All About Obstetric Ultrasound

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This is an article from our “Doctor’s Corner” series, brought to you by Samitivej Hospital. Make sure to read the entire series!

Obstetric ultrasound is a test that assists obstetricians in diagnosing and screening pregnant women for any abnormalities in the fetus, as well as anomalies in the mother’s pelvic organs including the uterus and the ovary. It is a safe procedure as it uses sound waves as opposed to radiation.

All about ultrasound

Types of Ultrasound

2D ultrasound
Creates an image without depth to observe fetal size and any abnormalities of organs, as well as observe the pelvic organs of the mother

3D ultrasound
Creates a virtual still image with depth to be used in conjunction with 2D ultrasound to enhance the effectiveness of diagnosis in case there are abnormalities found in the fetus.

4D ultrasound
Creates a 3D moving image with depth of the fetus’s postures. The objectives of using 4D ultrasound are the same as those of 3D.

Remark: The screening test during pregnancy is principally performed by 2D ultrasound. 3D and 4D ultrasounds are used only when the doctor deems them appropriate.

Looking for a doctor for your pregnancy health questions? We recommend:
Thewin Dejthevaporn, M.D.Thewin Dejthevaporn, M.D.
OB/GYN, Samitivej Hospital
Questions about your pregnancy, child birth or life with an infant? Ask the Doctor!

Gestational Age and Indications

Ultrasound can be performed in every gestational age in accordance with the doctor’s opinion. Appropriate gestational ages for ultrasound are as follows:

5-11 Weeks

  • To confirm a intrauterine pregnancy and diagnosis for a multiple pregnancy
  • To determine the gestational age by measuring the size of the fetus
  • To diagnose excessive bleeding beneath the placenta membrane
  • To diagnose an abnormal pregnancy including ectopic pregnancy, blighted ovum, and molar pregnancy
  • To diagnose myoma uteri and ovarian cyst or tumor

11-13 Weeks and 6 Days

  • To measure the size of the fetus and determine the gestational age
  • To measure fluid accumulation beneath the skin of fetal neck (nuchal translucency). The result of the measurement is used in conjunction with the mother’s blood test for down syndrome screening*
  • To identify the early stages of many disabilities in the fetus
  • To evaluate the mother’s pelvic organs such as the uterus and the ovary

Remark: If the fetus has unusual thickness of nuchal translucency, it is possibly related to down syndrome or other chromosomal abnormalities. In addition, this is possibly related to fetal abnormalities including heart diseases, abnormal limbs, genetic disorders, etc.

18-23 Weeks

  • This is a crucial age and takes the longest to perform ultrasound at 30 minutes-1 hour
  • To screen and diagnose structure-related abnormalities such as of the skull, cerebral tissue, spinal cord, arms, legs, heart, etc.
  • To observe fetal growth, the position of the placenta and estimate the amount of amniotic fluid
  • To observe the length of the cervix in order to determine the possibility of a premature birth

28 weeks until the immediate stage before the delivery*

  • To observe development and determine the weight of the fetus
  • To diagnose fetal growth restrictions
  • To check the position of the placenta, fetal posture and the amount of amniotic fluid
  • To observe the length of the cervix in order to determine the possibility of premature labor
  • To check the health of the fetus by observing its breathing, movement and evaluating amniotic fluid

Remark: If the mother has no risk factors, it is recommended that an ultrasound is performed during the 30-32 weeks. If the mother is at potential risk, having a multiple pregnancy, or complications, it is recommended that the health of the fetus should be evaluated as often as per the doctor’s suggestion.

The Effectiveness and Limits of Ultrasound

Ultrasound tests need water to create an image and depend on the sound waves penetrating through the tissues. Therefore, the effectiveness of ultrasound depends on the amount of amniotic fluid present, the thickness of the mother’s abdomen, obesity, surgical wounds at the abdomen, and the fetus not being ready for the test.

In a study of almost 12,000 Nebraska schoolchildren published in August 2013 in The Journal of Pediatrics, researchers compiled each child’s physical fitness (as measured by a timed run and body mass index) and academic achievement in English and math, based on the state’s standardized test scores. Better fitness was linked to significantly higher achievement scores, while body size had almost no role. Students who were overweight but relatively fit had higher test scores than lighter, less-fit children. Finally, according to a new study in the journal PLoS conducted by researchers from the University of Illinois in the United States, 9 and 10 year-old children who were in better aerobic condition significantly outperformed a less-fit group. These researchers concluded that higher levels of fitness have their greatest impact in the most challenging situations that children face intellectually. In other words, the more difficult something is to learn; the more physical fitness may aid your child in learning it.

If children are to develop and maintain the kind of aerobic fitness that amplifies their ability to learn, they should participate in at least an hour a day of vigorous physical activity. Since school is where children spend so many of their waking hours, it makes very good sense that physical fitness programs should be prioritized in schools. If not enough time is allowed during the school day for physical activity, then parents need to ensure that exercise is obtained every day after-school. In the final analysis exercise really also is an academic activity, so I encourage parents to help their children make it a priority in their daily routine.

Samitivej, We Care!

For further information, please contact:

Child Health Institute
Samitivej Sukhumvit Hospital
2st Floor, Building 2
Tel: 66 (0) 2711-8236-7
Call Center: 66 (0) 2711-8181

Photo Credit: salimfadhley via Compfight cc

Samitivej Womens Health Center

Samitivej Hospitals are world class international health care facilities located in Bangkok, Thailand.

Fully equipped with the state-of-the-art technologies, our innovative Women's Health Center at Samitivej Sukhumvit Hospital provides comprehensive gynecological and obstetrical service for women of all ages.

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