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...
Hemorrhagic 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 obstetric 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 fetal movement...
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 of all or part of a cerebral hemisphere. This results from either increased proliferation or decreased apoptosis (or both) of developing neurons 2.
Hemimegalencephaly is a cryptoge...
Hemivertebra is a type of vertebral anomaly and results from a lack of formation of one half of a vertebral body. It is a common cause of congenital scoliosis.
The estimated incidence is at ~0.3 per 1000 live births 2.
It falls under the spectrum of segmentation anoma...
Herlyn-Werner-Wunderlich (HWW) syndrome, is a rare anomaly characterized 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 syndrom...
Heterotopic pregnancy is a rare situation when there is an intra-uterine and extra-uterine (i.e. ectopic) 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 pat...
High-risk pregnancies are any that actually or potentially threaten either the health or life of the mother or her fetus during pregnancy, labor, or birth. From a radiological perspective, high-risk pregnancies may undergo further screening or have close follow-up with growth and well-being scan...
Holoprosencephaly (HPE) is a rare congenital brain malformation resulting from incomplete separation of the two hemispheres.
Classically three subtypes have been recognized, however additional entities are now included in the spectrum of the disease. The three main subtypes, in order of decreas...
The hydatidiform moles are one of the most common but benign forms of gestational trophoblastic disease.
Hydatidiform moles are one of the common complications of gestation, estimated to occur in one of every 1,000-2,000 pregnancies 3. These moles can occur in a pregnant woman of...
Hydranencephaly is a rare encephalopathy that occurs in-utero. It is characterized 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 characterized 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 is defined as the accumulation of fluid +/- edema involving at least two fetal compone...
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 characterized 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.
Ian Donald (1910-1987) was a Scottish obstetrician who pioneered the diagnostic use of ultrasound in medicine.
Ian Donald was born in Lisgeard, Cornwall, United Kingdom on 27 December 1910 6. His father was a general practitioner. In 1925 his family moved to South Africa where he at...
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 cervicothoracic vertebrae
fixed fetal head retroflexion
The estimated incidence is at ~0.1-10 per 10,000 live births 5. There is...
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 intramural ectopic pregnancy, is an important type of ectopic pregnancy with higher risks of rupture and hemorrhage compared to usual tubal ectopic pregnancies.
The term interstitial pregnancy is sometimes interchangeably used with cor...
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 intertwin membrane refers to a membraneous separation 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 a...
Intertwin membrane folding is an observation where the intertwin membrane in a twin pregnancy appears as being folded. It is sometimes used as a predictor for the development of twin to twin transfusion syndrome. It occurs as a result of amniotic fluid discordance.
Some reports suggest that fol...
Intracranial cystic lesions in the perinatal period can carry a relatively wide differential which includes:
Supratentorial cystic lesions
choroid plexus cyst
Intracranial teratomas are uncommon intracranial neoplasms, which can have a bewildering variety of components and thus a wide range of appearances. They can be divided into two broad categories, intra- and extra-axial, which differ in epidemiology and clinical presentation. Another method of cl...
Intradecidual sac sign (IDSS) is a useful feature in identifying an early intrauterine pregnancy (IUP) as early as 25 days of gestation 1. The threshold level (earliest one can see the sign) is 24 days of gestation and the discriminatory level (one should always see the sac) is 47 days. As per t...
Intramembranous ossification describes the process of ossification from mesenchymal cells (stem cells) without a cartilaginous template and is involved in the healing process of fractures. The stages of intramembranous ossification osteogenesis are as follows:
mesenchymal cells differentiate in...
Intrauterine blood clot can result from a number of situations in gravid, non-gravid and postpartum states. It can mimic many other pathologies.
Any condition that predisposes to an intrauterine hemorrhage can potentially result in an intrauterine blood clot.
Intrauterine contraceptive devices (IUCD) (also known as intrauterine devices (IUD) and colloquially commonly as the coil) are one of the most frequently used methods of contraception throughout the world. It prevents pregnancy by:
thinning the endometrial lining
preventing sperm motility
The presence of intrauterine gas (a.k.a. pneumouterus) can sometimes be inferred by tiny internal echoes on ultrasound, foci of very low attenuation at computed tomography (CT) or signal voids with susceptibility artifact at MRI. The term encompasses air within the uterine cavity as well as intr...
Intrauterine growth restriction (IUGR) or fetal growth restriction (FGR) is defined as an estimated fetal weight (EFW) / abdominal circumference (AC) at one point in time during pregnancy being below 3rd percentile or EFW/AC below the 10th percentile for gestational age with deranged Doppler pa...
An echogenic membrane might be seen within the uterus during pregnancy:
membrane of maternal origin
membrane of fetal origin
In utero bowel perforation results in a chemical peritonitis (meconium peritonitis) from peritoneal leakage of sterile meconium.
It can result from many causes which include:
in utero intestinal ischemia
In utero Herpes simplex infection usually occurs from transplacental transmission of the Herpes simplex virus. Transplacental intrauterine infection with herpes simplex virus is an extremely rare complication of primary herpes simplex in pregnancy.
Fetal HSV infection much less co...
In utero infections, also known as congenital infections, can result from a vast number of etiological organisms and account for 2% to 3% of all congenital anomalies 4.
in utero toxoplasmosis infection / congenital toxoplasmosis infection:
congenital cerebral toxoplasmosis
In utero syphilis infection, or congenital syphilis, results from transplacental transmission of the maternal infection from the spirochete Treponema pallidum, subspecies pallidum.
For a general discussion, and for links to other system specific manifestations, please refer to the article on s...
An in utero varicella zoster virus infection is an infrequent type of in utero infection. The clinical features can be diverse and variable depending on the stage of gestation.
Fetal infection with varicella is unusual in the current age due to most women of childbearing age being...
Invasive mole is a tumorous growth associated with gestation and falls under the spectrum of gestational trophoblastic disease. Due to their aggressive growth characteristics, invasive moles are considered locally invasive non-metastasizing neoplasms.
An invasive mole develops in ...
An irregular gestational sac as the name suggests is a gestational sac which does not have the well defined, regular borders of a normal gestational sac. It is an imaging feature related to a non-viable pregnancy.
irregular yolk sac
An irregular yolk sac or an abnormally shaped yolk sac is an imaging feature that can be observed in early pregnancy scanning. It may be seen in up to 17% of early pregnancy scans 1. In contrast to an irregular gestational sac, the observation of an irregular yolk sac in not thought to correlate...
An isolated cleft palate is a type of facial cleft. This is a much rarer occurrence than a cleft lip +/- palate and is thought to represent a different pathological entity.
The estimated incidence is at ~1 per 2000-2500 pregnancies 4-5. There may be a slight female predilection 4....
Isolated inferior vermian hypoplasia (IIVH), also referred as part of Dandy-Walker variant (DWV), is a congenital malformation characterized by partial absence of the inferior portion of the cerebellar vermis.
The term Dandy-Walker variant was created to include those malformations...
An isthmic ectopic pregnancy is a subtype of tubal ectopic pregnancy an accounts for ~12% of such cases. According to one study, the rate of tubal wall disruption was higher than with an ampullary ectopic pregnancy, suggesting that in an isthmic ectopic pregnancy, the trophoblast penetrates the ...
IUCD (intrauterine contraceptive device) related uterine perforations are one of the causes of uterine perforation. It is a rare, but serious complication of an intrauterine contraceptive device, and is often clinically silent.
The incidence rate is reported at ~2 in 1000 2.
The Jarcho-Levin syndrome (JLS) or spondylothoracic dysostosis is a rare autosomal recessive heterogeneous disorder that can occur with variable severity. Previously the condition spondylocostal dysostosis was also considered as part of the JLS spectrum but is now considered a distinct pathologi...
Juberg-Hayward syndrome (JHS), also known as the oro-cranio-digital syndrome, is a rare autosomal recessive syndrome characterized by the association of the following:
cleft lip and palate
minor vertebral and rib anomalies 4
horseshoe kidneys 4
Kinking of the brainstem is a rare finding in fetal or pediatric neuroimaging, invariably seen in association with other cerebral abnormalities. It generally heralds a poor neurological outcome.
A kinked brainstem may be seen on fetal MRI, commonly after referral from ult...
This article lists a series of labeled imaging anatomy cases by system and modality.
CT head: non-contrast axial
CT head: non-contrast coronal
CT head: non-contrast sagittal
CT head: angiogram axial
CT head: angiogram coronal
CT head: angiogram sagittal
CT head: venogram axial
There are two described lambda signs:
lambda sign (twin pregnancy)
lambda sign (sarcoidosis)
A large for date uterus is a clinical observation based on uterine fundal height, which may result in referral for ultrasound assessment, usually in mid to late pregnancy.
constitutionally large fetus
Large loop excision of the transformation zone (LLETZ) is a gynecological procedure. It is currently one of the most commonly used approaches to treat high grade cervical dysplasia - cervical intraepithelial neoplasia.
A large yolk sac is one measuring >5-6 mm in pregnancies between a gestational age of 5-10 weeks. One study had shown that a yolk sac diameter of >5 mm can be associated with an increased risk of spontaneous miscarriage although few other authors have mentioned the existence of a very large yolk...
Larsen syndrome (LS) is an extremely rare disorder, often classified as a type of osteochondrodysplasia.
The estimated incidence is thought to be at ~ 1 in 100,000 people. There may be an increased female predilection.
It is characterized by many features i...
The left ventricular outflow tract (LVOT) view (or five chamber view) is one of the standard views in a fetal echocardiogram.
It is a long-axis view of the heart, highlighting the path from the left ventricle into the ascending aorta (left ventricle outflow tract).
In this view, the right vent...
The lemon sign, noted on antenatal imaging, is one of the many notable fruit-inspired signs. It is a feature when there appears to be an indentation of the frontal bone (depicting that of a lemon). It is classically seen as a sign of a Chiari II malformation and also seen in the majority (90-98%...
Lethal multiple pterygium syndrome (LMPS) is a lethal subtype of the multiple pterygium syndrome.
congenital cardiac anomalies 10
It is primarily characterized by the presence of pterygia (or wings) present in two or more bo...
Lethal omphalocele-cleft palate syndrome is, as the name suggests, characterized by the association of omphalocele and cleft palate.
Prevalence is assumed to be <1 per 1,000,000. It has been postulated that this syndrome is likely to be an autosomal recessive condition 1.
History and etymolog...
Lethal skeletal dysplasias form a heterogeneous group which are commonly characterized being non-survivable for prolonged periods ex-utero. They include:
chondrodysplasia punctata: lethal variants
metatropic dysplasia: lethal variants 4...
The limb-body wall complex (LBWC) is a rare variable group of congenital limb and body wall defects (involving mainly the chest and abdomen). They can include:
abdominoschisis: usually large and left-sided 4, and almost always present
thoracic wall defect / thoracoschisis
Lithopaedions, also referred as stone babies, are a rare phenomenon which occurs most commonly when a fetus dies during an ectopic pregnancy.
The estimated incidence is at ~ 1.5 to 1.8% of abdominal ectopic pregnancies 4.
If the deceased fetus is too large to be re-abs...
A live ectopic pregnancy is an ectopic pregnancy where a live extrauterine fetus can be demonstrated.
Loeys-Dietz syndrome is an autosomal dominant connective tissue disorder which has many features similar to Marfan syndrome.
The disease is characterized by skeletal manifestations and vasculopathies. Although Loeys-Dietz syndrome shares many similarities with Marfan syndrome, the course is oft...
A long philtrum is a clinical or imaging observation where the philtrum (middle part of the upper lip) is longer than normal.
It can be associated with a number of anomalies which include
Cornelia de Lange syndrome
A long umbilical cord has been variably defined. Considering the mean length of the umbilical cord at ~50-70 cm 1, a long cord in absolute terms is usually taken as one that is over 70 cm in length at term 1-3.
increased incidence of umbilical cord knots
increased incidence of ...
Lowe syndrome, also known as the oculocerebrorenal syndrome of Lowe, is a multisystem disorder characterized by anomalies primarily affecting the eyes, nervous system, and kidneys.
It is an extremely rare, pan-ethnic disease, with an estimated prevalence in the general population ...
Low-lying placenta occurs when the placenta extends into the lower uterine segment and its edge lies too close to the internal os of the cervix, without covering it. The term is usually applied when the placental edge is within 0.5-5.0 cm of the internal cervical os 1. Some alternatively give th...
Low set ears is a descriptive term used to given a depressed or abnormally low positioning of the pinna by two or more standard deviations below the population average.
Low set ears can be associated with a number of anomalies which include:
aneuploidic / chromosomal s...
Luteomas of pregnancy are a rare non-neoplastic condition in which luteinized stroll cells in the ovary markedly increase in size. Luteomas are hormonally active, and produce testosterone resulting in maternal and potentially fetal hirsutism and virilization.
More common in both m...
Macroglossia means an enlarged tongue. It may be absolute (greater than the 95th centile) or relative (enlarged compared with oral cavity).
Recognized associations include:
tends to be a relative macroglossia
may also have intermi...
Marginal cord insertion, also known as a 'battledore insertion', is a type of abnormal cord insertion.
Insertion of the umbilical cord within <2 cm from the placental margin is described as marginal cord insertion (usually defined as <2 cm 5 although some references define it as <1...
Marginal placental abruption is the most common type of placental abruption wherein a hematoma 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 segm...
A marginal placental previa (or grade 2 placenta previa) is a form of placenta previa where placental tissue reaches the margin of the internal cervical os, but does not cover it.
Marshall-Smith syndrome (MSS) is a rare genetic syndrome primarily comprising the triad of facial dysmorphism, failure to thrive and accelerated osseous maturation 5. Many cases, however, have a wider clinical spectrum.
failure to thrive
Maternal hydronephrosis in pregnancy often results as a physiological phenomenon due to the presence of the fetus.
It is estimated that up to 90% of women have some degree of asymptomatic dilatation of the renal calyces, the renal pelves and the upper two-thirds of the ureters du...
Maternal serum alpha fetoprotein (MSAFP) is a screening test that examines the level of alpha fetoprotein (AFP) in a pregnant woman. AFP is produced by both the yolk sac and foetal liver during pregnancy.
Ideally, all pregnant women should undergo the screening test between 15-20 w...
McKusick Kaufman syndrome (MKS) is an autosomal recessive multiple malformation syndrome primarily characterized by
hydrometrocolpos - vaginal atresia
congenital heart disease
Mean sac diameter (MSD) is a sonographic measurement of the gestational sac, which is usually first seen at around 3 weeks after conception (5 weeks after the last menstrual period), when it measures 2-3 mm.
MSD = (length + height + width)/3
Normal MSD (in mm) + 30 = days of pregn...
Meckel-Gruber syndrome (MGS) is classically characterized by the triad of:
renal cystic dysplasia: multiple renal cysts (present most cases)
occipital encephalocoele/holoprosencephaly (~70%)
postaxial polydactyly: usually hexadactyly (~65%)
Additional hepatic developmental defects and hepati...