The fetal middle cerebral artery (MCA) pulsatility index (PI) is a key parameter used in fetal middle cerebral arterial Doppler assessment. It is calculated by subtracting the end diastolic velocity (EDV) from the peak systolic velocity (PSV) and then dividing by the time averaged (mean) velocit...
Fetal neuroblastoma is a type of congenital neuroblastoma (neuroblastoma arising in utero).
The estimated incidence is at ~1 in 20,000 births.
In the vast majority (~90%) of cases fetal neuroblastomas arise in the adrenal glands. They have been diagnosed as early as 19...
Fetal nuchal oedema is a term describing a swollen fetal cervical region. It can be thought of as a less severe form of a cystic hygroma.
It can arise from diverse causes including:
congenital cardiovascular anomalies
fetal pulmonary defects
A fetal orbital mass is a rare occurrence but can arise from many patholologies
The list includes
Tumourous orbital masses
fetal orbital teratoma
Non tumourous orbital masses
orbital encephalocoele 2
orbital heterotopic brain tissue 1
congenital cystic eyeball 4
Fetal ovarian cysts refer to an ovarian cyst detected antenatally in a female fetus. They are relatively uncommon and are usually diagnosed in the 3rd trimester 5.
From autopsy studies they are found in up to 30% of fetuses 1.
The exact aetiology is not well known at t...
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 effusions (FPE) occur when there is an accumulation of pericardial fluid in utero. In order to be considered as abnormal, is it generally accepted that the pericardial fluid thickness should be greater than 2 mm.
The estimated incidence is at ~ 2% of pregnancies ...
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...
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...
The fetal pole is the first direct imaging manifestation of the fetus and is seen as a thickening on the margin of the yolk sac during early pregnancy. It is often used synonymously with the term "embryo".
The fetal pole is usually identified at ~6.5 weeks with transabdominal ultrasound imaging...
Fetal polycythaemia is manifested by an abnormally increased central venous haematocrit (Hct) level in utero. One of the key concerns with polycythaemia is related to hyperviscosity and its associated complications.
twin to twin transfusion syndrome: in recipient twin
Fetal premature atrial contractions (FPAC's) are a type of extrasystoles that can be occasionally detected in fetal heart monitoring. They along with fetal premature ventricular contractions (PVC's) account for the majority of in utero rhythm disturbances 3.
They may arise from...
Fetal premature ventricular contractions (FPVC) are a type ectopic ventricular contractions detected in utero. They are a type of extrasystoles.
Premature ventricular contractions are often followed by a compensatory pause due to the refractory state of the conduction system; the next conducted...
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
Fetal right ventricular (RV) enlargement is an infrequently encountered situation in antenatal imaging.
The right ventricle is a dominant ventricle in in utero life. RV enlargement can occur with a number cardiac as well as non cardiac anomalies
hypoplastic left heart syndr...
Fetal rubella syndrome (FRS) is a spectrum of congenital abnormalities that results from primary maternal infection with the rubella virus. It falls under the TORCH group of infections.
It is important to note that reinfection/reactivation has significantly lower risk of fetal anomalies than co...
Fetal schizencephaly refers to schizencephaly diagnosed in utero. Usually only open lips types can be diagnosed antenatally.
may show a unilateral or bilateral defect extending from the pial surface to the ventricular wall
there may be other feature...
A fetal sinus bradycardia is a sub type of fetal bradycardia where the fetal heart rate is abnormally slow ( less than 100 beat per minute) but runs at the regular rate with sinus rhythm.
congenital long QT syndrome 1
maternal anti Ro antibodies 2-3
Fetal splenomegaly (or simply an enlarged fetal spleen) can arise from a number of situations. It can occur with or without fetal hepatomegaly.
in utero infection
in utero parvovirus B19 infection
in utero cytomegalovirus infection 1
inborn errors of metabolism
Fetal supraventricular tachycardia (SVT) is considered the most common type of fetal tachyarrhythmia and can accounts for 60-90% of such cases.
It has a typical ventricular rate of ~230-280 beats per minute (bpm) 1 and isoften associated with an accessory AV conduction pathway....
Fetal tachyarrhythmia refers to an irregular increase in fetal heart rate.
Depending on its exact definition, the prevalance rate is thought to be around 0.5-1% of pregnancies.
Many cases tend to be discovered in the 3rd trimester.
Fetal tachycardia is an abnormal increase in the fetal heart rate. It is variably defined as a heart rate above 160-180 beats per minute (bpm) and typically ranges between 170-220 bpm (higher rates can occur with tachyarrhythmias).
The estimated prevalence is ~0.4-1% of pregnancie...
Fetal thrombocytopaenia refers to an abnormally low platelet count in the fetus. The acceptable normal range for a fetal platelet count is similar to adults and do not vary significantly with gestation age. The lower limit for cut off is therefore usually taken as:
150,000/uL for thrombocytopae...
Fetal toxoplasmosis is an in utero infection that results from transplacental transmission and subsequent infection with the organism Toxoplasma gondii. It falls in the TORCH group of infections.
Please refer on congenital cerebral toxoplasmosis for a specific discussion on this condition.
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
A fetal urachal cyst refers to a urachal cyst occuring in utero. It may or may not communicate with the vertex of the fetal bladder. It may also arise within the umbilical cord. Umbilical cord urachal cysts originate from an extra-abdominal urachal system.
fetal intra-abdominal cysts...
Fetal urinary ascites is one of the causes of fetal ascites and can arise from a number of pathologies.
in utero bladder perforation
transudation from the fetal bladder
persistent urogenital sinus
The presence of fetal ascites without...
Fetal valproate syndrome (FVS) is a potential embryopathy that can occur as a result from maternal intake of valproic acid (sodium valproate / Depakote) during pregnancy.
There is a wide clinical spectrum which includes
neural tube defects
Fetal ventriculomegaly refers to the presence of dilated cerebral ventricles in utero.
Important in itself, it is also associated with other CNS anomalies.
Using the current sonographic cut-off criteria (see radiographic features below), the estimated prevalence may be at ~0.9% o...
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...
Fetal warfarin syndrome (FWS) is a rare condition which can occur as a result of fetal exposure to maternal ingestion of warfarin during pregnancy.
The increased risk is at ~6-9 weeks gestation.
Reported clinical features include:
nasal bone hyp...
Feto-maternal rhesus (Rh) incompatibility is a situation when the maternal blood is Rh-negative blood and the fetal blood is Rh-positive (from paternal inheritance). It is a type fetomaternal blood group incompatibility and can, in turn, lead to several complications which classically includes t...
Fetus-in-fetu (FIF) is an extremely rare abnormality that occurs secondary to abnormal embryogenesis in a monochorionic diamniotic pregnancy where a non-viable fetus becomes enclosed within a normally developing fetus.
This condition is thought to have a 2:1 male predominance 2.
A fimbrial ectopic pregnancy is a sub type of tubal ectopic pregnancy. This sub type accounts for ~ 5 -11% 1,3 of all tubal ectopic pregnancies. In a fimbrial ectopic, the implantation is at the fimbria of the fallopian tube which is closest to the ovary. The chance of a tubal rupture is compara...
The Finnish type congenital nephrotic syndrome is a sub type of congenital nephrotic syndrome. A large placenta and proteinuria from birth are considered hallmarks of the disease 2. The proteinuria is often of intra-uterine onset. Although it is named the Finnish type, it can occur outside Finla...
The first trimester is defined as the first 13 weeks of pregnancy following the last normal menstrual period (some authors refer to early pregnancy as 0-10 weeks). It can be divided into a number of phases, each of which has typical clinical issues. These phases are:
conceptus phase: 3-5 weeks
A floating head appearance refers to imaging features observed typically on antenatal ultrasound with certain skeletal dysplasias such as achondrogenesis.
Against the background of a poorly-mineralized spine, a normally ossified skull is seen giving an impression of a floating head.
The foramen ovale (or ovalis) is the opening in the interatrial septum in the fetal heart that allows blood to bypass the right ventricle and non-ventilated lungs, shunted from the right atrium to the left atrium. Specifically it represents the opening between the upper and lower portions of the...
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.
The four chamber cardiac view is an important and routinely performed view in both fetal echocardiography as well as on a standard second trimester anatomy scan.
The four chamber view can only detect some of the congenital cardiac anomalies (~64% according to one study 2) ...
Fowler syndrome is a rare condition characterised by
brain stem and basal ganglion calcification
glomeruloid (proliferative) vasculopathy of cerebral vessels
fetal akinesia deformation sequence with muscular hypoplasia
Sometimes a separate condition resulting in urinary re...
Fraser syndrome is an extremely rare congenital syndromic anomaly.
The estimated incidence is at around 0.04:10,000 live-born infants and 1:10,000 stillbirths.
The syndromic spectrum can comprises of:
syndactyly: often cutaneous
Freeman Sheldon syndrome (FSS) (also known as distal arthrogryposis type IIa) is a congenital condition where multiple joint contractures are a key feature. Affected individuals are known to have a characteristic facial expression resembling that of a whistling face and hence the syndrome is als...
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):
Frontonasal dysplasia is a rare disorder involving the face and often the central nervous system:
median cleft lip
absence of the nasal tip
central nervous system
cranium bifidum occultum
agenesis of the corpus callosum
Fryns syndrome (FS) is a rare congenital disorder which can have significant phenotypic variability but is primarily characterised by cranio-facial anomalies, diarphagmatic defects and distal limb anomalies.
Incidence is estimated at 1:15,000 live births.
Cervical funneling is a sign of cervical incompetence and represents the dilatation of the internal part of the cervical canal and reduction of the cervical length.
Greater than 50% funneling before 25 weeks is associated with approximately 80% risk of preterm delivery.
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...
The gestational sac (GS) is the first sign of early pregnancy on ultrasound and can be seen with endovaginal ultrasound at approximately 3-5 weeks gestation when the mean sac diameter (MSD) would approximately measure 2-3 mm in diameter.
A true gestational sac can be distinguished from a pseudo...
Gestational trophoblastic disease (GTD) results from the abnormal proliferation of trophoblastic tissue and encompasses a wide spectrum of diseases, including:
invasive mole ~10%
choriocarcinoma (gestational choriocarcinoma) ~1%
placental site t...
Goldenhar syndrome (also known as oculo-auriculo-vertebral spectrum (OAVS), Goldenhar-Gorlin syndrome or facio-auriculo-vertebral dysplasia) is a complex congenital anomaly characterised by abnormalities of the ears, eyes and vertebrae.
The estimated incidence is at 1 in 3000-500...
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...
Goodman syndrome is a type of acrocephalopolysyndactyly (often considered type IV). It is an extremely rare genetic disorder characterized by marked malformations of the head and face, abnormalities of the hands and feet, and congenital heart disease. The syndrome is inherited as an autosomal re...
The Greig cephalopolysyndactyly syndrome (GCPS) is a rare a pleiotropic, multiple congenital anomaly syndrome.
It is primarily characterized by:
pre-axial polydactyly (most common 2) or
mixed pre- and post-axial polydactyly
true ocular hypertelorism
A habitual miscarriage is the term given when a woman has had more than 3 miscarriages and it affects approximately 1-2% of women.
Many causes are identified.
mullerian duct anomalies
acquired uterine causes
uterine adhesion bands
A haematometrium refers to a uterus filled with blood.
pyometrium: uterus filled with pus
haematometrocolpos: uterus and vagina filled with blood
hydrometrium: uterus filled with fluid
Haematometrocolpos refers to a blood-filled distended uterus and vagina usually due to an anatomical mechanical obstruction precluding the evacuation of the menstrual blood.
The estimated incidence in teenagers is at ~1 in 1000-2000 5.
imperforate hymen: in ~2...
A haematosalpinx refers to intraluminal blood within the Fallopian tube (often dilated).
tubal ectopic pregnancy: common cause 1
endometriosis: common cause 5
pelvic inflammatory disease
fallopian tube torsion
Haemolytic disease of the newborn (HDN) results when maternal antibodies attack the fetal red blood cells, leading to a haemolytic anaemia and accumulation of bilirubin in the fetus or newborn. It can affect the newborn to varying degrees of severity. When the condition occurs in utero, the term...
Haemorrhagic corpus luteal cysts result from bleeding into corpus luteal cysts.
Commonly described findings include
complex adnexal mass
adnexal thick walled cystic lesion with lace like strands
adnexal thick walled cystic lesion with low-level echoes withi...
Hanging noose sign in obstretric imaging is a rarely described but classical finding of a true umbilical cord knot. It demonstrates a transverse section of the umbilical cord surrounded by a loop of umbilical cord and changes in the pressure of the knot can be demonstrated with the fetus movemen...
Head circumference (HC) is one of the basic biometric parameters used to assess fetal size. HC together with biparietal diameter (BPD), abdominal circumference (AC), and femur length (FL) are computed to produce an estimate of fetal weight. In the second trimester this may be extrapolated to an ...
HELLP syndrome is a pregnancy-related condition and is an abbreviation for:
elevated liver enzymes and
It is considered a severe and life threatening form of pre-eclampsia although it can occur without co-existing pre-eclampsia.
The estimated inciden...
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...
Hemivertebra is a type of vertebral anomaly and results from a lack of formation of one half of a vertebral body. It can be a common cause of a congenital scoliosis.
The estimated incidence is at ~0.3 per 1000 live births 2.
It falls under the spectrum of segmentation...
Herlyn-Werner-Wunderlich (HWW) syndrome, is a rare anomaly characterised by Müllerian duct anomalies (MDA) associated with mesonephric duct anomalies 3. This entity is also known as obstructed hemivagina and ipsilateral renal anomaly (OHVIRA). It is not to be confused with the Wunderlich syndro...
Heterotopic pregnancy is a rare situation when there is an intra-uterine and extra-uterine pregnancy occurring simultaneously.
The estimated incidence in the general population is estimated at 1:30,000 (for a naturally conceived pregnancy 7). The incidence among patients with assi...
Holoprosencephaly (HPE) is a rare congenital brain malformation resulting from incomplete separation of the two hemispheres.
Classically three subtypes have been recognised, however additional entities are now included in the spectrum of the disease. The three main subtypes, in order of decreas...
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...
Hydranencephaly is a rare encephalopathy that occurs in-utero. It is characterised by destruction of the cerebral hemispheres which are transformed into a membranous sac containing cerebrospinal fluid and the remnants of cortex and white matter 1.
Porencephaly is considered a less severe degree...
Hydrolethalus syndrome is a rare lethal genetic syndrome characterised by multiple developmental defects of fetus which include
cleft lip + / - palate
agenesis of the corpus callosum
absent midline stru...
Hydropic degeneration of the placenta is a phenomenon where numerous cystic spaces are formed within the placenta which is often accompanied by placental enlargement. It can occur in a number of situations which include
simple hydropic degeneration in 1st trimester pregnancy loss - fetal demise...
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...
Hypertelorism refers to an abnormal increase in distance between any two organs although some authors use the term synonymously with orbital hypertelorism meaning an abnormal increase in distance between the two eyes. The article mainly focuses on the latter. The abnormality is similar to teleca...
There are several hypertensive states that can manifest in pregnancy. They include:
gestational hypertension - pregnancy induced hypertension (PIH)
They may be commoner in young primigravid as well as older multiparous women.
A hypocoiled umbilical cord to an umbilical cord with less than normal coiling. This is normally estimated by a low umbilical cord coiling index (usually less than 0.2 2).
single umbilical artery
abnormal cord insertion(s)
non coiled umbilical cord
Hypophosphatasia refers to a rare metabolic disorder characterised by deficient serum alkaline phosphatase activity. The effects of hypophosphatasia are primarily seen in the skeletal system. The condition has marked variation in clinical expression (see subtypes).
The true incide...
Hypoplasia of the nasal bone refers to a sonographic observation where the fetal nasal bone appears smaller by varying degrees.
There is a spectrum of nasal bone hypoplasia, at one end of which is the relatively easily identified absent nasal bone. The other end of the spectrum is considerably ...
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...
Hysterosalpingogram (HSG) is a fluoroscopic examination of the uterus and the Fallopian tubes, most commonly used in the investigation of infertility or recurrent spontaneous abortions.
Infertility to assess uterine morphology and tubal patency.
Ileal atresia is a congenital abnormality where there is significant stenosis or complete absence of a portion of the ileum. There is an increased incidence in those with chromosomal abnormalities.
This article will focus on ileal atresia alone but bear in mind that some cases correspond to jej...
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...
Increased fetal abdominal circumference is usually given when the abdominal circumference lies above the 90th percentile. During the second and especially third trimesters an increased abdominal circumference usually contributes to a high estimated fetal weight (large for dates fetus), which has...
Induced fetal demise as the name suggests, refers to an iatrogenically induced fetal demise, most often by injection of a pharmacologic agent.
selective or non selective reduction of one of the fetuses in a multifetal pregnancy
fetal demise is often induced before medical or surgi...
Inevitable miscarriage refers to the presence of an open internal os in the presence of bleeding in the first trimester of pregnancy. Most often the conception products are not expelled and intracervical contents are present at the time of examination. A sac may be seen low within the uterus and...
Iniencephaly is a rare neural tube defect resulting in the following features 1-2:
occipital bone defect
partial or total absence (rachischisis) of cervico-thoracic vertebrae
fixed fetal head retroflexion
The estimated incidence is at ~0.1-10 per 10,000 live births 5. There i...
The interocular distance (IOD) is a measurement between the two medial canthi of each eye. It is often measured as an accessory biometric parameter on routine antenatal ultrasound scans on the axial images. As a rule of thumb, the interorbital distance should be roughly equal to the ocular diame...
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...
The interstitial line sign is an ultrasound finding in interstitial ectopic pregnancy. It is an echogenic line from the mass to the endometrial echo complex. Reportedly it has high sensitivity (80%) and specificity (98%).
The inter twin membrane refers to a membraneous seperation between two fetuses in a twin pregnancy. Depending on the chorionicity and amnionicity, the membrane may have a number of layers
di-chorionic di-amniotic (DCDA) pregnancy
composed of two chorionic and two amniotic layers
usually has ...