Human AFP (alpha-fetoprotein) reduction is seen in pregnancy where it can be associated with:
certain chromosomal anomalies
Cornelia de-Lange syndrome 2
Asymmetrical intrauterine growth restriction is a type of intrauterine growth restriction (IUGR) where some fetal biometric parameters are disproportionately lower than others, as well as falling under the 10th percentile. The parameter classically affected is the abdominal circumference (AC).
Bladder exstrophy (also known as ectopia vesicae) refers to a herniation of the urinary bladder through an anterior abdominal wall defect. The severity of these defects is widely variable.
The estimated incidence of bladder exstrophy is 1:10,000-50,000 live births 4,6. There is a ...
Caesarean scar ectopic pregnancy (CSEP) is a rare type of abnormal implantation. It is often considered the rarest type of ectopic pregnancy, although some do not include it in this category as implantation occurs within the uterus.
It has an estimated incidence of ~1:1800-2200 pr...
Cardiac rhabdomyomas are a type of benign myocardial tumour and are considered the most common fetal cardiac tumour. They have a strong association with tuberous sclerosis.
Cardiac rhabdomyomas are often multiple and can represent up to 90% of cardiac tumours in the paediatric pop...
Cephalocoele refers to the outward herniation of CNS contents through a defect in the cranium. The vast majority are midline.
The estimated incidence is 0.8-4:10,000 live births 13 with a well recognised geographical variation between sub-types. These may be a greater female predi...
Cephalohaematomas are traumatic subperiosteal haematomas of the skull that are usually caused by birth injury. They are bound by the periosteum and, therefore, cannot cross sutures. Being bound by a suture line distinguishes them from subgaleal haematoma, which can cross sutures.
Cephalopelvic disproportion (CPD) occurs when there is a mismatch between the size of the fetal head and the maternal pelvis causing a difficulty in the safe passage of the fetus through the birth canal.
Cephalopelvic disproportion may be caused by the fetal head outgrowing the capac...
Chiari III malformation is an extremely rare anomaly characterized by a low occipital and high cervical encephalocele with herniation of posterior fossa contents, that is, the cerebellum and/or the brainstem, occipital lobe, and fourth ventricle.
agenesis of the corpus...
Chondrodysplasia punctata (CDP) is a collective name for a heterogenous group of skeletal dysplasias. Calcific stippling of cartilage and peri-articular soft tissues is often a common feature.
It can be broadly divided into rhizomelic and non-rhizomelic forms:
Choriocarcinoma is an aggressive, highly vascular tumour. When it is associated with gestation, it is often considered part of the spectrum of gestational trophoblastic disease; it is then termed gestational choriocarcinoma. When it occurs in the absence of preceding gestation, it is termed non-...
Antenatal choroid plexus cysts are benign and are often transient typically resulting in utero from an infolding of the neuroepithelium.
They should not be confused with adult choroid plexus cysts (which are very commonly found at autopsy and likely degenerative), large intraventricular simpl...
Complete hydatidiform mole with coexistant fetus (CHMCF) is an extremely rare entity where as the name suggests there is a twin pregnancy with a complete hydatidiform mole and a normal fetus.
It is seen extremely rarely, with an estimated incidence of one in 22,000–100,000 pregna...
Congenital talipes equinovarus (CTEV) is considered the most common anomaly affecting the feet diagnosed on antenatal ultrasound.
While some use CTEV and club foot (CF) synonymously, in certain publications term clubfoot is considered a more general descriptive term that describes ...
Cystic hygroma, also known as cystic or nuchal lymphangioma, refers to the cystic variety of congenital lymphangioma which, most commonly, occur in the cervicofacial regions, particularly at the posterior cervical triangle.
They usually occur in the fetal/infantile and paediatri...
Dandy-Walker variant (DWv) is a less severe posterior fossa anomaly than the classic Dandy-Walker malformation (DWM) and is considered being on the lesser end of the disease spectrum in the Dandy-Walker continuum.
This term was created to include those malformations that do not mee...
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...
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 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 ...
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 ...
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...
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.
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 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 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 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 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 chylothorax is defined as the presence of lymphatic fluid within the pleural cavity .
may show echogenic fluid in the pleural cavities
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...
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.
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 parvovirus B19 infection is a type of in utero infection. In certain cases it can lead to intra-uterine fetal death.
It was first reported to be associated with fetal death and hydrops fetalis in 1984. Human parvovirus B19 is the only known parovirus virus pathogenic to human...
Fetal pericardial teratomas are rare pericardial teratomas that present in utero. They are an uncommon primary cardiac tumour occurring in a fetus.
It is a type of germ cell tumour and arises from multipotential cells derived from all three germinal layers. In contrast to ovarian ter...
Forked umbilical cord is rare anomaly of the umbilical cord, which can be detected on antenatal scan. The umbilical cord splits into two cords and contains three vessels in each of the bifurcated cords. This anomaly is seen associated with monochorionic twins.
Gastroschisis refers to extra-abdominal herniation (evisceration) of fetal or neonatal bowel loops (and occasionally portions or the stomach and or liver) into the amniotic cavity through a para-umbilical abdominal wall defect.
The estimated incidence is at around 1-6 per 10,000...
Gestational choriocarcinoma (GC) is a type of choriocarcinoma that follows a gestational event. Similar to choriocarcinomas in general, it lies at the malignant end of the spectrum of gestational trophoblastic disease.
Approximately 50% of gestational choriocarcinomas arise from a pr...
Hemimegalencephaly is a rare congenital disorder of cortical formation with hamartomatous overgrowth all or a part of a cerebral hemisphere. This results from either increased proliferation or decreased apoptosis (or both) of developing neurons 2.
Hemimegalencephaly is a cryptogen...
Hydatidiform moles are one of the most common but benign forms of gestational trophoblastic disease.
It is a common complication of gestation, estimated to occur in one of every 1,000-2,000 pregnancies 3. These moles can occur in a pregnant woman of any age, but the rate of occur...
Hydrops fetalis is excessive extravasation of fluid into the third space in a fetus which could be due to heart failure, volume overload, decreased oncotic pressure, or increased vascular permeability. Hydrops fetalis is defined as accumulation of fluid +/- oedema involving at least two fetal co...
An incarcerated uterus or trapped uterus describes an extremely rare situation where a retroverted or retroflexed gravid uterus fails to ascend into the abdominal cavity.
This is an uncommon presentation and is said to occur in 1 in 3000 pregnancies. Uncomplicated retroversion may...
Incomplete miscarriage is a term given to miscarriage where there are retained products of conception still within the uterus.
Ultrasound appearance is variable, ranging from visible fetal parts to a mass of mixed echogenicity. The presence of a prominent vasc...
Interstitial ectopic pregnancy (also known as an intramural) is an important type of ectopic pregnancy with higher risks of rupture and haemorrhage compared to usual tubal ectopic pregnancies.
The term interstitial pregnancy is sometimes interchangeably used with cornual pregnancy...
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...
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...
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...
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...
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.
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 ...
An oesophageal atresia refers to an absence in contiguity of the oesophagus due to an inappropriate division of the primitive foregut into the trachea and oesophagus. This is the most common congenital anomaly of the oesophagus.
It is thought to occur in ~1:3000-4500 live births ...
An omphalomesenteric duct cyst is a type of true umbilical cord cyst.
The omphalomesenteric duct serves as a communication between the midgut and yolk sac In early embryonic life and usually obliterates between the 9-18th week of gestation. The omphalomesenteric duct cyst is an embry...
Ovarian ectopic pregnancies are rare (1-3%) when compared to other types of ectopic pregnancy such as tubal ectopic.
Risk factors include pelvic inflammatory disease, IUCD use and endometriosis. Pathogenesis is debated and lies between:
fertilisation of the ovum in th...
Partial hydatidiform mole (PHD) is a sub type of a hydatidiform mole which in turn falls under the spectrum of gestational trophoblastic disease.
Clinical signs and symptoms such as abdominal pain, cramps of the lower abdomen and vaginal bleeding during pregnancy are non...
Parturition-induced pelvic instability is a rare condition seen in women following vaginal delivery.
The incidence of symphyseal rupture after vaginal delivery ranges from one in 600 to one in 30,000 deliveries 1.
Predisposing factors include multiparity, complicated delivery, ...
A persistent right umbilical vein (PRUV) is an uncommon vascular anomaly which is often detected in utero.
The estimated prevalence is at ~2 per 1000 births 1-2.
In the normal situation, the right umbilical vein begins to obliterate in the ~4th week of gestation and di...
Placenta accreta (PA) is both the general term applied to the abnormal placental adherence and also the condition seen at the milder end of the spectrum of abnormal placental adherence. This article focuses on the second, more specific definition.
In a placenta accreta, the placental villi exte...
Placenta fenestrata is one of the variations in placental morphology, which is characterised by one or more areas of focal placental atrophy lacking villi and covered only by the chorion membrane.
Placenta increta is an intermediate level in the spectrum of abnormal placental villous implantation and accounts for ~20% of such cases. The placental villi extend beyond the confines of the endometrium and invades the myometrium.
The estimated incidence is increasing (presumabl...
Placenta membranacea, also known as a placenta diffusa, is an extremely uncommon variation in placental morphology in which placenta develops as a thin membranous structure occupying the entire periphery of the chorion.
The estimated incidence is at ~1:20000-40000 pregnancies 1.
Placenta percreta is a term given to the most severe but least common form of the spectrum of abnormal placental villous adherence, where there is a transmural extension of placental tissue across the myometrium with serosal breach. It carries severe maternal as well as fetal risks.
Placenta praevia is a term given to an abnormally low position of the placenta such that it lies close to, or covers the internal cervical os.
It is a potentially life-threatening condition to both mother and infant, which may result in exsanguination. As such, antenatal diagnosis is essential...
Placental abruption refers to a premature separation of the normally implanted placenta after the 20th week of gestation and before the 3rd stage of labour. It is a potentially fatal complication of pregnancy and is a significant cause of third-trimester bleeding / antepartum haemorrhage.
Placental insufficiency is a term given to a situation where the placenta cannot bring enough oxygen and nutrients to the growing fetus.
Fetuses may present with intra-uterine growth restriction (IUGR) (especially asymmetrical IUGR).
It can be primarily caused...
Placental mesenchymal dysplasia (PMD) is a rare, benign condition that is characterised by enlargement of the placenta with multiple bunch of grape-like vesicles that can resemble a molar pregnancy by ultrasound and gross pathologic examination.
This is an often underdiagnosed an...
A placental septal cyst is a placental cyst typically located in a mid placenta. It forms between the cotyledons of the placenta. The cysts contain gelatinous material and are usually 5-10 mm in diameter. They may be present in 10-20% of placentas from full term uncomplicated pregnancies.
Placental site trophoblastic tumour (PSTT) is a rare and one of the least common (~ 0.2% 7) forms of gestational trophoblastic disease (GTD).
PSTT typically occurs in women of reproductive age with the average age around 30. It may occur after a normal pregnancy, molar pregnancy o...
Posterior urethral valves (PUVs), also referred as congenital obstructing posterior urethral membranes (COPUM), are the most common congenital obstructive lesion of the urethra and a common cause of obstructive uropathy in infancy.
Posterior urethral valves are congenital and only...
The Potter sequence is a constellation of findings demonstrated postnatally as a consequence of severe, prolonged oligohydramnios in utero.
It consists of
pulmonary hypoplasia: often severe and incompatible with life
growth restriction (IUGR)
abnormal facies (Potter fa...
Pre-term labour refers to spontaneous delivery of the fetus prior to 37 weeks of gestation. This is regardless of estimated fetal weight.
shortened cervical length
presence of cervical funneling
dilatation or internal cervical os: cons...
Pregnancy-associated plasma protein-A (PAPP-A) is a protein found in the maternal circulation and is produced by the placenta. The PAPP-A gene has been assigned to human chromosome 9q33.1 and contains 22 exons 5. PAPP-A values tend to rise exponentially during pregnancy and the reference range d...
Pre-placental abruption or haemorrhage can be subamniotic or subchorionic in location.
most often painless
Symptoms may be similar to placental abruption in other locations; however, it may not have as poor a prognosis as other placental abruption.
Preterm premature rupture of membranes (PPROM) refers to rupture of membranes prior to 37 weeks of gestation.
It is thought to occur in 0.4-2% of all pregnancies. It however may account for up to one-third of all preterm births (particularly in the United States 5).
Pulmonary hypoplasia (PH) refers to deficient or incomplete development of parts of the lung. It can develop as a result of a number of other in-utero anomalies.
The true prevalence is not well known (1.4% of all births according to Knox et.al 13), but in cases of premature ruptur...
Pulmonary sequestration, also called accessory lung, refers to the aberrant formation of segmental lung tissue that has no connection with the bronchial tree or pulmonary arteries. It is a bronchopulmonary foregut malformation (BPFM).
There are two types:
intralobar sequestration (ILS)
Retained products of conception refer to the persistence of placental and/or fetal tissue in the uterus following delivery, termination of pregnancy or a miscarriage.
Retained products of conception complicate ~1% of all pregnancies. It occurs with greater frequency with:
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...
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.
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...
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%).
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...
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...
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.