Embryonic growth discordance

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Embryonic growth discordance is a term given to a twin growth discordance occurring during the early embryonic period. It is principally manifested by a discrepancy in crown rump length. It is considered independent of the chorionicity of the twins .

Epidemiology

Embryonic growth discordance can be a relatively common finding in early twin pregnancies with the mean discrepancy according to one study at around 3-4%.

Pathology

Associations

Many associations have been described which include:

major growth delay of one twin: later in the course of the pregnancy
aneuploidy
loss of one fetus

Practical points

for milder degrees of discrepancy, some authors suggest the CRL of the smaller fetus being a more accurate estimate of the actual gestational age
in the absence of aneuploidy or structural fetal abnormality, a recent study has suggested CRL discordance having a poor predictive value for adverse perinatal outcome in both monochorionic and dichorionic twin pregnancies; the CRL discordance is not recommended to identify twin pregnancies at high risk of adverse perinatal outcome