Inter twin membrane folding is an observation where the inter twin membrane in a twin pregnancy appears as being folded. It is sometimes used as a predictor for the development of twin to twin transfusion syndrome. It occurs as a result of amniotic fluid discordance.
Some reports suggest that ...
Intracranial cystic lesions in the perinatal period can carry a relatively wide differential which includes:
Supratentorial cystic lesions
choroid plexus cyst
Intradecidual sac sign (IDSS) is a useful feature in identifying an early intrauterine pregnancy (IUP) as early as 25 days of gestation 1. The threshold level (earliest one can see the sign) is 24 days of gestation and the discriminatory level (one should always see the sac) is 47 days. As per t...
Intramembranous ossification describes the process of ossification from mesenchymal cells (stem cells) without a cartilaginous template and is involved in the healing process of fractures. The stages of intramembranous ossification osteogenesis are as follows:
mesenchymal cells differentiate in...
The presence of intrauterine air can sometimes be inferred by tiny internal echoes on ultrasound or foci of very low attenuation at computed tomography (CT). The term encompasses air within the uterine cavity as well as intramyometrial air.
It can arise from a number of situations
Intrauterine blood clot can result from a number of situations in gravid, non-gravid and postpartum states. It can mimic many other pathologies.
Any condition that predisposes to an intrauterine haemorrhage can potentially result in an intrauterine blood clot.
Intra-uterine contraceptive devices (IUCD) are one of the most frequently used methods of contraception throughout the world. It prevents pregnancy by:
thinnning the endometrial lining
preventing sperm motility
There are two main types of IUCDs:
Intrauterine growth restriction (IUGR) is commonly defined as an estimated fetal weight (EFW) at one point in time during pregnancy being at or below the 10th percentile for gestational age 2.
Some authors define the term IUGR when fetal biometric parameters fall under the 5th percentile or fal...
An echogenic membrane might be seen within the uterus during pregnancy
membrane of maternal origin
membrane of fetal origin
In utero bowel perforation results in a chemical peritonitis (meconium peritonitis) from peritoneal leakage of sterile meconium.
It can result from many causes which include:
in utero intestinal ischaemia
In utero herpes simplex infection usually occurs from transplacental tramission of the herpes simplex virus. Transplacental intrauterine infection with herpes simplex virus is an
extremely rare complication of primary herpes simplex in pregnancy.
Fetal HSV infection much less c...
In utero infections, also known as congenital infections, can result from a vast number of aetiological organisms and account for 2% to 3% of all congenital anomalies 4.
in utero toxoplasmosis infection / congenital toxoplasmosis infection:
congenital cerebral toxoplasmosis
In utero syphilis infection, or congenital syphilis, results from transplacental transmission of the maternal infection from the spirochete Treponema pallidum, subspecies pallidum.
For a general discussion, and for links to other system specific manifestations, please refer to the article on s...
An in utero varicella zoster virus infection is an infrequent type of in utero infection. The clinical features can be diverse and variable depending on the stage of gestation.
Fetal infection with varicella is unusual in the current age due to most women of childbearing age being...
Invasive mole is a tumorous growth associated with gestation and falls under the spectrum of gestational trophoblastic disease. Due to their aggressive growth characteristics, invasive moles are considered locally invasive non-metastasising neoplasms.
An invasive mole develops in ...
An irregular gestational sac as the name suggests is a gestational sac which does not have the well defined, regular borders of a normal gestational sac. It is an imaging feature related to a non-viable pregnancy.
irregular yolk sac
An irregular yolk sac or an abnormally shaped yolk sac is an imaging feature that can be observed in early pregnancy scanning. It may be seen in up to 17% of early pregnancy scans 1. In contrast to an irregular gestational sac, the observation of an irregular yolk sac in not thought to correlate...
An isolated cleft palate is a type of facial cleft. This is a much rarer occurrence than a cleft lip +/- palate and is thought to represent a different pathological entity.
The estimated incidence is at ~1 per 2000-2500 pregnancies 4-5. There may be a slight female predilection 4....
An isthmic ectopic pregnancy is a sub type of tubal ectopic pregnancy an accounts for ~ 12% of such cases. According to one study the rate of tubal wall disruption was higher than with an ampullary ectopic pregnancy, suggesting that in an isthmic ectopic pregnancy, the trophoblast penetrates the...
IUCD related uterine perforations are one of the causes of uterine perforation. It is rare, but a serious complication of an IUCD insertion, and is often clinically silent.
The incidence rate is reported at ~2 in 1000 2.
Perforation at the time of insertio...
The Jarcho-Levin syndrome (JLS) or spondylothoracic dysostosis is a rare autosomal recessive heterogeneous disorder which can occur to variable severity. Previously the condition spondylocostal dysostosis was also considered as part of the JLS spectrum but is now considered a distinct pathologic...
Juberg-Hayward syndrome (JHS), also known as the oro-cranio-digital syndrome, is a rare autosomal recessive syndrome characterised by the association of the following:
cleft lip and palate
minor vertebral and rib anomalies 4
horseshoe kidneys 4
Kinking of the brainstem is a rare finding in fetal or pediatric neuroimaging, invariably seen in association with other cerebral abnormalities. It generally heralds a poor neurological outcome.
A kinked brainstem may be seen on fetal MRI, commonly after referral from ul...
There are a number of lambda signs:
lambda sign of twin pregnancy
lambda sign of sarcoidosis
A large for date uterus is a clinical observation based on uterine fundal height, which may result in referral for ultrasound assessment, usually in mid to late pregnancy.
constitutionally large fetus
Large loop excision of the transformation zone (LLETZ) is a gynaecological procedure. It is currently one of the most commonly used approaches to treat high grade cervical dysplasia - cervical intraepithelial neoplasia.
A large yolk sac is one measuring >5-6 mm in pregnancies between a gestational age of 5-10 weeks. One study had shown that a yolk sac diameter of >5 mm can be associated with an increased risk of spontaneous miscarriage although few other authors have mentioned the existence of a very large yolk...
Larsen syndrome (LS) is an extremely rare disorder, often classified as a type of osteochondrodysplasia.
The estimated incidence is thought to be at ~ 1 in 100,000 people. There may be an increased female predilection.
It is characterised by many features i...
The left ventricular outflow tract (LVOT) view (or five chamber view) is one of the standard views in a fetal echocardiogram.
It is a long axis view of the heart, highlighting the path from the left ventricle into the ascending aorta (left ventricle outflow tract).
In this view the right ventr...
The lemon sign, noted on antenatal imaging, is one of the many notable fruit inspired signs. It is a feature when there appears to be an indentation of the frontal bone (depicting that of a lemon). It is classically seen as a sign of a Chiari II malformation and also seen in the majority (90-98%...
Lethal multiple pterygium syndrome (LMPS) is a lethal sub type of the multiple pterygium syndrome.
It is primarily characterised by the presence of pterygia (or wings) present in two or more body areas overlying predominantly the large joints. Accompanying joint contractures are almo...
Lethal omphalocele-cleft palate syndrome is, as the name suggests, characterised by the association of omphalocele and cleft palate.
Prevalence is assumed to be <1 per 1,000,000. It has been postulated that this syndrome is likely to be an autosomal recessive condition 1.
History and etymolog...
Lethal skeletal dysplasias form a heterogeneous group which are commonly characterised being non-survivable for prolonged periods ex-utero. They include:
chondrodysplasia punctata: lethal variants
metatropic dysplasia: lethal variants 4...
The limb-body wall complex (LBWC) is a rare variable group of congenital limb and body wall defects (involving mainly the chest and abdomen). They can include:
abdominoschisis: usually large and left-sided 4, and almost always present
thoracic wall defect / thoracoschisis
Lithopaedions, also referred as stone babies, are a rare phenomenon which occurs most commonly when a fetus dies during an ectopic pregnancy.
The estimated incidence is at ~ 1.5 to 1.8% of abdominal ectopic pregnancies 4.
If the dead fetus is too large to be re-absorbe...
A live ectopic pregnancy is an ectopic pregnancy where a live extrauterine fetus can be demonstrated.
Loeys-Dietz syndrome (LDS) is an autosomal dominant genetic syndrome which has many features similar to Marfan syndrome.
The syndrome features a classical triad of 1:
arterial tortuosity and aneurysms
bifid uvula or cleft palate
It is caused by mutations in the gene...
A long philtrum is a clinical or imaging observation where the philtrum (middle part of the upper lip) is longer than normal.
It can be associated with a number of anomalies which include
Cornelia de Lange syndrome
A long umbilical cord has been variably defined. Considering the mean length of the umbilical cord at ~50-70 cm 1, a long cord in absolute terms is usually taken as one that is over 70 cm in length at term 1-3.
increased incidence of umbilical cord knots
increased incidence of ...
Lowe syndrome (also known as the the oculocerebrorenal syndrome of Lowe) is a multi-system disorder characterised by anomalies primarily affecting the eyes, nervous system, and kidneys.
It is an extremely rare, pan-ethnic, x-linked disease, with estimated prevalence in the general po...
Low-lying placenta occurs when the placenta extends into the lower uterine segment and its edge lies too close to the internal os of the cervix, without covering it. The term is usually applied when the placental edge is within 0.5-5.0 cm of the internal cervical os 1. Some alternatively give th...
Low set ears is a descriptive term used to given a depressed or abnormally low positioning of the pinna by two or more standard deviations below the population average.
Low set ears can be associated with a number of anomalies which include
aneuploidic / chromosomal sy...
The lying down adrenal sign is a feature seen usually associated with renal agenesis or renal ectopia. It is an important antenatal sonographic sign.
On an antenatal ultrasound scan, the adrenal of the affected side appears flattened, elongated, and lying along the spine due to absence of the ...
Macroglossia means an enlarged tongue. It may be absolute (greater than the 95th centile) or relative (enlarged compared with oral cavity).
Recognised associations include:
tends to be a relative macroglossia
may also have intermi...
Marginal cord insertion is a type of abnormal cord insertion.
The estimated incidence is at ~7% 1 of singleton pregnancies but ~25% of twin pregnancies. Hence, it is very important to locate the umbilical cord in all patients, particularly in high risk pregnancy.
Marginal placental abruption is the most common type of placental abruption wherein a haematoma is seen as the name suggests in the margin of the placenta and the blood collects below the chorionic membrane. It is most often seen in placentae that are partially implanted in the lower uterine seg...
Marshall-Smith syndrome (MSS) is a rare genetic syndrome primarily comprising of the triad of facial dysmorphism, failure to thrive and accelerated osseous maturation 5. Many cases however have wider clinical spectrum.
overgrowth - fetal macrosomia
failure to thriv...
Maternal hydronephrosis in pregnancy often results as a physiological phenomenon due to the presence of the fetus.
It is estimated that up to 90 percent of women have some degree of asymptomatic dilatation of the renal calyces, the renal pelves and the upper two-thirds of the ure...
McKusick Kaufman syndrome (MKS) is an autosomal recessive multiple malformation syndrome primarily characterised by
hydrometrocolpos - vaginal atresia
congenital heart disease
Mean sac diameter (MSD) is a sonographic measurement of the gestational sac which is usually first seen at around 3 weeks after conception (5 weeks after the last menstrual period), when it measures 2-3 mm.
MSD = (length + height + width)/3
Normal MSD (in mm) + 30 = days of pregnancy
Role of ...
Meckel-Gruber syndrome (MGS) is classically characterised by the triad of:
renal cystic dysplasia: multiple renal cysts (present most cases)
occipital encephalocoele / holoprosencephaly (~70%)
postaxial polydactyly: usually hexadactyly (~65%)
Additional hepatic developmental defects and hepa...
Meconium pseudocyst formation is a complication that can occur with meconium peritonitis.
It occurs when the extruded meconium becomes walled off within the peritoneal space.
May be seen as a rim calcified mass within the abdomen.
Megacystis microcolon intestinal hypoperistalsis syndrome (MMIHS) (also known as the Berdon syndrome) is a rare congenital disorder characterised by a dilated non-obstructive urinary bladder and hypoperistalsis of the gastrointestinal tract.
There is recognised strong female predi...
Megalencephaly (MEG) is a disorder characterised by an abnormally large brain. It is primarily a proliferative disorder of embryonic origin. It may involve all or part of the cerebral hemispheres and can be bilateral or unilateral. It is often associated with polymicrogyria or agyria.
Mendelson syndrome or peptic pneumonia refers to acute chemical pneumonitis caused by the aspiration of stomach contents in patients under general anesthesia.
The etiologic agents is believed to be aspiration of acidic stomach contents, other compounds, e.g. bile, may also play a rol...
Mesoblastic nephroma, also sometimes known as a congenital mesoblastic nephroma (CMN) or fetal renal hamartoma, is, in general, a benign renal tumour that typically occurs in utero or in infancy.
It is the commonest neonatal renal tumour. Diagnosis is usually made in the antenatal...
Mesomelia refers to a shortening of the middle (intermediate) portion of a limb.
mesomelia-synostoses syndrome (MSS) or mesomelic dysplasia with acral synostoses1
Ellis van-Creveld syndrome 2
Metatrophic dysplasia is a rare group of skeletal dysplasia. It is part of the wider category of rhizomelic dwarfism. Disorders in this group include:
lethal metatropic dysplasia (type 2) or hyperchondrogenesis
lethal hyperplastic metatropic dysplasia (type 1)
Microcephaly is a descriptive term meaning a small head and is associated with numerous disorders of diverse aetiology. It is usually associated with microencephaly (small brain). For the purpose of this article the two will be used interchangeably.
As with most terms which describ...
Microgenia is a term meaning a small chin. It is somewhat related to but let distinct from the term micrognathia which means a small mandible.
Microgenia can be isolated or be associated with a numer of anomalies which include
camptomelic dysplasia 1
The term micrognathia essentially means a small mandible.
A small mandible occurs secondary to abnormalities of the first branchial arch which in turn are caused by deficient or insufficient migration of neural crest cells and usually occur around the 4th week of gestation.
Microphthalmia essentially means small eyes. It is characterised by a small eye within a small orbit. It can be unilateral or bilateral. It is sometimes defined as a globe with a total axial length (TAL) that is at least two standard deviations below the mean for age.
Midfacial hypoplasia is a type of congenital facial anomaly and can be feature of a number of congenital syndromic anomalies. These include:
chromosome 1p36 deletion syndrome 2
chromosome 18q deletion syndrome
fetal alcohol syndrome
fetal valproate s...
Miller-Dieker syndrome (MDS) or is a rare chromosomal anomaly and is one of the conditions considered part of lissencephaly type I (classic) 6.
neuronal migrational anomalies: lissencephaly type I
prominent subarachnoid spaces
widened cerebral v...
Mirror syndrome or triple oedema or Ballantyne syndrome is a rare disorder affecting pregnant women. It refers to the unusual association of fetal and placental hydrops with maternal pre-eclampsia and oedema.
History and etymology
It was first described in 1892 by John William Ballantyne.
A miscarriage is the spontaneous termination of a pregnancy before 20 weeks gestation.
The term miscarriage is preferred by many over 'abortion' due to the use of the latter for therapeutic pregnancy termination, and the perceived stigma attributed to it by some.
A missed miscarriage, sometimes termed a missed abortion 3, is a situation when there is a non-viable fetus within the uterus, without symptoms of a miscarriage.
Ultrasound diagnosis of miscarriage should only be considered when either a mean gestation sac d...
Mixed gonadal dysgenesis (MGD) is a type of gonadal dysgenesis characterised by gonadal asymmetry, and/or sex chromosomal mosaicism, as well as retained Müllerian ducts.
Depending on the chromosomal composition, patients may have testes and/or streak gonads.
A monochorionic diamniotic (MCDA) twin pregnancy is a subtype of monozygotic twin pregnancy. These fetuses share a single chorionic sac but have two amniotic sacs and two yolk sacs.
It accounts for the vast majority (~70-75%) of monozygotic twin pregnancies although only ~30% of ...
A monochorionic monoamniotic (MCMA) twin pregnancy is a subtype of monozygotic twin pregnancy. These fetuses share a single chorionic sac, a single amniotic sac and, in general, a single yolk sac.
It accounts for the minority (~5%) of monozygotic twin pregnancies and ~1-2% of al...
A monochorionic twin pregnancy is a type of monozygotic twin pregnancy where the twins share a single chorion. Depending on the sharing of the amnion this can be divided into two types.
monochorionic monoamniotic (MCMA) pregnancy: single amnion
monochorionic diamniotic (MCDA) pregnancy: two am...
A mono nostril falls under the midline facial defects which arise from cleavage anomalies. It can occur as part of many underlying conditions such as
holoprosencephaly: particularly alobar holoprosencephaly
Several other facial anomalies can be associated ...
A monozygotic (MZ) twin pregnancy results from division of single zygote following fertilisation and share similar genetic materials. These twins are therefore always of the same gender.
MZ twins account for approximately 30% of all twin pregnancies 1. The estimated incidence is a...
Müllerian duct anomalies (MDAs) are congenital abnormalities that occur when the Müllerian ducts (paramesonephric ducts) do not develop correctly. This may be as a result of complete agenesis, defective vertical or lateral fusion, or resorption failure.
MDAs are estimated to occur...
Multiple placental cystic spaces can be seen in many conditions:
within the placenta
true placental cysts
allantoic ducts cysts
hydropic degeneration of placenta
placental mesenchymal dysplasia
adjacent the placenta
The multiple pterygium syndrome(s) (MPS) refers to a group of disorders which are collectively characterised by multiple soft tissue webs (or pterygia) across the neck and various joints.
They can be broadly classified into two main groups
lethal multiple pterygium syndrome
non lethal multipl...
MURCS association refers to the combination of:
MU: Müllerian duct aplasia
R: renal aplasia /renal agenesis
CS: cervicothoracic somite dysplasia
Myelomeningocoele, also known as spina bifida cystica, is a complex congenital spinal anomaly that results in spinal cord malformation (myelodysplasia).
It is one of the commonest congenital CNS anomalies and thought to occur in approximately 1:500 of live births 5. There may be ...
The Naegele's formula is simple arithmetic method for calculating the EDD (estimated date of delivery) based on the LMP (last menstrual period).
To the date of the first day of the LMP (e.g. 22nd June 2008):
add seven days (i.e 29th)
subtract 3 months (i.e March)
add one year (i.e 2009)
The Nager syndrome (also known as acrofacial dysostosis) is a rare congenital syndrome primarily characterised by facial and skeletal features
There may be agenetic defect localized to chromosome 9q32. Most cases are thought to be sporadic . Occasional autosomal recessive a...
A narrow fetal thorax on antenatal ultrasound can be present with a number of anomalies which include:
Jeune syndrome - asphyxiating thoracic dysplasia
short rib polydactyly syndr...
Neu-Laxova syndrome is a lethal autosomal recessive multiple malformation syndrome with a heterogeneous phenotype.
The clinical spectrum can be quite wide and includes:
dermal / cutaneous
severe skin restriction
decreased fetal movement
marked intrauterine gro...
Neural tube defect (NTD) refers to the incomplete closure of the neural tube in very early pregnancy.
The neural tube comprises of a bundle of nerve sheath which closes to form brain at the anterior end and spinal cord at the posterior end. The closure should occur at around the 28th day of co...
The neurenteric canal or canal of Kovalevsky is the transient communication of the amnion through notochordal canal to the yolk sac during notochordal formation at day 16-17.
Abnormalities during this stage produce the neurenteric cyst spectrum.
The Noack syndrome is a type of acrocephalopolysyndactyly. It is now considered a variant of the Pfeiffer syndrome 2.
Non-gestational choriocarcinoma is choriocarcinoma occurring in the absence of a preceding gestation. As opposed to a gestational choriocarcinoma, this is a much rarer situation.
In women they often tend to occur in ovary. Most ovarian non-gestational choriocarcinomas occur in mixed...
Non-invasive perinatal testing (NIPT) is an antenatal screening technique which has relatively recently come into practice. It relies on the detection of small amounts of cell free fetal DNA to be detected in the maternal bloodstream, hence allowing prenatal genetic diagnosis to occur by way of...
Non visualisation of the fetal gallbladder is often a transient finding and in most bases can be eventually detected. However it can be rarely associated with certain pathological conditions.
agenesis of the gallbladder
Noonan syndrome (NS) is a genetically and phenotypically heterogenous non aneuploidic congenital RASopathy. Affected individuals can bear some clinical features similar to that of Turner syndrome.
The estimated incidence is at ~1 in 1000-2500 11. As individuals have normal number...
Noonan syndrome with multiple lentigines, previously known as LEOPARD syndrome (LS), is a rare autosomal dominant RASopathy that has many similarities to Noonan syndrome.
Despite a change in formal name, the 'LEOPARD' acronym is still useful to summarise the clinical feat...
A nuchal cord (NC) is a term given to situation where there are one or more loops of umbilical cord wrapped around the fetal neck for ≥360°.
The prevalence is dependent on the extent of coiling and range from ~25% for a single loop to 2.5% for a double loop to ~0.5% for more than ...
Nuchal fold thickness is a parameter that is measured in a second-trimester scan (at ~18-22 weeks) and should not be confused with nuchal translucency (which is measured in the first trimester).
The proposed aetiology of increased nuchal thickness is the result of congenital heart di...
Nuchal translucency is a finding during a specific period in the late first trimester and early second trimester (11.3-13.6 weeks) and should not be confused with the nuchal thickness, which is measured in the second trimester.
Increased nuchal translucency is thought to be related t...