The routine ultrasound is usually performed between weeks 18 and 20 of pregnancy. It is a medical examination designed to assess basic fetal anatomy, determine gestational age, confirm the number of fetuses and evaluate the position of the placenta. The examination follows a structured method where different parts of the fetal body are visualised and documented.

Unlike first-trimester ultrasound, crown-to-rump length is not measured. Instead, measurements such as head circumference, biparietal diameter (distance between the temples), abdominal circumference and femur length are used. These are compared with gestational age to assess whether fetal growth follows the expected pattern.

Basic anatomical structures are evaluated, including brain contours, spine alignment, facial profile, abdominal wall, kidneys and bladder. The heart is examined in basic form, focusing on position and chamber symmetry. The goal is to confirm that organs are present and structurally positioned as expected. Organ function is not assessed during this scan.

The position of the placenta is documented, including whether it lies near or away from the cervical opening. The amount of amniotic fluid is visually estimated, but not measured with exact volume.

The routine ultrasound is a structural examination — not focused on function, behavioural activity or movement patterns.