Usefulness of antenatal ultrasound fetal morphological assessments in the first and second trimester: a study at a single Japanese university hospital

Objective: To assess the usefulness of antenatal ultrasound examinations for detecting fetal morphological abnormalities in the first and second trimesters. Methods: A prospective cohort study was conducted at a single Japanese university hospital in the period from February 2011 to September 2013. Patients in whom ultrasound was attempted at both 11 to 13 + 6 and 18 to 20 + 6 weeks’ gestation and who were delivered at our hospital were enrolled. After delivery, neonatal congenital abnormalities were reviewed and compared with the ultrasound findings in the first and second trimesters. Results: The subjects were 2028 singleton babies. Abnormal fetal morphological findings were found in the first trimester in 28 cases. In these patients, fetal anomalies detected as diagnostic findings were anencephaly (2 cases) and endocardial cushion defect (2 cases). Findings suggestive of fetal anomalies were observed in 24 cases in the first trimester. Twelve cases with ultrasound findings in the first trimester, including fetal edema, anencephaly, endocardial cushion defect, exhibited an abnormal chromosome after amniocentesis. Ultrasound findings in the first trimester disappeared until 18 weeks of gestation in eight cases, and they were preserved in three cases. Fetal anomalies were primarily noted in the second trimester in 10 cases. However, after delivery, morphological abnormalities were primarily observed in 18 cases. Conclusion: Major congenital abnormalities were identified in the first trimester morphological assessment. We think the use of a combination of the first trimester ultrasound screening and the second trimester ultrasound scan for detecting fetal anomalies was effective.