Introduction: The ultrasound scan is a specialized medical technique that uses high frequency sound waves beyond normal human hearing capacity. It is of immense value in pregnancy enabling us to visualize the developing baby. Recent advances in this technique allows us to have clearer and higher quality examinations of the baby. The information derived from these examinations are thus important in the successful management of the pregnancy.

Who should carry out ultrasound/fetal evaluation scans?
Ultrasound scan services, being a specialized imaging medical technique, requires training, experience and requisite certification by recognized accrediting bodies. This will prevent patients from having substandard services and unreliable results as has often occurred. There are various levels of ultrasound scan services especially as it relates to the field of Fetal Medicine which is a more specialized field dealing with very high level fetal diagnosis. For very high level scans, it is expected that the sonographer has had:

  • Basic training and certification in radiology or sonography at an accredited institution recognized in the country
  • A specialist in Obstetrics/Gynecology with special interest and training in maternal-fetal medicine
  • A medical practitioner who has had certified training in fetal medicine.
  • A practitioner who has acquired international certification and listing by the Fetal Medicine Foundation (UK). The list of those certified worldwide is available by country  on line at

Requirements for a good ultrasound service

  • A good ultrasound machine
  • Trained and certified ultrasound personnel with adequate knowledge, skill and experience
  • A well filled referral form that details the indication and the risk factors for any problem in the pregnancy.

Types of ultrasound scan examination
Transabdominal: Here, the sonologist uses a transabdominal probe placed on the surface of the abdomen. This allows a wide range of the structures in the abdominal cavity to be seen with reasonable clarity. The developing baby and the surrounding structures can all be seen and assessed. Often times, it is necessary for the woman to be “pressed to urinate” prior to this examination. The urinary bladder then serves as a window for clearer visualization of the internal structures. It is often distressing as the patient drinks a lot of water before the examination. A drawback of the transabdominal scan is that it may not give good quality views of small organs like the ovaries in the pelvis especially in the non pregnant woman. Also, it may be difficult to accurately ascertain the position of the placenta and the anatomy of the cervix.

Transvaginal: Here, the sonologist uses a probe which is inserted in the vagina. To prevent transfer of infection, the probe is covered with a condom before being inserted.  The transvaginal probe gives a clearer view of the structures in the pelvis but cannot see the structures that are deeper. The transvaginal scan therefore gives better views of fewer structures. It is very useful in viewing the ovaries and cervix and sometimes the lower part of the placenta. It is also of importance in early pregnancy assessment to determine the location of the pregnancy. Another notable advantage of the transvaginal scan is that the woman is spared the discomfort of a full bladder as an empty bladder is what is required for this scan.


Safety of ultrasound examination
Concerns have been raised about the safety of ultrasound examination. However, no harmful effect has been found to date despite its widespread use. Besides, every trained sonographer knows the ALARA principle of ultrasound use. The ALARA principle is an acronym that uses the first letter of the basic safety principles viz As Low As Reasonably Achievable. This implies that any trained sonographer has a duty towards the patient not to use or exceed levels of ultrasound that are above the levels proven to be safe for the fetus Therefore, in knowledgeable hands, ultrasound can be considered safe.

Advantages of obstetric ultrasound scan

  1. It confirms the pregnancy and the location.
  2. It gives reassurance and joy to the family of the presence of the pregnancy, its growth and health. However, this is not a 100% as not all abnormalities can be seen on scan.
  3. If done early in pregnancy, it can give, to a reasonable degree of accuracy, the expected date of delivery.
  4. It helps to diagnose how many babies there are and what type of multiple pregnancy. This is important in planning care for the expectant mother instead of blind treatment.
  5. There is early bonding between the mother and her unborn baby and the family.
  6. It is a form of social interaction with the family present at the scan.
  7. It may provide the first picture of the baby in the womb (optional).

Disadvantages of obstetric ultrasound

  1. Ultrasound scan may elicit some anxiety in the parents especially if some abnormal findings are seen. However, most babies are found to be normal and only a small fraction of babies have significant abnormalities
  2. It is time consuming. (Pre-booking at the center can save you time as you come on appointment).
  3. It may be expensive depending on where and why the scan is being done.
  4. False reassurance if there is poor counseling. Some abnormalities do not show at ultrasound. Fortunately, this is quite rare.

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