Items tagged “obstetric”

23 results found

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 nonspecific 'soft markers' for abnormal fetal development. It is considered more closely associated with trisomy 18 (Edward syndrome). ...

Intradecidual sac sign

Intradecidual sac sign (IDSS) is a useful feature in identifying an early intrauterine pregnancy 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 this ...

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...

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 ...

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 ...

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 ...

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...


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


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.

Vasa previa

Vasa previa is a term given when there are abnormal fetal vessels within the amniotic membranes that either cross or run in extreme close proximity to the internal cervical os. Pathology Vasa previa can be of two types type I (present in ~ 90% of cases with vasa previa 3): abnormal fetal vess...

Placenta percreta

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 serosal breach. It carries severe maternal as well as fetal risks. Epidemiolog...

Placenta increta

Placenta increta is an intermediate level in the spectrum of abnormal placental villous implantation and accounts for ~20% of such cases. The placental villi extend beyond the confines of the endometrium and invades the myometrium.  Epidemiology The estimated incidence is increasing (presumabl...

Placenta accreta

Placenta accreta (PA) is both the general term applied to the 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 exte...

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...

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 prevalance is estimated to be at around 1-7% 3. Pathology There is inw...

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% in twin pregnancies respectively. It is also more common in placenta previa than in normally located placentas. The prevalence...

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...

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...

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