Early fetal anatomy assessment at 11–14 weeks: what can realistically be examined (ISUOG 2023)
The updated ISUOG 2023 guidelines (ISUOG Practice Guidelines (updated): performance of 11–14-week ultrasound scan. Ultrasound Obstet Gynecol. 2023;61(1):127–143) regulate the performance of ultrasound examination in the first trimester, including pregnancy dating and fetal anatomy assessment. The precise list of mandatory anatomical structures to be examined in the provided fragments is not specified [to be clarified].
Pregnancy Dating
Gestational age determination is performed using crown-rump length (CRL). A systematic review of CRL charts for dating is described in the work by Napolitano R et al. (BJOG. 2014;121(5):556–565). Specific ranges and formulas are not indicated in the fragments [to be clarified].
Fetal Anatomy Assessment
Detailed assessment of fetal anatomy in the first trimester is possible at 11, 12, and 13 weeks (Luchi C et al., J Matern Fetal Neonatal Med). Routine examination at 11–13 weeks allows diagnosis of a portion of non-chromosomal fetal anomalies (Syngelaki A et al., Ultrasound Obstet Gynecol. 2019;54:468–476). The application of a standardized anatomical protocol increases screening effectiveness (Liao Y et al., Am J Obstet Gynecol. 2021;224:396).
A systematic review (Karim JN et al., Ultrasound Obstet Gynecol. 2017;50:429–441) demonstrated that the detection of structural anomalies in the first trimester depends on factors affecting screening quality. Specific sensitivity values are not provided in the fragments [to be clarified].
Specific First Trimester Findings
Among the findings described in the sources are: cystic hygroma (Scholl J, Chasen ST, Prenat Diagn. 2016), fetal edema in early pregnancy (Ramkrishna J et al., Prenat Diagn. 2021), abdominal fetal cysts (Khalil A et al., Ultrasound Obstet Gynecol. 2014;43:413–419), and cavum veli interpositi in the first trimester (Smith E et al.). Clinical interpretation of these findings is not detailed in the fragments [to be clarified].
Related Protocols
Anatomy assessment in the first trimester is supplemented by specialized ISUOG guidelines: fetal cardiac screening (Carvalho JS et al., 2023;61(6):788–803), targeted neurosonography (Paladini D et al., 2021;57:661–671), and management of multiple pregnancy (ISUOG, 2025).
Frequently asked questions
At what gestational age is early fetal anatomy assessment performed according to ISUOG?
The examination is performed at 11–14 weeks; detailed anatomy assessment is possible at 11, 12, and 13 weeks (Luchi C et al.).
Which parameter is used to determine gestational age in the first trimester?
Dating is performed using crown-rump length (CRL); a systematic review of charts is presented by Napolitano R et al. (BJOG. 2014).
Can non-chromosomal anomalies be detected on routine ultrasound at 11–13 weeks?
Yes, routine examination at 11–13 weeks allows diagnosis of a portion of non-chromosomal fetal anomalies (Syngelaki A et al., 2019).
What factors affect the effectiveness of first trimester anatomy screening?
Screening quality factors influence effectiveness; the application of a standardized anatomical protocol increases detection rates (Karim JN et al.; Liao Y et al.).
What findings are described in the first trimester?
Cystic hygroma, fetal edema, abdominal cysts, and cavum veli interpositi; clinical interpretation in the sources is not fully detailed [to be clarified].