The components of the standard fetal examination at 18 to 20 weeks have been agreed upon by several organizations and outlined in the ACR-ACOG- AIUM-SMFM-SRU Practice Parameter for the Performance of Standard Diagnostic Obstetrical Ultrasound [8,30]. A routine diagnostic US may be used in the third trimester, either selectively or in the setting of a late arrival for assessment. Bricker et al [31] reviewed 13 trials with 34,980 patients and showed no evidence of improved antenatal, obstetric, or neonatal outcome or morbidity in those screened in the third trimester versus controls. A study by Manegold et al [32]; however, showed third trimester US to have utility for perinatal management and postnatal follow-up, with 15% of all anomalies found only in the third trimester in a study of 8,074 fetuses. Variant 2: Second and third trimester screening for fetal anomaly. High-risk pregnancy. Initial imaging. Detailed fetal anatomic examinations are performed in high-risk pregnancy instances where there is increased risk for anatomic or karyotypic fetal abnormality based on maternal factors (including age, use of in vitro fertilization, drug dependence, infection, or other maternal medical conditions) or abnormality of screening testing (including the quad screen, NIPT, or US findings). The category of high risk also includes family history of genetic disease or abnormality, multi-gestational pregnancies, and teen pregnancies [33]. A German study looked at teenage pregnancies in a database of all pregnancies from 2000 to 2011 and found 638 pregnancies in women <20 years of age, with a total of 9.2% of patients having anomalies or aneuploidy [34]. Obese patients deserve special consideration as rates of congenital anomalies are increased, particularly involving neural tube defects, cardiovascular anomalies, cleft lip or palate, anorectal atresia, hydrocephaly, and limb reduction anomalies [35,36].
Second and Third Trimester Screening for Fetal Anomaly. The components of the standard fetal examination at 18 to 20 weeks have been agreed upon by several organizations and outlined in the ACR-ACOG- AIUM-SMFM-SRU Practice Parameter for the Performance of Standard Diagnostic Obstetrical Ultrasound [8,30]. A routine diagnostic US may be used in the third trimester, either selectively or in the setting of a late arrival for assessment. Bricker et al [31] reviewed 13 trials with 34,980 patients and showed no evidence of improved antenatal, obstetric, or neonatal outcome or morbidity in those screened in the third trimester versus controls. A study by Manegold et al [32]; however, showed third trimester US to have utility for perinatal management and postnatal follow-up, with 15% of all anomalies found only in the third trimester in a study of 8,074 fetuses. Variant 2: Second and third trimester screening for fetal anomaly. High-risk pregnancy. Initial imaging. Detailed fetal anatomic examinations are performed in high-risk pregnancy instances where there is increased risk for anatomic or karyotypic fetal abnormality based on maternal factors (including age, use of in vitro fertilization, drug dependence, infection, or other maternal medical conditions) or abnormality of screening testing (including the quad screen, NIPT, or US findings). The category of high risk also includes family history of genetic disease or abnormality, multi-gestational pregnancies, and teen pregnancies [33]. A German study looked at teenage pregnancies in a database of all pregnancies from 2000 to 2011 and found 638 pregnancies in women <20 years of age, with a total of 9.2% of patients having anomalies or aneuploidy [34]. Obese patients deserve special consideration as rates of congenital anomalies are increased, particularly involving neural tube defects, cardiovascular anomalies, cleft lip or palate, anorectal atresia, hydrocephaly, and limb reduction anomalies [35,36].