Assessment of fetal anatomy at the 11–14‐week ultrasound examination

OBJECTIVE: To assess the feasibility of examining cardiac and non-cardiac fetal anatomy in a low-risk population in the setting of the routine 11-14-week ultrasound scan. METHODS: This was a prospective study of 1144 women with viable, singleton pregnancies at 11-14 weeks of gestation. The ultrasound examination was performed transabdominally and transvaginally and fetal anatomy assessment included visualization of the skull, brain, face, spine, four-chamber and three-vessel views of the heart, stomach, abdominal wall, kidneys, bladder and extremities. RESULTS: Complete examination of the fetal anatomy was achieved in 48% of the fetuses, whereas non-cardiac anatomy was examined successfully in 86% of the fetuses. The use of the transvaginal approach increased successful examination of the fetal anatomy from 72% to 86% of the fetuses and transvaginal scanning was particularly helpful in examining the face, kidneys and bladder. Non-cardiac anatomy visualization increased from 65% for fetuses with a crown-rump length of 45-54 mm, to 84%, 93% and 96% for fetuses with a crown-rump length of 55-64 mm, 65-74 mm and more than 74 mm, respectively. In the same groups the four-chamber view was seen in 67%, 86%, 93% and 97% of fetuses, and the three-vessel view was seen in 25%, 46%, 58% and 67% of fetuses, respectively. Maternal habitus and crown-rump length were found to be statistically significant contributors to the rate of successful examination of fetal anatomy. CONCLUSION: Examination of fetal anatomy is feasible during the routine 11-14-week scan. The optimal gestational age for examining both cardiac and non-cardiac anatomy is from the beginning of the 12th week to the end of the 13th week of gestation. Access to the transvaginal approach is important for completeness of the examination.