ULTRASOUND


Gestational Age Anatomical landmarks 4 weeks 2 days


Comments


Eccentrically placed gestational sac with Mean Gestational Sac Diameter (MGSD) 2-3mm


5th week


MGSD 5mm Yolk sac (YS) Size varies from 3-8mm (average 5mm)


6th week 7th week 8th week


MGSD 10mm Embryo 2-3mm Cardiac activity (remove CA)


MGSD 20mm Head and trunk distinguishable


MGSD 25mm Head size = YS Limb buds Midgut herniation Rhombencephalon


9th week 10th week


11th week Choroid plexus, spine, limbs


Cardiac chambers, stomach, bladder, skeletal ossification


Gut returning Most structures identified


 Figure 2: Ultrasound features of early pregnancy


Diagnostic term Ultrasound criteria Empty sac


Embryonic or fetal loss


Early pregnancy loss (or delayed miscarriage)


, McParland (2010).


May represent pseudo-sac 10-20% of ectopic pregnancies have an intrauterine pseudo gestational sac (GS)


Confirms Intrauterine Pregnancy (IUP) Confirms viability (97% of embryos with cardiac activity have a normal outcome)


Poor prognosis if MGSD >20mm and no yolk sac or embryo


Gestation sac with a mean sac diameter of greater than 20mm with no visible embryo.


Embryo with greatest length of more than 6mm with no visible cardiac activity or initial visualisation of an embryo or fetus with visible cardiac activity, followed by repeat TVS showing an absence of cardiac activity.


Initial visualisation of an embryo or fetus with visible cardiac activity, followed by repeat TVS showing an absence of cardiac activity. Or


The presence of an embryo of less than 6mm in which cardiac activity is not visible when repeat scan is performed after at least seven days (may also be referred to as embryonic loss) or the presence of an intrauterine gestational sac of less than 20mm in which an embryo does not become visible when repeat scan is performed after at least seven days (may also be referred to as an empty sac)


Complete miscarriage


The ultrasound finding of an empty uterus after initial visualisation of an intrauterine gestational sac (with or without an embryo). Or


The ultrasound finding of an empty uterus in association with a positive pregnancy test, followed by rapid decrease in serum hCG levels (more appropriately termed failed pregnancy of unknown location as a failed ectopic pregnancy cannot be ruled out).


Incomplete miscarriage


Irregular heterogeneous echoes within the endometrial cavity.


 Figure 3: Transvaginal ultrasound criteria to make a diagnosis of miscarriage, Bottomley and Bourne (2009).


JUNE 2017 21


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