Are frequent ultrasound scans safe?

In last month's Samitivej column, we looked at high-risk pregnancy and explained how an ultrasound is used to detect foetal abnormalities.

Many women, not just those at high risk, will have one than one ultrasound during their pregnancies and some of them wonder just how safe the procedure is.

Ultrasound is defined as any sound above the frequency limit of audible hearing, which is 20,000Hz, Normally, we can hear the sound range 20 - 20,000 Hz. Likewise, the baby cannot hear beyond this range. Ultrasound is safe because the body is not exposed to a ray. No cases have ever been recorded of any dangers caused by ultrasound during the almost 50 years since its first application. It is safe to perform ultrasound scans as many times as necessary on the advice of the doctor.

There are three main stages of the pregnancy when an ultrasound scan is important:

In this first trimester (6th-12th week) to confirm the gestational age
The second trimester (16th 22nd week) to check and screen for any abnormalities of the organs
The third trimester (32nd-36th week) to assess the baby's development and surroundings, including the placenta, amniotic water, and the health of the baby
A 2-dimensional ultrasound provides two- dimensional images of width and length. The image shown is made up of horizontal sound wave while a 3-dimensional ultrasound uses 2D images to construct 3D images.

The 3D images include depth as well as width and length.

A 4-dimensional ultrasound uses the 3D images to construct more virtual and moving images. The result is like that of a video.

The American College of Obstetricians and Gynaecologists offers the following description of how ultrasound is used in pregnancy:

To confirm a pregnancy and determine whether the pregnancy is ectopic or not

To confirm the gestational age in case the mother does not remember when her latest period was

To check when the mother has bleeding without any obvious cause

To evaluate the growth of the baby

To check whether or not there are twins

To see the position of the baby

To check whether or not the mother has a molar pregnancy

To check whether or not the baby is still alive / The Nation