Many expectant mothers first undergo a routine prenatal ultrasound to check the fetal size, heartbeat, fetal position, amniotic fluid volume, and placental location. Structural ultrasound, on the other hand, is a specialized ultrasound examination designed to comprehensively examine the fetal structure. This includes determining the fetus's sex, as well as examining the skull, intracranial structures, eye sockets, spine, heart, lungs, diaphragm, stomach, gallbladder, bladder, umbilical cord, and limbs — a very comprehensive examination, essentially a head-to-toe check. This allows for the detection of structural malformations in a small percentage of infants before birth. Understanding these abnormalities can then facilitate prenatal diagnosis and screening for genetic or hereditary abnormalities. If a serious congenital defect is discovered, resulting in severe disabilities or even a high risk of death after birth, parents must prepare for the affected infant. In severe cases, termination of pregnancy may be necessary.

Structural ultrasound can diagnose approximately 80% of serious congenital structural abnormalities, such as spina bifida, anencephaly, and limb abnormalities. However, the following conditions may be more difficult to diagnose with structural ultrasound:

1. Functional deficiencies, such as blindness, deafness, or intellectual disability.

2. Some minor structural defects were discovered, such as a small cleft palate and minor heart septum defect

3. Some defects do not have obvious ultrasound characteristics. For example, anal obstruction and Down’s syndrome are among them.

However, if the fetus has problems such as small bowel obstruction or dwarfism, these conditions will only become apparent in the late stages of pregnancy or after delivery. A structural ultrasound examination during the second trimester may not be able to confirm the condition. Therefore, if the expectant mother has a family history of such conditions and is concerned that the fetus may have a genetic disease, she can discuss it with her doctor and undergo further screening or diagnosis using other tests .

After a pregnant woman's first structural ultrasound (usually between 18 and 22 weeks of pregnancy, or earlier), if both she and the fetus are found to be normal, no further examinations are necessary. However, if potential problems are detected, such as kidney distension, the pregnant woman will need another structural ultrasound at 28 weeks of pregnancy. If the fetal heart is not clearly visible during the initial examination, the pregnant woman will need to have another examination every 1 to 2 weeks. Because structural ultrasounds are generally difficult to book at public hospitals (as public hospitals prioritize older mothers or higher-risk pregnancies), it is best to register at private hospitals or clinics. To ensure timely appointments, structural ultrasound doctors recommend that pregnant women begin scheduling appointments after 10 weeks of pregnancy to ensure the most appropriate time for the examination.

Structural ultrasound examinations in early pregnancy are generally performed between 12 and 14 weeks of gestation. This earlier examination has several advantages, such as the ability to detect abnormal markers early, allowing for prenatal diagnosis based on genetic or hereditary factors; it also allows for medical consultations based on relevant medical conditions.

However, early pregnancy fetal structural ultrasound also has some limitations. This examination can detect only about 50% of all structural abnormalities. In the early stages of pregnancy, although fetal organs continue to develop, they are still very small, and some structural abnormalities may not be obvious, only becoming apparent in later pregnancy. Furthermore, some suspected structural abnormalities may not be detected during early pregnancy structural ultrasound. In such cases, further structural ultrasound examinations are usually required several weeks later to confirm or overturn the previous diagnosis. In addition , the accuracy of fetal examinations in early pregnancy depends on many factors, including the severity of the abnormality and the position of the fetus. Therefore, fetal structural ultrasound examinations in mid-pregnancy are needed to provide clearer results .

To understand the principle of 4D structured ultrasound, it uses a large number of 2D images, processes them, and then presents a 3D short film. From this film, you can see the fetus's movements; you can usually see their hands and feet moving freely, and sometimes even see them actively moving within the amniotic fluid. Of course, you can also see the baby's organs to determine its sex, as well as its head and appearance (such as eyes, ears, mouth, nose, etc.), its body structure and internal organ development, and you can even hear the fetal heartbeat.

Structural ultrasound examinations may not be 100% accurate, their accuracy is extremely high. In fact, although structural ultrasound may not detect all congenital defects, over 80% of congenital structural abnormalities can generally be detected around 20 weeks of gestation. The accuracy depends on several factors, including the degree and nature of the fetal abnormality; the fetal position; the mother's condition (e.g., the thickness of the subcutaneous fat layer); the technical quality of the ultrasound equipment; and the qualifications and experience of the medical staff. Our Hong Kong S&B Medical Center's doctors and medical staff performing structural ultrasounds are among the most experienced and professional, and we use advanced equipment, making us the recommended choice for structural ultrasound examinations.

Structural ultrasound doctors typically advise pregnant women to drink three glasses of water an hour before the examination and then hold their urine. This ensures a full bladder, making it easier to visualize the ultrasound images. Some doctors also suggest that pregnant women can eat normally beforehand, but should not empty their bladder within 30 minutes of the examination. In short, following the instructions of the doctor and medical staff before the examination will result in more accurate results. During the examination, the structural ultrasound doctor or other medical staff will apply gel to the pregnant woman's abdomen and pelvic area. Therefore, on the day of the examination, pregnant women should not use any creams or other skin care products on these areas. Comfortable, loose clothing is recommended for the examination.

Structural ultrasound examinations are not routine procedures in public hospitals and are only offered by some public hospitals to pregnant women of advanced age or with a history of genetic diseases or other high-risk conditions. Therefore, low risk pregnant women who wish to undergo structural ultrasound examinations must pay additional fees to have them performed at private hospitals or clinics. The fees charged by these private medical institutions generally range from HK$3,000 to HK$7,000. Some fees may include the ultrasound technician 's consultation fee. The exact cost will depend on the pregnant woman's health condition and the individual hospital or clinic's pricing. For example, 3D or 4D examinations are more expensive than 2D examinations; the prices listed above are generally for singleton pregnancies, and the costs will be even higher for twins, triplets, etc. Our clinic 's fees for these examinations are similar to those of other private medical centers. Please feel free to inquire.

Not necessarily. Some congenital defects in fetuses can be diagnosed directly through structural examination, but others require further investigation to rule out more serious conditions. If a congenital defect is unfortunately discovered, doctors will usually arrange further follow-up, such as a repeat structural ultrasound examination a few days later. If the defect persists, they will contact relevant specialists for appropriate treatment. Geneticists and pediatric surgeons, for example, will follow up with pregnant women in need so that the baby can receive appropriate treatment after birth and gradually recover and grow healthily. However, if the fetus has a fatal congenital defect that will not be cured after birth, forcing them to live with severe disabilities or even die young, the pregnant woman can choose to have an abortion before 24 weeks of pregnancy to legally terminate the pregnancy.

In fact, this prenatal ultrasound examination has been used for diagnostic purposes since the 1960s. Numerous studies on fetuses who underwent ultrasound examinations before birth and into childhood indicate that there is currently no evidence that ultrasound examinations have adverse effects on the fetus; expectant parents can rest assured.