Embryonic growth discordance

Last revised by Arlene Campos on 7 May 2024

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 5.

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%.

Many associations have been described which include:

  • for milder degrees of discrepancy, some authors 2 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 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 4

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