The fetal anatomy scan, sometimes referred to as a Level 2 ultrasound, is a detailed, non-invasive imaging procedure performed during the second trimester of pregnancy. This routine prenatal screening uses sound waves to create images of the developing fetus, allowing healthcare providers to survey growth and structural development. It serves as a comprehensive check of the fetus’s anatomy, systematically surveying for any signs of structural abnormalities or congenital conditions before birth.
The Optimal Timing Window
The standard period for scheduling the fetal anatomy scan is between 18 and 22 weeks of gestation. This four-week window maximizes the visibility and size of the fetal structures. Before 18 weeks, organs are often too small for a complete and accurate examination. The timing around 20 weeks allows the sonographer to obtain clear measurements and visualize complex structures like the four chambers of the heart. The proportion of amniotic fluid to the fetus is also optimal, providing a clear environment for imaging. Receiving the results within this timeframe allows parents and providers to explore further diagnostic testing or specialized care planning if concerns arise.
What the Scan Seeks to Measure and Examine
The detailed survey involves a systematic, head-to-toe evaluation of the developing fetus, covering biometric measurements and organ anatomy. The sonographer captures specific images to assess the growth rate and structural integrity, confirming that the fetus is developing appropriately for its gestational age. Biometric measurements establish the fetus’s estimated size and weight. The technician measures the head circumference (HC), the biparietal diameter (BPD), the abdominal circumference (AC), and the femur length (FL). These data points are compared against established growth curves to assess general development.
The scan includes an extensive survey of the fetal anatomy, beginning with the brain and face. The technician examines the structures of the brain, including the cerebellum and ventricles, to ensure proper formation and symmetry. The face is checked for a cleft lip or palate. The spine is evaluated for alignment and integrity to rule out conditions like spina bifida.
A detailed examination of the fetal heart is also performed, visualizing the four chambers and the outflow tracts (the main vessels leaving the heart). The sonographer assesses the chest, lungs, and abdominal organs like the stomach, kidneys, and bladder. The limbs (arms, hands, legs, and feet) are checked for overall structure, symmetry, and the presence of digits.
In addition to the fetus, the anatomy scan assesses the supporting structures of the pregnancy. The location of the placenta is mapped to determine if it is positioned low in the uterus (placenta previa), which can influence delivery planning. The umbilical cord is examined to confirm the presence of three vessels (two arteries and one vein) and its insertion point. The volume of amniotic fluid surrounding the fetus is also measured to ensure levels are within the expected range.
Preparing for the Ultrasound and the Examination Process
Preparing for the anatomy scan is generally straightforward, but some clinics may have specific instructions regarding bladder fullness. While a full bladder was traditionally requested to help push the uterus up for a clearer view, this requirement varies by facility and gestational age, so it is best to confirm with the provider beforehand. The appointment is a medical procedure and can last anywhere from 30 to 60 minutes due to the number of images and measurements required.
During the procedure, the patient lies on an examination table, and a water-soluble gel is applied to the abdomen. A sonographer uses a handheld device called a transducer, moving it across the abdomen to capture real-time images of the fetus using sound waves. The sonographer must often freeze the screen to obtain specific, precise measurements of the structures being evaluated.
The sonographer’s primary focus is gathering high-quality images for the physician to interpret, which sometimes means they remain quiet while concentrating on the systematic image capture. After the scan is complete, the images are reviewed, typically by a specialized physician who then communicates the findings to the patient’s care team. A normal scan provides reassurance about fetal development, while any findings that require further attention will lead to a discussion about follow-up testing or consultation with a specialist.