Abdominoschisis refers to a split or in the abdominal wall. Some authors use the term synonymously with a gastroschisis. When the defect continues into the thoracic region it is termed a thoraco-abdominoschisis. A large abdominoschisis is considered part of the limb body wall complex 2.
Abnormally thickened endometrium on imaging may occur for a number of reasons which may be categorised based on whether or not they are related to pregnancy. Aetiologies may also be classified based on whether the patient is premenopausal or postmenopausal.
Non-visualisation of the fetal stomach on ultrasound can occur with various physiological as well as pathological processes. It becomes a significant sonographic observation >14 weeks of gestation (about the time the fetus begins to swallow).
physiological emptying: transient
An absent septum pellucidum may rarely be an isolated finding, or more commonly be seen in association with a variety of conditions.
The septum pellucidum is partly or entirely absent in 2 or 3 individuals per 100,000 in the general population.
An absent septum pelluc...
Antenatal screening of Down syndrome (and other less common aneuploidies) should be available as a routine component of antenatal care. It allows families to either adjust to the idea of having a child with the condition or to consider termination of pregnancy.
For a general description of Down...
Arthrogryposis (multiplex congenita) is a clinical or imaging descriptor that denotes congenital non-progressive joint contractures involving two or more body regions.
It is thought to occur in approximately 1:3000-10,000 live births 6,8.
It can result from a number o...
Beta-hCG (bHCG) is a sex hormone found in the mother's blood serum that can be used to help interpret obstetric ultrasound findings.
Beta-hCG levels may be used in three ways in the clinical setting of pregnancy:
qualitatively, for presence/absence of fetal tissue
more often determined with a...
Birth trauma relates to those conditions caused by both physical/mechanical and hypoxic injuries.
Birth trauma occurs in ~5 per 1000 births 2.
Cervical incompetence refers to a painless spontaneous dilatation of the cervix, and is a common cause of 2nd trimester pregnancy failure.
The estimated incidence varies geographically and generally thought to be around 1-1.5% of all pregnancies 1,15.
Congenital limb amputations are a limb anomaly that usually occur due to disruption of vascular supply.
Congenital amputations occur in 0.5 (range 0.03-1) per 1000 live births 2.
Slightly more common in the upper limb (60%) than in the lower limb (40%) 2.
Congenital renal anomalies comprise of vast spectrum of pathologies and include:
congenital renal hypoplasia
congenital cystic renal disease
infantile polycystic renal disease: autosomal recessive polycystic kidney disease (ARPKD):...
Uterine bleeding during pregnancy is a common clinical presentation that often necessitates obstetric ultrasound for the assessment of the haemorrhage, and of fetal well being.
The potential causes vary with the stage of gestation.
Bleeding in the first trimester
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 labour.
The incidence o...
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
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
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...
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...
Fetal anterior abdominal wall defects can occur with a number of pathologies.
limb body wall complex
omphalocoele-radial ray (ORR) complex
Pentalogy of Cantrell
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 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 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 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 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 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.
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 pleural effusions (FPE) refer to an accumulation of pleural fluid in utero. It can refer to either a fetal chylothorax or a fetal hydrothorax.
A fetal pleural effusion can occur as part of hydrops fetalis, in association with other anomalies without hydrops or in isolation - pr...
Fetal pyelectasis refers to a prominence of the renal pelvis in utero that is a relatively common finding, which in the majority of cases resolves spontaneously.
Please refer to the article on fetal hydronephrosis for a continued discussion on this matter.
Although there is an ...
Fetal rib fractures can be caused by certain skeletal dysplasias. These include:
osteogenesis imperfecta: type II - one of the classical causes of fetal rib fractures
achondrogenesis: type Ia - Houston-Harris sub type
Although rare, a number to tumours may be diagnosed antenatally. These fetal tumours are a diverse and a unique group of conditions, and include:
neuroblastoma: most common tumour overall
head and neck teratoma/epignathus
Fetal ventriculomegaly (ventricle width >10 mm) is an important finding in itself and it is also associated with other central nervous system abnormalities. For more information, see the main article fetal ventriculomegaly.
Fetal ventriculomegaly can be thought of in ter...
Frontal bossing is a calvarial radiographic feature where the front of the skull appears protruding anteriorly. It is best appreciated on a sagittal or lateral image.
This feature can be seen in many conditions (in alphabetical order):
Gonadal dysgenesis refers to a spectrum of anomalies with abnormal development of the gonads. It falls under the even broader group of disorders of gender development.
In many cases the gonads are replaced by fibrous tissue.
complete gonadal dysgenesis (CGD) / Swyer syndro...
Hypotelorism refers to an abnormal decrease in distance between any two organs although some authors use the term synonymously with orbital hypotelorism meaning an abnormal decrease in the distance between the two eyes (the eyes appear too close together). The article mainly focuses on the latte...
Intracranial cystic lesions in the perinatal period can carry a relatively wide differential which includes:
Supratentorial cystic lesions
choroid plexus cyst
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:
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...
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
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 ...
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...
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...
Oligohydramnios refers to a situation where the amniotic fluid volume is less than expected for gestational age. Often these fetuses have <500 mL of amniotic fluid.
The estimated prevalence can be up to ~6% of pregnancies 4.
The causes of oligohydramnios are pr...
Perigestational haemorrhage refers to haemorrhage that occurs around the fetus during the gestational period. The spectrum of haemorrhage includes:
chorionic haemorrhage: caused by the separation of the chorion from the endometrium
subchorionic haemorrhage: most common type, occurs between th...
Phocomelia is an extremely rare congenital skeletal disorder that characteristically affects the limbs. It can affect either the upper limbs or lower limbs or both. Phocomelia is also a descriptive term to describe the characteristic limb anomalies occurring with its associated conditions.
Placentomegaly is a term applied to an abnormally enlarged placenta.
It can be associated with number of maternal and fetal disorders which include:
chronic intrauterine infections
Polyhydramnios refers to a situation where the amniotic fluid volume is more than expected for gestational age.
It is generally defined as:
amniotic fluid index (AFI) > 25 cm
largest fluid pocket depth (maximal vertical pocket (MVP)) greater than 8 cm 6: although some centres particularly in ...
Pregnancy of uncertain viability (PUV) is a term given to an intrauterine pregnancy in a situation where there are not enough criteria (usually on ultrasound grounds) to confidently categorise an intrauterine pregnancy as either viable or a failed pregnancy.
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
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...
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
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 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...
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...
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.
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...
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 ...
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.
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.
Umbilical cord cysts can refer to any cystic lesion associated with the umbilical cord. They can be single (commoner) or multiple.
They may be seen in ~3% of pregnancies in the first trimester 8.
Umbilical cord cysts can represent either true or false cysts:
Uterine enlargement can occur in a number of situations from both diffuse and focal processes. These include:
gestation related events
normal intrauterine pregnancy
molar pregnancy - gestational trophoblastic disease
postpartum uterus - still larger than usual