General Guidelines on 2D, 3D & 4D Scans

What is an ultrasound / scan?

A pregnancy ultrasound or scan, is an imaging test that uses sound waves to see how a baby is developing in the womb. These scans are used during the course of the pregnancy to monitor fetal growth and development.  Ultrasound waves cause no harm to the mother or fetus

There are two types of ultrasound examinations:

Trans-vaginal ultrasound
A small ultrasound probe is inserted into the vagina and rests on the cervix to create an image of the early 6-12 week pregnancy and the maternal pelvic organs (uterus and ovaries).

Abdominal ultrasound
The ultrasound probe is placed on the lower abdomen to examine the larger uterus containing fetus, placenta & amniotic fluid, in a pregnancy from 12 weeks onwards.

Why are scans performed in pregnancy?To:

  • Diagnose an intra-uterine pregnancy.
  • Diagnose a miscarriage.
  • Determine presence of multiple fetuses.
  • Diagnose normal fetal & placental development.
  • Diagnose birth defects.
  • Assist in prenatal tests such as an amniocentesis.
  • Determine size and position of a fetus late in the pregnancy.
  • Determine the gender of the fetus.

Are all scans the same?
Some things are looked at in every scan, others relate to pregnancy duration & fetal size. Every scan should document the number of fetuses, the fetal heart beat, the size of the fetus and development of the fetal organs. The scan will also check the position of the placenta (afterbirth) and the amount of fluid around the fetus (amniotic fluid). This will always be done using 2D scans.

While measuring and examining the fetus, one can sometimes detect the development of structural abnormalities in the fetus. Fortunately most fetuses are normal but in about 5% an abnormality is present. Some defects are minor, others severe or fatal. Not all parents want to know before the birth whether their fetus is normal or not because they may feel too upset when a problem is detected many weeks before the birth. This can be very distressing to parents. To look for abnormalities in the fetus is therefore optional. If you don’t want to be informed about any abnormal findings in the fetus, you must tell the person examining you before the scan is started.

Do I need a full bladder?

The shape of the modern probes means that the scan can be done with an empty bladder. Try not to drink too much fluid prior to the scan.

Can I bring family to see the ultrasound?

Husbands or partners are always welcome in the ultrasound room. Family members & children are not allowed into the examination room. This is because they might be a distraction to the sonographer and the scan may take anything from 30-60 minutes. They are welcome to join in the last 5 minutes of the examination when everything has been checked.

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