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 a serosal breach. It carries severe maternal as well as fetal risks.
Placenta previa refers to an abnormally low lying placenta such that it lies close to, or covers the internal cervical os. It is a common cause of antepartum hemorrhage.
Placenta previa is a potentially life-threatening condition for both mother and infant. As such, an antenatal diagnosis is es...
Placentomegaly is a term applied to an abnormally enlarged placenta.
It can be associated with a number of maternal and fetal disorders which include:
chronic intrauterine infections
Platyspondyly is a radiographic feature and refers to flattened vertebral bodies throughout the axial skeleton.
Platyspondyly can be feature of many conditions which include:
severe Gaucher disease 1
Polydactyly (less commonly called hyperdactyly) refers to the situation where there are more than the usual number of digits (five) in a hand or foot. It can be broadly classified as:
pre-axial polydactyly: extra digit(s) towards the thumb/hallux (radially)
post-axial polydactyly: extra digit(...
Polyhydramnios refers to a situation where the amniotic fluid volume is more than expected for gestational age.
It is generally defined as:
amniotic fluid index (AFI) >25 cm
largest fluid pocket depth (maximal vertical pocket (MVP)) greater than 8 cm 6: although some centers, particularly in ...
Polysyndactyly refers to the combined presence of polydactyly as well as syndactyly involving either the hands or feet.
Polysyndactyly can be associated with a number of syndromes which includes:
type I: Noack syndrome
type II: Carpenter syndrome (typically...
The portal sinus is an L-shaped venous confluence in the fetal circulation. It is located in the liver, between the left and right intrahepatic portal veins. The umbilical vein drains into the portal sinus at its medial aspect, near the left inferior intrahepatic portal vein 1,2. The ductus veno...
Post-axial polydactyly refers to polydactyly where the additional digit is on the ulnar margin of the hand, or lateral to the 5th toe.
Post-axial polydactyly is more common than pre-axial polydactyly, with an estimated incidence of 1 in 3000 5.
The majority of cases ar...
Post dates fetus is when there is prolonged gestation when the fetus remains in-utero beyond 2 weeks beyond expected date of delivery (>42 weeks gestation).
The reported frequency is at approximately 3-12% of pregnancies.
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...
Postpartum angiopathy is a subset of reversible cerebral vasoconstriction syndrome (RCVS), although is has been described as a separate condition. It is also known as postpartum angiitis and puerperal vasospasm. Please refer to the main article on reversible cerebral vasoconstriction syndrome (R...
Postpartum hemorrhage (PPH) refers to uterine bleeding after delivery and remains one of the major worldwide causes of maternal mortality.
A postpartum hemorrhage can be board classified as primary or secondary.
Primary postpartum hemorrhage
This is the most common ...
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 f...
Pre-eclampsia is a disorder of pregnancy involving new-onset hypertension (systolic BP ≥140 mmHg or diastolic BP ≥90 mmHg) and involvement of one or more other organ systems.
Pre-eclampsia affects up to 8% of pregnancies 1.
diabetes mellitus 2
chronic hypertension ...
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...
Pregnancy of uncertain viability (PUV) is a term given to an intrauterine pregnancy in a situation where there are not enough criteria (usually on ultrasound grounds) to confidently categorize an intrauterine pregnancy as either viable or a failed pregnancy.
The term pregnancy of unknown location is assigned when neither an intrauterine pregnancy (IUP) or an ectopic pregnancy is identified on transvaginal ultrasound in the context of a positive pregnancy test.
pelvic pain, vaginal bleeding
positive pregnancy test
Pregnancy-related osteonecrosis, also known as pregnancy-related avascular necrosis, is a common cause of femoral head osteonecrosis. Since the femoral head is deficient in blood supply, it is particularly vulnerable to osteonecrosis.
The pathophysiology is thought to be due to venou...
Pregnancy with intrauterine contraceptive device (IUCD) is uncommon and IUCD is a highly effective contraception method. Chances of pregnancy to occur is highest during the 1st year of IUCD usage and there are chances of adverse outcomes during pregnancy.
Pregnancy with IUCD may o...
Premature rupture of membranes (PROM) refers to a rupture of the amniotic sac and chorion (membranes) occurring prior to the onset of uterine contractions. When this occurs prior to 37 weeks it is then termed a pre term premature rupture of membranes (PPROM). By this definition, PROM is classifi...
Preplacental abruption or hemorrhage 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 forms of placental abruptio...
Pre-term labor 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: consi...
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).
A primary fetal hydrothorax (PFHT) is a rare situation and refers to a primary accumulation of fetal pleural fluid without any underlying abnormality. It can present with a wide spectrum of severity and can be uni or bilateral.
The estimated prevalence is at ~ 1:10,000-15,000 preg...
Proboscis is a rare congenital anomaly where an anterior appendage-like structure is seen projecting from the midline fetal face/forehead. Depending on the exact location, this has further been classified into various subtypes (e.g. interorbital proboscis).
Prolonged rupture of membranes refers to a rupture of membranes lasting longer than 18-24 hours (i.e. between time of rupture and time of delivery) 1-2. This situation can occur in either the term or pre-term newborns where in the latter case it is also termed prolonged preterm rupture of membra...
A pseudodysraphism refers to the splayed appearance of a normal spine created due to excessive craniocaudal angulation during sonographic evaluation. This can erroneously lead to the diagnosis of a spinal neural tube defect.
A pseudogestational sac, also known as a pseudosac or intra-cavitary fluid, is the concept that a small amount of intrauterine fluid in the setting of a positive pregnancy test and abdominal pain could be erroneously interpreted as a true gestational sac in ectopic pregnancy.
The sign was origi...
Pseudo-omphalocele is a spurious sonographic appearance giving an impression of an anterior abdominal wall defect.
Pseudo-omphalocele may be seen in:
scanning errors where there is a deformation of the fetal abdomen by transducer pressure and the im...
Pseudo-TORCH syndrome is a term used to denote cases that clinically resemble congenital infection (see congenital TORCH infections) but where no organisms or serological, microbiological or immunological evidence of infection can be identified 1. It is now believed that pseudo-TORCH syndrome is...
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 ruptu...
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)
Pygopagus twins are conjoined twins that are joined in the dorsal aspect, facing away from each other.
They share the sacrococcygeal and perineal regions. Fusion of sacrum and coccyx frequently occurs. The dura and the spinal cords may be fused in as many as 1/3rd of the cases.The anus, rectum,...
Rachipagus twins are an extremely rare type of conjoined twins. They are joined in the dorsal aspect and face away from each other.
Fusion of the occiput with varying segments of the vertebral column may occur, resulting in the sharing of the spinal cords. The fusion terminates above the sacrum...
Rachischisis totalis, also known as complete spina bifida, refers to a severe form of spina bifida where there is a cleft through the entire spine.
There is often a severe or complete defect of the neural tube involving the entire spine from the cervical region through to the sacrum....
Radial ray anomalies comprise of a large spectrum of upper limb anomalies which range from partial (radial hypoplasia) to a complete (radial aplasia) deficiency of the radius with or without accompanying deficiency of the thumb bones.
They can be associated with a numbe...
Redating a pregnancy may occur when there is a discrepancy between the estimated due date (EDD) calculated by last menstrual period (LMP) and that by ultrasound. Care should be taken when redating a pregnancy, especially in the third trimester, as there may be other reasons for a fetus to be sma...
Renal agenesis refers to a congenital absence of one or both kidneys. If bilateral (traditionally known as the classic Potter syndrome) the condition is fatal, whereas if unilateral, patients can have a normal life expectancy.
Unilateral renal agenesis affects approximately 1 in ...
Renal dysgenesis is a very broad term which can include any form underdevelopment of the kidneys. The spectrum includes:
renal agenesis: complete lack of formation
renal hypoplasia: partial lack of formation
Some authors also classify any form of renal maldevelopment affecting size, shape of ...
Retained products of conception (RPOC) refer to the persistence of placental and/or fetal tissue in the uterus following delivery, termination of pregnancy or a miscarriage.
RPOC complicate ~1-5% of all routine vaginal deliveries 12.
According to one prospective study, RPOC was ...
Retroplacental complex (RPC) is the region behind the placenta and is composed of decidua basalis and portions of myometrium including the maternal veins which drain the placenta.
visualized post 20 weeks of gestation
seen as an echo-poor, subplacental region...
Retroplacental hemorrhage occurs when there is perigestational hemorrhage that is confined to the retroplacental space.
This type of hemorrhage occurs behind the placenta. The hematoma, therefore, separates the placenta from the uterine wall. The source of bleeding is probably from s...
Reversal of umbilical artery end-diastolic flow (REDF) or velocity is often an ominous finding if detected after 16 weeks. It is classified as Class III in severity in abnormal umbilical arterial Dopplers 6.
The estimated incidence is at ~0.5% of all pregnancies with a much higher...
Rhizomelic dwarfism is a type of dwarfism where the dominant feature is proximal (i.e. femoral, humeral) limb shortening.
The following conditions fall under the heading of rhizomelic dwarfism 3
rhizomelic chondrodysplasia punctata
The rhombencephalon (plural: rhombencephalons or rhombencephala), or hindbrain is a primary vesicle of the neural tube.
During the fifth week of embryological development, the rhombencephalon further subdivides into the secondary brain vesicles, the metencephalon and the myelenceph...
The right ventricular outflow tract (RVOT) refers to the region of blood outlfow from the right ventricle between the supraventricular crest and the pulmonary valve. It is comprised of the conus arteriosus (infundibulum), ventricular septum and right ventricular free wall. It is commonly assesse...
The right ventricular outflow tract (RVOT) view (or three vessel view/3VV) is one of the standard views in a fetal echocardiogram. It principally assesses the right ventricular outflow tract. It is a long axis view of the heart, highlighting the path from the right ventricle into the pulmonary t...
Roberts sign refers to the presence of a gas shadow within the heart or the greater vessels, in cases of fetal death in utero. It is a rare sign caused by postmortem blood degeneration, usually seen 1-2 days after death; and may be seen as early as 12 hours.
History and etymology
Roberts syndrome, also known as Roberts-SC phocomelia syndrome, pseudothalidomide syndrome, or Appelt-Gerken-Lenz syndrome, is a rare congenital malformation syndrome.
intrauterine growth restriction
postnatal growth retardation
failure to thrive
Robinow syndrome is a rare heterogeneous genetic disorder with at least two distinct forms.
The syndrome can affect several systems, including:
mesomelic limb shortening: mesomelia
characteristic facies anomalies
A rocker bottom foot (also known as a congenital vertical talus) is a congenital anomaly of the foot. It is characterized by a prominent calcaneus/heel and a convexly rounded sole.
It results from a dorsal and lateral dislocation of the talonavicular joint.
Rothmund-Thomson syndrome (RTS) is an extremely rare autosomal recessive disorder with heterogeneous clinical features.
It is characterized by many features which include:
poikiloderma: characteristic rash, typically develops in infancy
sparse hair, eyelashes, and/or ey...
Rubinstein-Taybi syndrome (RTS) is a very rare genetic multi-system disorder primarily characterized by intellectual disability, broad and often angulated thumbs and halluces, and distinctive facial features.
The estimated incidence is 1 in 100,000-125,000 live births 5.
Ruptured omphalocele occurs when there is rupture of the outer membrane of an omphalocele. When this happens the eviscerated fetal bowel looks free floating and distinction from gastroschisis becomes difficult. However, with a ruptured omphalocele, the abdominal defect generally tends to be larg...
A rupture of membranes (ROM) or amniorrhexis is a term used during pregnancy to describe a rupture of the amniotic sac. This can occur as part of normal birth (or "spontaneously") if it occurs at full term at the onset of, or during, labor. It is also colloquially known as "breaking water."
Russell-Silver dwarfism is a very rare syndrome characterized by:
intrauterine growth restriction: tends to give an asymmetrical IUGR
postnatal growth restriction
relatively large calvarium: pseudohydrocephalus
clinodactyly/clinobrachydactyly of the small finger
a typical triangular type fa...
Sacrococcygeal teratoma (SCT) refers to a teratoma arising in the sacrococcygeal region. The coccyx is almost always involved 6.
It is the commonest congenital tumor in the fetus 11 and neonate 3. The incidence is estimated at ~1:35000-40000. There is recognized female predilectio...
SADDAN syndrome is an acronym for severe achondroplasia with developmental delay and acanthosis nigricans. It is an extremely rare condition, and as the name states, comprises a combination of skeletal, brain and cutaneous anomalies.
The syndrome results from a mutation in ...
The Sakati-Nyhan syndrome, also known as Sakati-Nyhan-Tisdale syndrome or acrocephalosyndactly type III, is an extremely rare type of acrocephalopolysyndactyly.
Its main features include:
congenital limb abnormalities
congenital heart defects
History and etymology
A sandal gap deformity, also known as hallux varus, is an imaging observation in antenatal ultrasound (typically second trimester) where there is an expanded first interspace, i.e. the gap between the great toe of the foot from the rest of the toes (likened to the gap caused by a sandal).
Scar endometriosis is a term given to endometriosis occurring in a Cesarian section scar. It can be located in the skin, subcutaneous tissue, rectus muscle/sheath, intraperitoneally, or in the uterine myometrium (within uterine scar).
The reported incidence of abdominal scar endom...
Schizencephaly is a rare cortical malformation that manifests as a grey matter lined cleft extending from the ependyma to the pia mater.
Some authors do not use the term schizencephaly, preferring to group these disorders under the blanket term of porencephaly. For the purpose of t...
Seckel syndrome is an autosomal recessive congenital dwarfing disorder.
The estimated incidence is ~1:10,000. There is no recognized gender predilection.
It is clinically characterized by many features including:
intrauterine growth restriction
The second trimester scan is a routine ultrasound examination in many countries that is primarily used to assess fetal anatomy and detect the presence of any fetal anomalies.
The second trimester extends from 13 weeks and 0 days to 27 weeks and 6 days of gestation although the majority of thes...
Semilobar holoprosencephaly is a subtype of holoprosencephaly characterized by incomplete forebrain division. It is intermediate in severity, being worse than lobar holoprosencephaly and better than alobar holoprosencephaly.
Please refer to the general article of holoprosencephaly...
Shorted fetal femur is a morphological descriptor and is usually defined when the femoral length falls below the 5th centile for gestational age (some define it when it is under the 2.5th centile 5) or less than 0.91 predicted by the bi-parietal diameter. It can occur in isolated or in associati...
Shortened fetal humerus is a morphological description and is usually defined when the humeral length falls below the 5th percentile or less than 0.9 as predicted by the biparietal diameter (BPD). It can occur in isolation or in association with a number of other anomalies.
The humeral length i...
Shortened fetal long bones (SFLB) can involve either the upper limb and/or the lower limb. It is a broad descriptive entity which can include
short fetal femur
short fetal humerus
short fetal tibia-fibula
short fetal radius - ulna
the presence of shorted fetal long ...
Shortening of the uterine cervical canal as the name implies refers to an abnormal shortening of the uterine cervical length. It is considered a sign of cervical incompetence during pregnancy and can lead to premature delivery.
primary (i.e. congenital/idiopathic)
A short maxillary length can result from many congenital and acquired causes. If seen in an antenatal ultrasound scan, it is often considered to have a high association with trisomy 21 1.
Many conditions that can cause midfacial hypoplasia will result in a short maxillar...
Short rib polydactyly syndrome(s) (SRPS) comprise a rare group of severe osteochondrodysplasias. There are four major recognized types present:
type I: Saldino-Noonan type
type II:: Majewski type
type III: Verma-Naumoff type
type IV: Beemer-Langer type
There may also be other very rare type...
SHORT syndrome refers to an acronym which primarily comprises of the following features:
S: short stature
H: hyperextensibility of joints and/or inguinal hernia
O: ocular depression
R: Rieger anomaly
T: teething delay
In a addition to these there can be numerous associated minor features w...
Short umbilical cord has been variably defined. Considering the mean length of the umbilical cord is 50-70 cm 1-2, a short cord in absolute terms is usually taken as one that is under 35-40 cm in length at term 1-2.
Recognized associations include
Simple hydropic degeneration of the placenta is a form of hydropic degeneration of the placenta that can occur in a first trimester pregnancy loss. In this situation, the serum beta HCG will tend to be low and tend to show a decline with repeat testing.
The overall sonographic appearance can va...
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 unknown reasons, the absence of the left umbilical artery is much more common (~70%).
Sirenomelia (also known as the mermaid syndrome) is a rare congenital malformation characterized by the fusion of lower limb structures.
The estimated incidence is at ~1 in 60,000-70,000 of pregnancies 9. There may be greater male predilection (somewhat paradoxical given the usage...
Skeletal dysplasia (also known as osteochondrodysplasia) refers to any abnormality in bone formation. There is a very wide clinicopathological spectrum and any part of the skeleton can be affected.
The overall prevalence is estimated at ~2 per 10,000 live births 3.
A small for dates fetus can result from a number of factors
structural anomalies (syndromes)
fetal Warfarin syndrome
hydantoin embryopathy (Dilantin TM)
A small gestational sac in early first trimester is considered a poor prognostic factor. Some authors use the mean sac diameter to crown rump length difference of 5 mm or greater to be normal 1.
The smaller than expected sac diameter in pregnancies 36-42 days from the last menstrual period ha...
A small placenta if observed on antenatal ultrasound can arise from a number of situations. They include:
variation in placental morphology: where only part of the placenta is seen
bilobed placenta: with only one lobe seen
succenturiate lobe: with either main lobe or succenturiate lobe not se...
A small yolk sac is considered a non-specific feature and, at the time of writing, there are not many publications about the clinical importance of small yolk sacs.
According to some publications, a very small yolk sac may be a normal finding during early periods of normal embryologic developme...
Smith-Lemli-Opitz syndrome (SLOS) also known as 7-dehydrocholesterol reductase deficiency is an inborn error of cholesterol synthesis.
The estimated incidence is at 1:20000-40000 live births. Prevalence may be greater in Nordic countries.
There are many wh...
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...
Snowstorm sign in obstetric imaging is classically seen in complete hydatiform mole. It is characterized by the presence of many hydropic villi which gives the ultrasonographic appearance of a central heterogeneous mass having a solid, hyperechoic area and interspersed with a multitude of cystic...
Snowstorm sign may refer to:
snowstorm sign: complete hydatiform mole (ultrasound)
snowstorm sign: extracapsular breast implant rupture (ultrasound)
snowstorm sign: thyroid pulmonary metastases (chest radiograph)
Obstetric and gynecological ultrasound is rampant with numerous cut off values. Some of these get revised over the years. The following list is a useful aid to refer to and revise.
rate of increase of a mean sac diameter per day in early pregnancy
generally accepted value for a thi...
The Spalding sign refers to the overlapping of the fetal skull bones caused by collapse of the fetal brain. It appears usually a week or more after fetal death in utero.
This finding was originally described by Alfred Baker Spalding (1874-1942), an American obstetrician 2, on abdominal radiogr...
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.
the commonest type of placental invasion (~75% of cases)
occurs in ~1 in 7...
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.
Spina bifida in its strictest sense means defective fusion of the vertebral posterior elements, leading...
Spinal dysraphisms refer to a broad group of malformations affecting the spine and/or surrounding structures in the dorsum of the embryo. They are a form of neural tube defect.
The neural tube is formed by the lengthwise closure of the neural plate, in the dorsum of the embryo.
Spondylocostal dysostosis (SCDO) is a rare condition characterized by short-trunk dwarfism secondary to developmental anomalies of the vertebrae and ribs. Previously the condition Jarcho-Levin syndrome (also known as spondylothoracic dysostosis) was grouped together with spondylocostal dysostosi...
A spontaneous rupture of membranes (SROM) refers to a rupture of fetal membranes occurring on its own (in contrast to artificial rupture of membranes). When this occurs prior to ~ 37 weeks in gestation, it is then termed spontaneous premature rupture of membranes (SPROM) which is the usual cause...