Retroplacental complex (RPC) is the region behind the placenta and is composed of decidua basalis and portions of myometrium including the maternal veins which drain the placenta.
visualised post 20 weeks of gestation
seen as an echo-poor, subplacental region...
Retroplacental haemorrhage (RPH) occurs when there is perigestational haemorrhage that is confined to the retroplacental space.
This type of haemorrhage occurs behind the placenta. The haematoma therefore separates the placenta from the uterine wall. The source of bleeding is probabl...
Reversal of umbilical artery end-diastolic flow (REDF) or velocity is often an ominous finding if detected after 16 weeks. It is classified as Class III in severity in abnormal umbilical arterial Dopplers 6.
The estimated incidence is at ~0.5% of all pregnancies with a much higher...
Rhizomelic dwarfism is a type of dwarfism where the dominant feature is proximal (i.e. femoral, humeral) limb shortening.
The following conditions fall under the heading of rhizomelic dwarfism 3
rhizomelic chondrodysplasia punctata
The rhombencephalon, or hindbrain is a primary vesicle of the neural tube.
During the fifth week of embryological development the rhombencephalon further subdivides into the secondary brain vesicles, the metencephalon and the myelencephalon 1.
The metencephalon goes on to form th...
The right ventricular outflow tract (RVOT) view (or three vessel view/3VV) is one of the standard views in a fetal echocardiogram.
It is a long axis view of the heart, highlighting the path from the right ventricle into the pulmonary trunk (right ventricular outflow tract).
In this view, the r...
Robert sign refers to the presence of a gas shadow within the heart or the greater vessels, in cases of fetal death in utero. It is a rare sign caused by postmortem blood degeneration, usually seen 1-2 days after death; and may be seen as early as 12 hours.
fetal death in utero
Roberts Syndrome (RBS) (also known as Roberts-SC phocomelia syndrome, pseudothalidomide syndrome, Appelt-Gerken-Lenz syndrome) is rare congenital malformation syndrome. It has an autosomal recessive inheritance.
intrauterine growth restriction (IUGR)
Robinow syndrome is a rare heterogenous genetic disorder with at least two distinct forms.
The syndrome can affects several systems which include:
mesomelic limb shortening: mesomelia
characteristic facies anomalies
A rocker bottom foot (also known as a congenital vertical talus) is a congenital anomaly of the foot. It is characterised by a prominent calcaneus/heel and a convex rounded sole.
It results from a dorsal and lateral dislocation of the talonavicular joint.
Rothmund-Thomson syndrome (RTS) is an extremely rare autosomal recessive disorder with heterogeneous clinical features.
It is characterized by many features which include:
poikiloderma: characteristic rash, typically develops in infancy
sparse hair, eyelashes, and/or eyebro...
Rubinstein-Taybi syndrome (RTS) is a very rare genetic multi-system disorder primarily characterised by mental retardation, broad and often angulated thumbs and halluces, and distinctive facial features.
The estimated incidence is 1 in 100,000-125,000 live births 5.
Ruptured omphalocoele occurs when there is rupture of the outer membrane of an omphalocoele. When this happens the eviscerated fetal bowel looks free floating and distinction from gastroschisis becomes difficult. However the abdominal defect generally tends to be larger and may contain liver wit...
A rupture of membranes (ROM) or amniorrhexis is a term used during pregnancy to describe a rupture of the amniotic sac. This can occur as part of normal birth (or "spontaneously") if it occurs at full term at the onset of, or during, labor. It is also colloquially known as "breaking water."
Russell-Silver dwarfism is a very rare syndrome characterised by:
intrauterine growth restriction: tends to give an asymmetrical IUGR
postnatal growth restriction
relatively large calvarium: pseudohydrocephalus
clinodactyly/clinobrachydactyly of the small finger
a typical triangular type fa...
Sacrococcygeal teratoma (SCT) refers to a teratoma arising in the sacrococcygeal region. The coccyx is almost always involved 6.
It is the commonest congenital tumour in the fetus 11 and neonate 3. The incidence is estimated at ~1:35000-40000. There is recognised female predilecti...
SADDAN syndrome is an acronym for (severe achondroplasia with developmental delay and acanthosis nigricans). It is an extremly rare condition and as the name stands comprises of skeletal brain and cutaneous anomalies.
It (like achondroplasia) also results from a mutation i...
The Sakati-Nyhan syndrome, also known as Sakati-Nyhan-Tisdale syndrome or acrocephalosyndactly type III, is an extremely rare type of acrocephalopolysyndactyly.
Its main features include:
congenital limb abnormalities
congenital heart defects
History and etymology
A sandal gap deformity is an imaging observation in antenatal ultrasound (typically second trimester) where there is an apparent increase in the interspace between the great toe of the foot from the rest of the toes (likened to the gap caused by a sandal).
While it can be a normal variant (esp...
Scar endometriosis is a term given to endometriosis occurring in a Caesarian section scar. It can be located at the skin, subcutaneous tissue, rectus muscle/sheath, intraperitoneally, or in the uterine myometrium (within uterine scar).
The reported incidence of abdominal scar endo...
Schizencephaly is a rare cortical malformation that manifests as a grey matter lined cleft extending from the ependyma to the pia mater.
Some authors do not use the term schizencephaly, preferring to group these disorders under the blanket term of porencephaly. For the purpose of t...
Seckel syndrome is an autosomal recessive congenital dwarfing disorder.
The estimated incidence is ~ 1:10,000. There is no recognised gender predilection.
It is clinically characterised by many features including
intrauterine growth restriction (IUGR)
The second trimester scan is a routine ultrasound examination in many countries that is primarily used to assess fetal anatomy and detect the presence of any fetal anomalies.
The second trimester extends from 13 weeks and 0 days to 27 weeks and 6 days of gestation although the majority of thes...
Semilobar holoprosencephaly is a subtype of holoprosencephaly (HPE) characterised by an incomplete forebrain division. It is intermediate in severity, being worse than lobar holoprosencephaly and better than alobar holoprosencephaly.
Please refer on the general article of holopros...
Shorted fetal femur is a morphological descriptor and is usually defined when the femoral length falls below the 5th centile for gestational age (some define it when its under the 2.5th centile 5) or less than 0.91 predicted by the bi-pareital diameter. It can occur in isolated or in association...
Shortened fetal humerus is a morphological description and is usually defined when the humeral length falls below the 5th percentile or less than 0.9 predicted by the bipareital diameter (BPD). It can occur in isolation or in association with a number of other anomalies.
The humeral length is n...
Shortened fetal long bones (SFLB) can involve either the upper limb and / or the lower limb. It is borad descriptive entity which can include
short fetal femur
short fetal humerus
short fetal tibia - fibula
short fetal radius - ulna
the presence of shorted fetal lon...
Shortening of the uterine cervical canal as the name implies refers to an abnormal shortening of the uterine cervical length. It is considered a sign of cervical incompetence in pregnancy and can lead to premature delivery.
primary (i.e. congenital/idiopathic)
A short maxillary length can result from many congenital and acquired causes. If seen in an antenatal ultrasound scan, it is often considered to have a high association with trisomy 21 1.
Many conditions that can cause midfacial hypoplasia will result in a short maxillar...
Short rib polydactyly syndrome(s) (SRPS) comprise of a rare group of severe osteochondrodysplasias. There are four major recognised types present:
type I: Saldino-Noonan type
type II:: Majewski type
type III: Verma-Naumoff type
type IV: Beemer-Langer type
There may also be other very rare t...
SHORT syndrome refers to an acronym which primarily comprises of the following features:
S: short stature
H: hyperextensibility of joints and/or inguinal hernia
O: ocular depression
R: Rieger anomaly
T: teething delay
In a addition to these there can be numerous associated minor features w...
Short umbilical cord has been variably defined. Considering the mean length of the umbilical cord is 50-70 cm 1-2, a short cord in absolute terms is usually taken as one that is under 35-40 cm in length at term 1-2.
Recognised associations include
Simple hydropic degeneration of the placenta is a form hydropic degeneration of the placenta that can occur in a first trimester pregnancy loss. In this situation the serum beta HCG will tends to be low and would show a decline.
The overal sonographic appearance can vary dependant on the degree...
Single umbilical artery (SUA) results when there is a congenital absence of either the right or left umbilical artery. In the usual situation, there are paired umbilical arteries. For some unknown reason, the absence of the left umbilical artery is much more common (~70%).
Sirenomelia (also known as the mermaid syndrome) is a rare congenital malformation characterised by the fusion of lower limb structures.
The estimated incidence is at ~1 in 60,000-70,000 of pregnancies 9. There may be greater male predilection (somewhat paradoxical given the usage...
Skeletal dysplasias (osteochondrodysplasias) refer to an abnormality in bone formation. There is a very wide clinicopathological spectrum and any part of the skeleton can be affected.
The overall prevalence is estimated at ~2 per 10,000 live births 3.
At least 3...
A small for dates fetus can result from a number of factors
structural anomalies (syndromes)
fetal Warfarin syndrome
hydantoin embryopathy (Dilantin TM)
A small gestational sac in early first trimester is considered a poor prognostic factor. Some authors use the mean sac diameter to crown rump length difference of 5 mm or greater to be normal 1.
The smaller than expected sac diameter in pregnancies 36-42 days from the last menstrual period ha...
A small placenta if observed on antenatal ultrasound can arise from a number of situations. They include:
variation in placental morphology: where only part of the placenta is seen
bilobed placenta: with only one lobe seen
succenturiate lobe: with either main lobe or succenturiate lobe not se...
A small yolk sac is considered a non-specific feature and, at the time of writing, there are not many publications about the clinical importance of small yolk sacs.
According to some publications, a very small yolk sac may be a normal finding during early periods of normal embryologic developme...
Smith-Lemli-Opitz syndrome (SLOS) also known as 7-dehydrocholesterol reductase deficiency is an inborn error of cholesterol synthesis.
The estimated incidence is at 1:20000-40000 live births. Prevalence may be greater in Nordic countries.
The condition often results f...
Snake under the skull sign is a vascular anomaly seen in holoprosencephaly.
Due to the defect in the cleavage of the two hemispheres there is a fusion of the frontal lobes. This band of abnormal cortical tissue causes forward displacement of the anterior cerebral artery, so that it l...
Snowstorm sign in obstetric imaging is classically seen in complete hydatiform mole. It is characterised by the presence of many hydropic villi which gives the ultrasonographic appearance of a central heterogeneous mass having a solid, hyperechoic area and interspersed with a multitude of cystic...
Snowstorm sign may refer to:
snowstorm sign: complete hydatiform mole (ultrasound)
snowstorm sign: extracapsular breast implant rupture (ultrasound)
Obstetric and gynaecological ultrasound is rampant with numerous cut off values. Some of these get revised over the years. The following list is a useful aid to refer to and revise.
rate of increase of a mean sac diameter per day in early pregnancy
generally accepted value for a th...
The Spalding sign refers the overlapping of the fetal skull bones caused by collapse of the fetal brain. It appears usually a week or more after fetal death in utero.
This finding was originally described on abdominal radiographs and is indicative of fetal demise.
The spectrum of abnormal placental villous adherence describes the degree to which there is an invasion of chorionic villi into the myometrium because of a defect in the decidua basalis.
Placental villous adherence is classified on the basis of depth of myometrial invasion:
Spina bifida is a type of neural tube defect/spinal dysraphism which can occur to varying degrees of severity. It is often considered the most common congenital CNS malformation.
The estimated incidence is at 1:1000-2000 live births 2.
A constellation of fe...
Spinal dysraphism is a broad term given to a group of anomalies where there are malformations in the dorsum of the embryo. Neural tube defects come under this group as well.
There is often abnormal fusion of the midline embryonic neural, vertebral and mesenchymal structures.
Spondylocostal dysostosis (SCDO) is a rare condition characterised by short-trunk dwarfism secondary to developmental anomalies of the vertebrae and ribs. Previously the condition Jarcho-Levin syndrome (also known as spondylothoracic dysostosis) was grouped together with spondylocostal dysostosi...
A spontaneous rupture of membranes (SROM) refers to a rupture of fetal membranes occuring on its own (c.f artificial rupture of membranes). When this occurs prior to ~ 37 weeks in gestation, it is then termed spontaneous premature rupture of membranes (SPROM) which it the usual cause of pre-term...
Stenosis of the uterine cervix is the pathologic narrowing of the uterine cervix. The term cervical stenosis is clinically defined as cervical narrowing that prevents the insertion of a 2.5 mm wide dilator.
If the stenosis is severe enough it may result in proximal obstru...
Stickler syndrome refers to a group of disorders primarily affecting connective tissue.
Several gene mutations have been idntified dependent on specific sub types which include:
Stickler syndrome type I: COL2A1
Stickler syndrome type II: COL9A1
Stickler syndrome type III: COL11A1
Straight umbilical cord implies, as the name suggests, an umbilical cord with no coils.
The reported incidence of a straight cord is about 3.7-5% of all pregnancies.
the entire length of the umbilical cord shows no evidence of coiling
Strawberry skull refers to the shape of the head on an antenatal ultrasound.
In general, strawberry skull is considered one of the nonspecific 'soft markers' for abnormal fetal development. It is considered more closely associated with trisomy 18 (Edward syndrome).
Subamniotic haemorrhage is considered a type of perigestational haemorrhage.
Subamniotic haematomas are classical placental pathological lesions resulting from the rupture of chorionic vessels (allantochorionic vessels) close to the cord insertion.
A subamniotic hemorrhage is conta...
Subchorionic cyst is often considered a subtype of placental surface cyst (commonest type). They are often multiple and may be present in ~5-7% of term placentas 2. Occasionally they can compress chorionic or amniotic vessels leading to adverse fetal outcome.
Subchorionic haemorrhage (SCH) occurs when there is perigestational haemorrhage and blood collects between the uterine wall and the chorionic membrane in pregnancy. It is a frequent cause of first and second trimester bleeding.
It typically occurs within the first 20 weeks of gest...
Subgaleal haematoma describes scalp bleeding in the potential space between the periosteum and the galea aponeurosis.
It most commonly occurs after vacuum assisted delivery, but may also be seen following head trauma. In patients with intracranial haemorrhage or skull fractures, the incidence o...
A succenturiate lobe is a variation in placental morphology and refers to a smaller accessory placental lobe that is separate to the main disc of the placenta. There can be more than one succenturiate lobe.
The estimated incidence is ~2 per 1000 pregnancies.
Symmetrical intrauterine growth restriction is a type of intrauterine growth restriction (IUGR) where all fetal biometric parameters tend to be less than expected (below the 10th percentile) for the given gestational age. Both length and weight parameters are reduced.
Please, refer to the artic...
Syndactyly refers to a congenital fusion of two or more digits. It may be confined to soft tissue (soft tissue syndactyly / simple syndactyly) or may involve bone (bony syndactyly / complex syndactyly).
The overall estimated incidence is at ~1 per 2500 to 5000 live births 6,8. The...
Syntelencephaly, also known as middle interhemispheric variant (MIHV), is a mild subtype of holoprosencephaly that is characterized by an abnormal midline connection of the cerebral hemispheres between the posterior frontal and parietal regions.
Syntelencephaly is a congenital ma...
TAR syndrome stands for thrombocytopaenia with absent radius and as the name implies is primarily characterised by the following two features:
absent fetal radii (bilaterally) with the presence of both thumbs
The condition is extremely rare with an estima...
Terminal myelocystoceles are an uncommon form of spinal dysraphism representing marked dilatation of the central canal of the spinal cord, herniating posteriorly through a dorsal spinal defect. The result is a skin-covered mass in the lower lumbar region, consisting of an ependyma-lined sac.
Thalidomide embryopathy refers to a syndrome resulting from in utero exposure to thalidomide, and is characterized by multiple fetal anomalies. Fetal exposure to thalidomide occurred primarily from 1957 to 1961, when it was used as a treatment for nausea in pregnant women.
Theca lutein cysts (TLC), also known as hyperreactio luteinalis (HL), are a type of functional ovarian cysts. They are typically multiple and seen bilaterally.
They are thought to originate due to excessive amounts of circulating gonadotrophins such as beta-hCG. Hyperplasia of the th...
Thoracopagus conjoined twins are, as the name suggests, conjoined twins united at their thorax.
Fusion is typically face-to-face, at the upper thorax to the umbilicus with a common sternum, diaphragm, and upper abdominal wall. Very often a common pericardial sac is present as well as a degree o...
Threatened miscarriage (or threatened abortion) is mainly a clinical term, used when a pregnant woman in first 20 weeks of gestation presents with spotting, mild abdominal pain and contractions, with a closed cervical os.
It occurs in 20-25% of pregnancies and is associated with ...
The three vessel and trachea view (or 3VT view) is one of the fetal echocardiography views. In this view, aortic and ductal arches are combined into the DAo and appear as a V-shaped confluence. Both arches tend to be of similar size and are located towards the left of the trachea. The thymus is ...
Tracheal atresia (TA) is an extremely rare anomaly and refers to a congenital absence of the trachea.
There may be a greater male predilection 5.
Tracheal atresia falls under the spectrum of laryngeal-tracheo-bronchial atresia which in turn results either from an obstr...
Transient abnormal myelopoiesis (TAM) is a phenomenon that can happen in the fetuses or neonates with trisomy 21. The condition can mimic leukaemia.
The estimated incidence is at ~10% of newborns with trisomy 21 3.
In the context of kn...
In obstetric imaging, the fetal transverse cerebellar diameter (TCD) is often measured as an additional fetal biometric parameter. It is measured as the maximal diameter between the cerebellar hemispheres on an axial scan. The value of the transverse cerebellar diameter in mm's is considered rou...
Trauma is a leading cause of mortality in pregnancy. Pregnancy increases the incidence and severity of abdominal trauma in females.
Trauma affects up to 7% of pregnancies, and the incidence of pregnancy in level 1 trauma patients is estimated to be ~2% 1.
The traumatic abruption placenta scale (TAPS) was devised to stratify placental injury findings on CT. Since placental abruption is a concern in a pregnant patient who has undergone traumatic injury, CT is occasionally the first imaging modality used to evaluate the placenta.
0: normal homogene...
A trident hand is a description where the hands are short with stubby fingers, with a separation between the middle and ring fingers.
It can be seen in various chondrodysplasias including achondroplasia.
Triple screening refers to a screening blood test that is used to screen pregnant women for possible neural tube defects, Down syndrome and trisomy 18 in the developing baby. It measures:
An abnormal test result doesn't indica...
Triploidy is a rare lethal chromosomal (aneupliodic) abnormality caused by the presence of an entire extra chromosomal set.
It is considered the 3rd commonest fatal chromosomal anomaly 7. While it is thought to affect as much as 1-2% of conceptions, the vast majority are thought ...
Trisomies are chromosomal anomalies which usually occur due to non-disjunction. The vast majority of affected fetuses being spontaneously aborted, often very early during gestation. Only three are compatible with extra-uterine life (T13, T18, T21), and only one beyond early infancy (T21).
Trisomy 22 is an aneuploidic chromosomal anomaly which is usually fatal unless in mosaic forms.
Duplication of the short arm (p) and a small section of the long arm (q) of chromosome 22 can give result to the cat-eye syndrome - Schmidt-Fraccaro syndrome.
True umbilical cord knots are a rare occurrence and as the name suggests represent a knot formation in the umbilical cord.
They occur in less than 1% of pregnancies.
a long umbilical cord
excessive fetal movements.
The "T sign" is really the absence of a twin-peak sign (or lambda sign) and is used in ultrasound assessment of a mulifetal pregnancy.
It refers to the lack of chorion extending between the layers of the intertwin membrane, denoting a monochorionic pregnancy. The intertwin membrane comes to an ...
Tubal ectopic pregnancy (or adnexal ectopic pregnancy) is the most common location of an ectopic pregnancy.
It is the most common type of ectopic by far, accounting for 93-97% of cases.
Although the fallopian tube has many anatomical parts, for the purposes of ectopic ...
Tubal ring sign, also referred to as bagel sign or blob sign, one of the ultrasound signs of a tubal ectopic. It comprises of an echogenic ring which surrounds an unruptured ectopic pregnancy. It is said to have a 95% positive predictive value (PPV) for ectopic pregnancy.
Turner syndrome, also referred as 45X, is the most common of sex chromosome abnormalities in females.
The incidence is estimated at 1:2000-5000 of live births, although the in utero rate is much higher (1-2% of conceptions) due to a significant proportion of fetuses with 45X abor...
The twin anaemia polycythaemia sequence (TAPS) is considered a variant of the twin to twin transfusion syndrome (TTTS).
TAPS may occur spontaneously in up to 5% of monochorionic twins and may also develop after incomplete laser treatment in TTTS cases 2.
As with TTTS t...
The twin embolisation syndrome (TES) is a rare complication of a monozygotic twin pregnancy following an in utero demise of the co-twin.
It was traditionally thought to result from the passage of thromboplastic material into the circulation of the surviving twin which causes ischemic...
In obstetric imaging, twin growth discordance refers to a significant size or weight difference between the two fetuses of a twin pregnancy. To be classified as a growth discordance, some consider that the estimated fetal weight (EFW) of the smaller twin should fall under the 10th centile.
A twin growth disparity is a closely related term to twin growth discordance. In a twin growth disparity, there may be a significant size or weight difference between the two fetuses but estimated fetal weight of smaller twin does not fall below the 10th centile. ( In contrast to twin growth dis...
The twin peak sign (also known as the lambda (λ) sign) is a triangular appearance of the chorion insinuating between the layers of the inter twin membrane and strongly suggests a dichorionic twin pregnancy. It is best seen in the first trimester (between 10-14 weeks). 5 While the presence of a t...
Twin pregnancies are the most common multifetal pregnancies.
Multifetal pregnancies account for ~ 1% of all pregnancies, but are seen in much higher numbers in populations where in vitro fertilisation (IVF) is a common practice, most of which are twin pregnancies.
Twin reversed arterial perfusion (TRAP) sequence is considered a severe variant of the twin to twin transfusion syndrome (TTTS). The hallmark of this condition which only happens in monochorionic pregnancies is the lack of placental perfusion of one of the twins (so called acardiac twin), with a...
Twin to twin transfusion syndrome (TTTS) is a potential complication that can occur in a monochorionic twin (either MCDA or MCMA) pregnancy.
This complication can occur in ~10% (range 15-25%) of monochorionic pregnancies giving an estimated prevalence of ~1:2000 of all pregnancie...