surrounded by an amnion (visible on transvaginal ultrasound) should also have a heartbeat, regardless of crown-rump len...
Facial clefts comprise a wide spectrum of pathologies that result from failure of fusion in the facial region during the embryonic/early fetal period. The result is a 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...
The eponym Fallopian may refer to:
Fallopian canal (facial nerve canal)
Fallopian tube (uterine duct)
Fallopian ligament (inguinal ligament)
History and etymology
It is named after Gabriele Falloppio (also known by his Latin name Fallopius), Italian anatomist (1523-1562).
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 an exaggerated looping of the umbilical cord vessels, causing focal dilatation of the umbilical cord vessels.
bulge or protuberance in the umbilical ...
Fanconi anemia is a rare disorder characterized by progressive bone marrow failure, various congenital abnormalities, and predisposition to malignancies (often acute myeloid leukemia). Bone marrow failure usually results in decreased production of all blood cells. It is considered the commonest ...
Female pseudohermaphroditism (FPH) is a form of disorder of gender development.
Patients with female pseudohermaphroditism have female internal genitalia and female karyotype (46 XX) with various degree of external genitalia virilization.
congenital adrenal hyperplasia (CA...
Femur fibula ulna (FFU) syndrome is a rare congenital non-lethal anomaly which is classically characterized by unilateral limb defects of the femur and fibula of one limb followed by a contralateral defect in the ulna 2. There have however been several variations described including bilateral in...
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...
Fetal adrenal hemorrhage is an uncommon occurrence and must be differentiated from other lesions especially neuroblastoma.
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 asphyxi...
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 anemia is a characterized by inadequate erythrocytes being delivered to the fetus and can result from many causes.
hemolytic disease of the newborn
fetomaternal ABO incompatibility
fetomaternal rhesus (Rh) incompatibility
fetal parvovirus B19 infe...
Fetal anasarca refers to generalized fetal body edema 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 extra...
Fetal anterior abdominal wall defects can occur with a number of pathologies.
limb body wall complex
omphalocele-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 peritonitis...
Fetal atrial fibrillation is a type of fetal tachyarrhythmia and usually has an atrial rate of 400 beats per minute and a completely irregular ventricular rhythm.
Antenatal ultrasound - echocardiography
The atrial contractions are usually too faint to be detected by M M...
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 tachyarrhythmias, it is often detected in the 3rd trimester.
It has a typical atrial rate of 300-600 beats per minute (bpm) and...
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 into 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 tumors 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 tumor by far
astrocytoma/glioblastoma: next most common
craniopharyngioma: papillary type
Fetal cardiac tumors refer to primary cardiac tumors that can present in the in utero population.
Fetal cardiac tumors are rare; the prevalence, reported from autopsy studies of patients of all ages, varies from 0.0017-0.28 % 2.
Known cardiac tumor types that present ...
Fetal cardiomegaly (FC) 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:
congenital cardiac anomalies: particularly
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 ...
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 of the fetus.
may show echogenic fluid in the pleural cavities
Fetal circulation differs from the adult circulation due to the presence of certain vessels and shunts.
These shunts close after birth, and most of the fetal vessels are visible as remnants in the adult circulation. The function of these shunts is to direct oxygen-rich venous blood to the syst...
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 that 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), also known as intrauterine death (IUD), 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 c...
NB - Please consult original article(s) and discuss with your local radiology department/radiation physicist before making any clinical decision.
Although radiation exposure to the gravid uterus is to be avoided whenever possible, and only deliberately performed after careful weighing up of the...
Fetal ductus venosus flow assessment can be useful 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
Of all the pre-ca...
A standard fetal echocardiogram consists of several specific views which can be obtained to optimize visualization of different structures and anomalies. They include:
abdominal situs view / transverse view of abdomen
four chamber view
left ventricular outflow tract view (or a fi...
Fetal enteric duplication cysts are enteric duplication cysts presenting in utero.
They result from an abnormal recanalization 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 labor.
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 g...
A fetal goiter 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 depends on whether the underlying cause is hyper- or hypothyroidism.
maternal Graves disease with...