The anatomy scan, often referred to as the mid-pregnancy ultrasound, is a detailed examination typically performed between the 18th and 22nd weeks of pregnancy. This appointment differs from many other medical procedures because fasting is generally not required, and in fact, eating is often recommended. Preparation for this approximately hour-long appointment is focused on encouraging fetal movement and optimizing image clarity. The goal is to ensure the sonographer can capture all the necessary images to complete a thorough assessment.
What the Anatomy Scan Examines
This comprehensive imaging session is a head-to-toe evaluation of the developing baby’s structure. The sonographer systematically checks the size and growth of the fetus by measuring various parts, including the head circumference, abdominal circumference, and the length of the femur. These measurements help determine if the baby is growing at an expected rate for its gestational age.
A major focus of the scan is the detailed examination of major organ systems. This includes visualizing the four chambers of the heart, checking the integrity of the spine, and confirming the presence and proper formation of the kidneys, bladder, and stomach. The brain structure is also carefully assessed to look for key landmarks and rule out certain neural tube defects.
The scan also provides important information about the environment surrounding the fetus. The sonographer will check the location of the placenta, noting whether it is positioned low in the uterus, and verify the number of blood vessels in the umbilical cord. The volume of amniotic fluid is measured, as this fluid is necessary for the baby’s lung development and overall well-being.
Eating and Drinking Guidelines for Optimal Results
Unlike blood work or certain abdominal scans, eating before the anatomy scan is not only permitted but actively encouraged by many providers. A primary reason for this advice is that a slight elevation in maternal blood sugar can sometimes stimulate fetal activity. This increased movement helps the baby shift positions, which is often necessary for the sonographer to obtain clear pictures of all the required anatomy.
It is generally advised to eat a light, healthy meal about one to two hours before the scheduled appointment. A meal containing a balance of nutrients can provide the steady energy needed for both the mother and the baby during the lengthy scan. Avoiding an overly large meal is sensible, however, as lying flat on the back for an extended period after a heavy meal can sometimes cause maternal discomfort.
In addition to a meal, many clinics suggest consuming a beverage containing a small amount of sugar or caffeine approximately 15 to 30 minutes before the scan begins. This short-term energy boost encourages the baby to wake up and move away from a curled position. Options include a small glass of juice, a non-carbonated soda, or an iced drink, as the cold temperature can sometimes prompt a reaction.
Hydration is another consideration, as sufficient fluid intake helps maximize the clarity of the ultrasound images. Being well-hydrated contributes to a larger volume of amniotic fluid and helps the sound waves travel more effectively through the maternal tissues. Maintaining good fluid intake throughout the day leading up to the appointment is beneficial.
Other Important Preparation Steps
Beyond food and drink, the most common preparation instruction relates to the fullness of the maternal bladder. For many second-trimester ultrasounds, a full or partially full bladder is required at the start of the exam. The fluid in the bladder helps push the uterus slightly higher into the abdomen, improving the visibility of the lower uterine segment and the baby’s position in the pelvis.
The specific requirement for bladder fullness can vary significantly between imaging centers and is often dependent on the stage of the pregnancy. Some technologists may ask the patient to drink a specific amount of water, such as 16 to 32 ounces, an hour before the scan. Once initial images are captured, the bladder can be emptied, as a full bladder is no longer necessary once the uterus has risen out of the pelvis.
Preparing for the scan also involves considering the attire and timing of the appointment. It is helpful to wear loose-fitting, comfortable clothing, preferably a two-piece outfit, so the abdomen can be easily exposed. Since the detailed scan can take anywhere from 30 to 60 minutes, arriving 10 to 15 minutes early is recommended to complete any necessary paperwork. Patients should also confirm the clinic’s policy on bringing partners or other guests into the examination room.
What Happens If the Baby Isn’t Cooperating
Despite careful preparation, babies frequently prove to be uncooperative during the anatomy scan by positioning themselves poorly or falling asleep. Common uncooperative positions include facing the mother’s spine, curling up in a tight ball, or obscuring the face or heart with hands or feet. When this occurs, the sonographer cannot obtain the required detailed measurements needed to complete the official report.
If the baby is not cooperating, the technologist employs several immediate techniques to encourage movement. These actions can sometimes wake the baby or prompt a shift in position that allows for a clearer view. Techniques include:
- Gently pressing on the abdomen with the transducer.
- Asking the mother to change positions.
- Having the mother get up to walk around.
- Doing a few light movements, like jumping jacks.
If these immediate interventions are unsuccessful, the patient will be asked to return for a follow-up appointment, sometimes called a re-scan. This necessity is quite common and is usually not a sign of a problem with the baby’s development. The re-scan is simply scheduled to capture the few remaining images that were missed, providing the medical team with the complete anatomical survey.