Ultrasound has been used in obstetrics since the late 1950’s and early 1960’s. However we are now in an age where ultrasound is offered to every woman, often multiple times during pregnancy. In fact, 3-D ultrasound photos are desired by a growing number of parents and celebrities even purchase ultrasound equipment to use at home. We can only wonder at the safety of this prenatal testing device being used so frequently and for what are clearly not medical reasons. What do we truly know about ultrasound, its benefits and uses, as well as its safety for pregnancy?
Ultrasound in Pregnancy
A basic ultrasound can be used to confirm pregnancy as early as 5 ½ weeks, determining gestational age of the baby as well as to check for location of the placenta. A woman might need a comprehensive ultrasound to checking for the baby’s health around 18-20 weeks or as a follow-up to any of the above tests.
Ultrasound is also used in conjunction with other prenatal tests such as amniocentesis and the nuchal fold translucency. Some providers may also recommend an ultrasound to check on the baby’s growth during pregnancy or to see of the baby’s lungs are mature for delivery near the end of pregnancy.
How Does Ultrasound Work?
A prenatal ultrasound uses high frequency sound waves which are transmitted through the mother’s abdomen and creates an “echo” where the sound waves bounce off the object, or in this case, the part of the baby they are examining.
Who Performs Pregnancy Ultrasound?
Either your obstetrician or a certified ultrasound technician can perform an ultrasound. If you are having a standard ultrasound, you will typically need a full bladder to help eliminate air pockets between your bladder and uterus. Typically a water-based gel is used with the ultrasound transducer since liquid is a good conductor of sound.
Ultrasound and Estimating Weight of Baby
A sonographer will take various measurements during an ultrasound including: Head circumference, measurement from one side of the head to the other (biparietal), Thigh bone (femur) length and abdominal circumference. A computer generates an estimate of the baby's weight based on those findings.
Bear in mind that these are indeed estimates. Ultrasounds used to predict weight of the baby can be inaccurate by 10% or more. Be very cautious to schedule an induction or cesarean based on the findings of a "large" baby made exclusively on ultrasound measurements.
Potential Risks to Pregnancy Ultrasound
In the last 30 years, no conclusive evidence has shown that the levels of ultrasound used on humans are harmful. However some animal studies with higher levels of ultrasound have indicated changes in cell structure or function and even cell death. These studies seem to indicate that the tissue or body part that was being examined under the high frequency waves was altered in some way.
As a result the NIH has released the following statement:
“Ultrasound examination in pregnancy should be performed for a specific medical indication.”
Perhaps one of the biggest risks of ultrasound is the chance of identifying something “outside the normal range” with the baby and the inevitable invasive tests, such as amniocentesis that result. More often than not, these “unusual” findings either resolve on their own or turn out to be normal by the time the baby is born. As with any other prenatal test, be sure that you have a very good reason for getting an ultrasound.
Brenda Lane - Brenda Lane is a published author, Lamaze certified childbirth educator, DONA certified birth doula and approved birth doula trainer.
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