Items tagged “obstetric”

23 results found

Anembryonic pregnancy

Anembryonic pregnancy is a form of a failed early pregnancy, where a gestational sac develops, but the embryo does not form. The term blighted ovum is synonymous with this but is falling out of favour and is best avoided.  Clinical presentation The patient may be asymptomatic, presenting for a...

Early pregnancy

Early pregnancy roughly spans the first ten weeks of the first trimester. Radiographic features Antenatal ultrasound  0-4.3 weeks: no ultrasound findings 4.3-5.0 weeks:  possible small gestational sac possible double decidual sac sign (DDSS) possible intradecidual sac sign (IDSS) 5.1-5.5...

Gestational trophoblastic disease

Gestational trophoblastic disease (GTD) results from the abnormal proliferation of trophoblastic tissue and encompasses a wide spectrum of diseases, including: hydatidiform mole complete mole partial mole coexistent molar pregnancy invasive mole ~10% choriocarcinoma (gestational choriocarc...

Mean sac diameter

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 pregnancy Role of ...

Strawberry skull

Strawberry skull refers to the shape of the head on an antenatal ultrasound. Epidemiology Associations In general, strawberry skull is considered one of the non-specific 'soft markers' for abnormal fetal development. It is considered more closely associated with trisomy 18 (Edward syndrome). ...

Uteroplacental blood flow assessment

Uteroplacental blood flow assessment is an important part of fetal well-being assessment and evaluates Doppler flow in the uterine arteries and rarely the ovarian arteries. Pathology In a non-gravid state and at the very start of pregnancy the flow in the uterine artery is of high pulsatility ...


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 centres, particularly in ...


Oligohydramnios refers to a situation where the amniotic fluid volume is less than expected for gestational age. Often these fetuses have <500 mL of amniotic fluid. Epidemiology The estimated prevalence can be up to ~6% of pregnancies 4. Pathology Causes The causes of oligohydramnios are pr...

Intradecidual sac sign

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...

First trimester

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 ...

Double bleb sign

A double bleb sign is a sonographic feature where there is visualisation of a gestational sac containing a yolk sac and amniotic sac giving an appearence of two small bubbles 2. The embryonic disc is located between the two bubbles. It is an important feature of an intrauterine pregnancy and thu...


Anencephaly is the most severe form of cranial neural tube defect (NTD) and is characterised by an absence of cortical tissue (although the brainstem and cerebellum may be variably present) as well as an absence of the cranial vault. The morphological spectrum within anencephaly ranges from holo...


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.

Circumvallate placenta

Circumvallate placenta refers to a variation in placental morphology in which, as a result of a small chorionic plate, the amnion and chorion fetal membranes ‘double back’ around the edge of the placenta. Epidemiology The prevalence is estimated to be around 1-7% 3. Pathology There is an inw...

Placenta praevia

Placenta praevia 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 haemorrhage. Placenta praevia is potentially life-threatening condition for both mother and infant. As such, antenatal diagnosis is esse...

Vasa praevia

Vasa praevia refers to a situation where there are aberrant fetal vessels crossing over or in close proximity to the internal cervical os, ahead of the fetal presenting part. These vessels are within the amniotic membranes, without the support of the placenta. Vasa praevia is a rare but potentia...

Succenturiate lobe

A succenturiate lobe is a variation in placental morphology and refers to a smaller accessory placental lobe that is separate to the main disc of the placenta. There can be more than one succenturiate lobe. Epidemiology The estimated incidence is ~2 per 1000 pregnancies. Radiographic features...

Placenta accreta

Placenta accreta is both the general term applied to abnormal placental adherence and also the condition seen at the milder end of the spectrum of abnormal placental adherence. This article focuses on the second, more specific definition. In a placenta accreta, the placental villi extend beyond...

Velamentous cord insertion

Velamentous cord insertion is one of the types of abnormal umbilical cord insertion into the placenta. Epidemiology The estimated incidence is ~1% in singleton and 9-15% in twin pregnancies, respectively 11. It is also more common in placenta previa than in normally located placentas. The prev...

Marginal cord insertion

Marginal cord insertion is a type of abnormal cord insertion. Epidemiology The estimated incidence is at ~7% 1 of singleton pregnancies but ~25% of twin pregnancies. Hence, it is very important to locate the umbilical cord in all patients, particularly in high-risk pregnancy. Pathology In th...

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