The fetal head sparing theory is one that underpins asymmetrical intra-uterine growth restriction, where the difference between normal head circumference and decreased abdominal circumference is attributed to the fetus's ability to preferentially supply the cerebral, coronary, adrenal and spleni...
Fetal heart beat can be detected as early as 34 days (just under 6 weeks) gestation on good quality, high frequency transvaginal ultrasound, as a crown rump length (CRL) of as little as 1-2 mm.
If a fetal heartbeat cannot be identified with a CRL ≥7 mm using transvaginal scanning, then embryona...
A normal fetal heart rate (FHR) usually ranges from 120 to 160 beats per minute (bpm) in the in utero period. It is measurable sonographically from around 6 weeks and the normal range varies during gestation, increasing to around 170 bpm at 10 weeks and decreasing from then to around 130 bpm at ...
Fetal hepatomegaly (or more simply an enlarged fetal liver) can occur in number of situations. It can occur with or without fetal splenomegaly.
in utero infections
fetal parvovirus B19 infection
fetal cytomegalovirus infection 3
transient abnormal myelopoiesis (TAM) associated...
Fetal hepatosplenomegaly refers to the combined enlargement of both the fetal liver and the fetal spleen. This can occur from a number of pathologies, including:
transient abnormal myelopoiesis (TAM) 1-2 associated with trisomy 21
in association with fetal hydrops
in utero infections
The fetal hydantoin syndrome refers to a spectrum of features that can develop in a small proportion (~ 10% 5) of women taking the anti-epileptic drug phenytoin (DilantinTM) during pregnancy.
increased risk of intracranial bleeding
A fetal hydrocele refers to a hydrocele 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 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 ...
Fetal hydronephrosis represents the abnormal dilatation of the fetal renal collecting system, with pelviureteric junction obstruction the most commonly encountered cause.
Please, refer to the article on fetal pyelectasis for a dedicated discussion on this relatively common and usually benign f...
A fetal hydrothorax refers to fluid in the fetal thoracic cavity. In many cases it represents a fetal pleural effusion. In selected cases it can be treated by an in utero thoracocentesis or a formation of an in utero pleuro-amniotic shunt.
primary fetal hydrothorax
Fetal hypoxia (FH) (also known as intrauterine hypoxia (IH)) occurs when the fetus is deprived of an adequate supply of oxygen.
Fetal hypoxia can occur from a number of reasons:
umbilical cord prolapse
cord occlusion or cord thrombosis
A fetal interhemispheric cyst refers to an interhemispheric cyst diagnosed in utero. It is seen as a cystic collection located in the interhemispheric fissure, with or without communication with the ventricular system.
agenesis of the corpus callosum: strong association...
Fetal intra-abdominal cystic lesions can arise from a number of physiological and pathological causes.
fetal gastric dilatation / fetal gastric bubble (can be pathological if there is a gastric outlet obstruction
normal fetal gallbladder
No color flow
Fetal intracranial calcification refers to intracranial calcification detected in utero. This can arise from a number of pathologies which include:
in utero infections
fetal toxoplasmosis infection: calcification tends to be randomly distributed
fetal cytomegalovirus infection1: calcificatio...
Fetal intracranial cystic lesions can arise from a number of pathologies, including:
fetal arachnoid cyst
fetal choroid plexus cyst
fetal connatal cyst
fetal porencephalic cyst
fetal interhemispheric cyst
fetal subependymal cyst
dorsal cyst of holoprosencephaly
Fetal intracranial hemorrhage may occur either within the cerebral ventricles, subdural space or infratentorial fossa.
Hemorrhages can occur in a number of situations:
mechanical trauma, e.g. maternal abdominal blunt or birth trauma
severe fetal hypoxia
background fetal thrombocyt...
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 of the femur can occur as part of normal variation.
Conditions associated with fetal limb bowing include:
campomelic dysplasia 1
thanatophoric dysplasia 2: particularly type...
Fetal maceration is one of the signs of fetal death. It is a destructive aseptic process that appears between 12 to 24 hours after fetal death. It may not be seen in a pregnancy earlier than 6 months. In this a separation of the skin from head and trunk occurs giving a bubble-like appearance.
Fetal macrocephaly is a term given when the fetal head circumference lies above 2 standard deviations for the expected stage of gestation. While it can be associated with certain syndromic anomalies, in the absence of associated anomalies, it does not appear to be a significant risk factor for a...
Fetal macrosomia (also sometimes termed large for gestational age) is usually defined when the estimated fetal weight (EFW) is greater than the 90th percentile. According to this definition, it affects up to 10% of all live births. Some also use an increased birthweight (i.e. greater than 4500g)...
Fetal MCA systolic/diastolic (S/D) ratio is an important parameter in fetal middle cerebral arterial Doppler assessment. It is a useful predictor of fetal distress and intrauterine growth restriction (IUGR).
During pregnancy the middle cerebral (and other intracranial)...
Fetal megacystis refers to the presence of an unusually large bladder in a fetus.
The estimated incidence of antenatal imaging is at ~1:1500 pregnancies.
It can result from a number of causes but the main underlying mechanism is either distal stenosis or reflux.
Fetal middle cerebral arterial (MCA) Doppler assessment is an important part of assessing fetal cardiovascular distress, fetal anemia or fetal hypoxia. In the appropriate situation it is a very useful adjunct to umbilical artery Doppler assessment. It is also used in the additional work up of:
The fetal middle cerebral arterial (MCA) peak systolic velocity (PSV) is an important parameter in fetal MCA Doppler assessment.
The fetal MCA should be sampled~2 mm from the origin of the fetal internal carotid artery and the angle of the ultrasound beam and the directi...
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 edema 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 omental cyst is a type of fetal enteric cyst.
The most common type of omental cyst is considered a lymphangioma 2.
May be seen in an intra-abdominal cyst without any associated color flow. Omental cysts tend to be typically found...
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 etiology is not well known at t...
Fetal parvovirus B19 infection is a type of in utero infection. In certain cases it can lead to intrauterine fetal death.
It was first reported to be associated with fetal death and hydrops fetalis in 1984. Human parvovirus B19 is the only known parvovirus 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, it is 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 tumor occurring in a fetus.
It is a type of germ cell tumor and arises from pluripotent cells derived from all three germinal layers. In contrast to ovarian teratoma...
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 polycythemia is manifested by an abnormally increased central venous hematocrit (Hct) level in utero. One of the key concerns with polycythemia is related to hyperviscosity and its associated complications.
twin to twin transfusion syndrome: in recipient twin
Fetal premature atrial contractions 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.
Premature atrial contractions may ...
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 the dominant ventricle during in utero development. Right ventricular enlargement can occur with a number of cardiac as well as non-cardiac anomalies.
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...
Fetal sinus bradycardia is a subtype of fetal bradycardia where the fetal heart rate is abnormally slow (<100 bpm) but runs at the regular rate with sinus rhythm.
congenital long QT syndrome 1
maternal anti Ro antibodies 2-3
There are four sutures in the fetal skull vault of obstetric importance:
1. frontal suture: it lies between the two frontal bones
2. sagittal suture: it lies between the two parietal bones
3. coronal suture: it lies between the parietal and frontal bones
4. lambdoid suture: it lies between t...
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 account 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. There i...
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 thrombocytopenia 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 thrombocytopeni...
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 to congenital cerebral toxoplasmosis for a specific discussion on this condition.
Tricuspid regurgitation (TR) (also known as tricuspid insufficiency) is a common finding in imaging of the fetus. Tricuspid regurgitation represents the abnormal backflow of blood into the right atrium during right ventricular contraction due to valvular leakage (i.e. it is a valvulopathy).
Although rare, a number to tumors may be diagnosed antenatally. These fetal tumors are a diverse and a unique group of conditions, and include:
neuroblastoma: most common tumor 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 fe...
Fetal valproate syndrome (FVS) is a potential embryopathy that can occur as a result from maternal intake of valproic acid (sodium valproate) during pregnancy.
There is a wide clinical spectrum which includes
neural tube defects
A rare entity, fetal ventricular tachycardia presents with a rapid ventricular rate exceeding, and occurring independently from, the atrial rate. The ventricular rate is typically over 180 beats per minute 1. Atrioventricular dissociation is characteristic; two separate pacemakers dictate the a...
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.
Reported clinical features include:
nasal bone hypoplasia
nasal bridge depression
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 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.
Fetus-in-fetu is very rare, with an incidence of 1/500,000 live birt...
The spelling fetus is the preferred spelling in the medical world, regardless of location. It is used by virtually all biomedical journals. Therefore it is also the preferred spelling on Radiopaedia and we never use the spelling foetus. This latter spelling is still often used by lay-people in t...
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.
Folate deficiency (hypovitaminosis B9) is the most common vitamin deficiency in the Western world. It is especially important in pregnant women and common amongst alcoholics.
Deficiency arises in two distinct populations:
increased demand (pregnancy and lactation)
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 a rare anomaly of the umbilical cord, which can be detected on an 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, also known as proliferative vasculopathy and hydranencephaly-hydrocephaly syndrome (PVHH), is a rare inherited condition.
Not to be confused with Fowler syndrome of urinary retention, a condition caused by primary failure of urethral sphincter relaxation resulting ...
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 comprise 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, also known as median cleft face syndrome, is a rare disorder characterized by midline defects involving the face, head, and central nervous system.
Frontonasal dysplasia is considered to be a very rare condition, with approximately 100 cases having been repo...
Fryns syndrome (FS) is a rare congenital disorder which can have significant phenotypic variability but is primarily characterized by cranio-facial anomalies, diarphagmatic defects and distal limb anomalies.
Incidence is estimated at 1:15,000 live births.
Cervical funnelling 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% funnelling before 25 weeks is associated with ~80% risk of preterm delivery.
Gartner duct cysts develop from embryologic remnants of the Wolffian (mesonephric) duct. They are often noticed incidentally on ultrasound or MRI.
They may cause mass effect on adjacent structures.
Gartner duct cysts are located in the anterolateral ...
Gastroschisis refers to extra-abdominal herniation (evisceration) of fetal or neonatal bowel loops (and occasionally portions of the stomach and or liver) into the amniotic cavity through a para-umbilical anterior abdominal wall defect.
The estimated incidence is at around 1-6 p...
The gestational age (GA) of a fetus is most accurately determined by measuring the crown rump length (CRL) in the first trimester. The later the pregnancy, the larger the standard deviation of the estimated GA and thus EDD is. Mean sac diameter (MSD) before a fetal pole is identified and bipari...
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:
coexistent molar pregnancy
invasive mole ~10%
choriocarcinoma (gestational choriocarc...
Goldenhar syndrome, also known as oculo-auriculo-vertebral spectrum (OAVS), Goldenhar-Gorlin syndrome or facio-auriculo-vertebral dysplasia, is a complex congenital anomaly characterized by abnormalities of the ears, eyes and vertebrae.
The estimated incidence is at 1 in 3000-5000...
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 pleiotropic, multiple congenital anomaly syndrome. It is primarily characterized by:
preaxial polydactyly (most common 2) or
mixed pre- and postaxial 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
hematometrocolpos: uterus and vagina filled with blood
hydrometrium: uterus filled with fluid
Hematometrocolpos 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 hematosalpinx 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
Hemolytic disease of the newborn (HDN) results when maternal antibodies attack the fetal red blood cells, leading to a hemolytic anemia 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 is...