During what time frame are most congenital abnormalities detected during pregnancy?

The correct choice highlights that most congenital abnormalities are typically detected between 18 and 20 weeks of gestation during an anatomy ultrasound, often referred to as a mid-pregnancy or second-trimester ultrasound. This ultrasound is comprehensive and usually assesses fetal anatomy in detail, allowing for the identification of structural abnormalities such as neural tube defects, congenital heart defects, and other physical malformations.

This timeframe is critical because, by this point in pregnancy, the fetus has developed enough for many abnormalities to be visualized clearly via ultrasound, leading to more accurate assessments. Early first-trimester screenings, such as blood tests, focus primarily on the assessment of risk for chromosomal abnormalities but are not as effective for identifying structural issues.

Additionally, the use of Doppler ultrasound later in pregnancy mainly aids in assessing fetal well-being, blood flow, and placental function rather than directly visualizing congenital abnormalities. Lastly, physical examinations after birth can identify congenital issues, but they are not proactive; the detection during pregnancy through ultrasound allows for informed decision-making regarding management and care prior to delivery.