Benefits of Ultrasound Examination During Pregnancy
Ultrasound examination during pregnancy is useful for detecting abnormalities in the fetal body structure and key structures including the placenta, umbilical cord, amniotic fluid, skull, brain tissue, arms, legs, chest cavity, lung tissue, heart, abdominal wall, and major internal organs in the abdominal cavity. Measuring the size of the fetus through ultrasound also helps confirm gestational age and determine the due date in cases where the mother has irregular or no menstrual periods, which is very beneficial for care during the late pregnancy period. It helps prevent post-term pregnancy, which may adversely affect the health of the fetus.
Additionally, ultrasound allows the mother to see images of the baby moving in the womb, fostering love and bonding even before birth (Maternal – fetal Bonding). Many European countries have policies recommending that all pregnant women undergo at least one ultrasound examination during the mid-pregnancy period to screen whether the fetus is developing normally (Mid – trimester Screening).
However, ultrasound has limitations. Some abnormalities cannot be diagnosed, especially those involving very small organs, certain types of congenital heart defects, or the function of various organs.
Moreover, ultrasound requires fluid for reflection quality and depends on the distance the sound waves travel through tissues. Therefore, the quality of the examination decreases in cases with certain limitations such as too little or too much amniotic fluid, a thick or obese maternal abdomen, abdominal surgical scars, and unfavorable fetal positions for examination.
Types of Ultrasound
- 2D Ultrasound
This produces a single-plane image without depth, used to check the size and abnormalities of various organs and blood flow of the fetus, along with examining the mother’s pelvic internal organs.
- 3D Ultrasound
This produces realistic still images with depth. It is used in conjunction with 2D ultrasound to enhance diagnostic efficiency when abnormalities in the fetus are detected.
- 4D Ultrasound
This is the latest technology, producing moving 3D images. It allows in-depth viewing of fetal movements and postures. The purpose is similar to that of 3D ultrasound.
Note: Screening during pregnancy primarily uses 2D ultrasound. The use of 3D or 4D ultrasound is considered additionally based on appropriateness.
Recommended Gestational Age and Indications
Ultrasound can be performed at any stage throughout pregnancy as determined by the physician. The recommended gestational periods for ultrasound examination are as follows:
Gestational Age 5-11 Weeks
- To confirm intrauterine pregnancy and differentiate twin pregnancies
- To assess and determine gestational age by measuring the fetus
- To diagnose abnormal bleeding from beneath the placental membrane
- To diagnose abnormal pregnancies such as ectopic pregnancy, blighted ovum, or molar pregnancy
- To diagnose uterine tumors and ovarian cysts or tumors
Gestational Age 11-13 Weeks 6 Days
- To measure fetal size to determine gestational age
- To measure nuchal translucency thickness under the skin at the back of the fetal neck, used in conjunction with maternal blood test results for screening Down syndrome*
- To preliminarily diagnose several severe fetal abnormalities
- To assess maternal pelvic organs such as the uterus and ovaries
If the nuchal translucency is abnormal, it may be associated with Down syndrome and various chromosomal abnormalities. It may also be related to fetal organ defects such as heart disease, limb deformities, and genetic disorders.
Gestational Age 18-23 Weeks
This is an important period and the examination takes the longest time, approximately 30 minutes to 1 hour.
- Screening and diagnosing structural abnormalities of fetal organs such as the skull, brain tissue, spinal cord, arms, legs, and heart
- Checking fetal growth, placental position, and assessing amniotic fluid volume
- Measuring cervical length to predict the risk of preterm labor
Gestational Age from 28 Weeks to Near Delivery
- Checking fetal growth and estimating fetal weight
- Diagnosing fetal growth restriction
- Checking placental position, diagnosing placenta previa, assessing fetal presentation, and amniotic fluid volume
- Assessing fetal health by observing fetal breathing, movements, and amniotic fluid status
- For mothers without risk factors, it is recommended to have an ultrasound at 30-32 weeks gestation
- For high-risk pregnancies, multiple pregnancies, or complications, more frequent fetal health assessments should be performed as determined by the obstetrician
