The anatomy scan, often referred to as a Level 2 ultrasound, is a routine, non-invasive procedure performed during the second trimester of pregnancy. This detailed examination provides a comprehensive look at the developing fetus. Preparing correctly for this appointment is important, and specific hydration instructions are often required to ensure the highest quality images are captured. This article focuses on the necessary fluid intake and timing for preparation.
Understanding the Anatomy Scan
The anatomy scan is a systematic, detailed medical imaging procedure typically scheduled between 18 and 22 weeks of gestation. This timing allows the sonographer to obtain precise measurements because the fetus is large enough for detailed viewing. The primary goal of the scan is to evaluate the fetal anatomy for normal development and to check for any structural anomalies.
During the 30 to 45-minute examination, the sonographer assesses various fetal structures. These checks include measuring the head circumference, abdominal circumference, and femur length to confirm growth aligns with the gestational age. The sonographer also systematically examines the four chambers of the heart, the brain, the spine, the kidneys, and the stomach.
Beyond the baby’s development, the scan also focuses on the overall uterine environment. This includes assessing the location and appearance of the placenta, which provides nutrients and oxygen to the fetus. The amount of amniotic fluid surrounding the baby is also measured, and the health of the umbilical cord is checked.
Specific Hydration Requirements: Amount and Timing
To ensure the best possible images are captured during the transabdominal scan, specific hydration is required. The recommended volume of water generally falls within the range of 24 to 32 ounces (three to four standard glasses). Consume this fluid slowly, starting approximately 60 to 90 minutes before the scheduled appointment time.
This timing allows the water to be metabolized and the bladder to fill completely just as the examination begins. Once the fluid is consumed, avoid emptying the bladder until the sonographer confirms they have completed the necessary imaging. If a patient is already well-hydrated, a slightly smaller volume may be sufficient to achieve a full bladder.
Non-carbonated, clear water is the preferred beverage, as fizzy drinks can introduce gas into the digestive tract. The required volume can vary based on the imaging center’s protocol and the patient’s individual hydration status. If the bladder becomes uncomfortably full, some centers may allow the patient to partially void a small amount, but this must be done with staff approval.
Why a Full Bladder is Essential for Imaging Quality
The requirement for a full bladder is rooted in the physics of ultrasound technology. Ultrasound uses high-frequency sound waves that travel through the body to create images. These sound waves transmit easily through fluid, but they are scattered or blocked by air or gas.
In the pelvis, a full, fluid-filled bladder acts as an effective “acoustic window.” This liquid medium allows sound waves to travel with minimal resistance, resulting in clearer, higher-quality images of the structures behind it. The full bladder also helps to push the uterus upward, slightly out of the pelvic cavity.
The upward push displaces gas-filled bowel loops that typically sit in the lower abdomen. Moving the bowel out of the imaging path ensures a clear, unobstructed view for the sonographer, as gas interferes significantly with sound wave transmission. This clear path is important for accurately visualizing the lower uterine segment, the cervix, and the position of the placenta.
Additional Preparation and Troubleshooting
Beyond hydration, several other preparation steps ensure a smooth and successful anatomy scan. It is recommended to eat a light, healthy meal or snack before the appointment. Maintaining stable blood sugar levels can encourage fetal movement, which is beneficial if the baby is in a difficult position for measurement.
Choosing appropriate clothing enhances comfort and efficiency during the scan. Wear comfortable, two-piece outfits, such as a shirt and pants or a skirt. This allows the sonographer to easily access the abdomen without the need to fully undress.
If the bladder is not full enough to obtain adequate images, the sonographer may ask the patient to drink more water and wait. Conversely, if the patient is in extreme discomfort due to an overly full bladder, the technician may allow a partial void. Open communication with the sonographer about comfort levels is advised to ensure necessary images are captured while minimizing distress.