Grainy images from a prenatal sonogram are often baby's first picture for the baby book. This procedure has become commonplace in modern obstetrical care, with many low risk mothers receiving two or more ultrasounds during pregnancy and high-risk mothers receiving many more.
About the Procedure
Ultrasound sonography is a straightforward procedure for the mother. In the first few weeks of a pregnancy, the procedure will be done transvaginally instead of abdominally. A handheld transducer is inserted into the vaginal canal and images are shown on a screen. This is often done with a full bladder to better enhance the clarity of the images and for some newly pregnant mothers it can be a bit uncomfortable.
Late in the first trimester, abdominal ultrasound is possible. The sonography technician will use a lubricating gel to help with the transmission of the sound waves. This procedure is rarely uncomfortable.
In both cases, the transducer produces ultrasonic (high frequency) sound waves that bounce off the mother and baby's tissues, producing an echo. The transmitter then records and interprets the echoes to produce the image on the screen.
First Trimester Uses
In the first trimester, ultrasound may be used to confirm a pregnancy, check for a heartbeat, look for multiple gestations or establish an estimated date of delivery. Early in the pregnancy, the age of the embryo is accurate within about 10 days and the procedure can show a beating heart as early as seven or eight weeks. If you are considered low risk in your pregnancy and are sure of the date of your last menstrual period, you may not need an ultrasound at this or any other point in your pregnancy.
Second Trimester Uses
In the second trimester, ultrasound technology can detect certain abnormalities in the growing fetus. Heart, gastrointestinal, kidney and some neurological problems (such as spina bifida) can be identified early on. This can allow your care providers to develop a treatment plan and to evaluate your risks of not carrying the pregnancy to term.
A non-invasive screening for chromosomal abnormalities is usually performed at the end of the first or the beginning of the second trimester. This scan measures the folds of skin on the neck and checks for extra fluid that could indicate a problem. While this scan is not diagnostic of a chromosomal abnormality, it can identify when further testing is needed.
Third Trimester Uses
Late in the pregnancy, you might have an ultrasound performed to evaluate the position of the baby (if your care provider cannot determine this by manual palpitation), to assess the condition of the placenta if you are considered post-dates, to check the location of the placenta if you have had spotting, or as part of a stress test or non-stress test.
Risks and Side Effects
The general consensus is that ultrasound scans are safe for both mother and baby. However, ultrasound waves have the potential to raise the core temperate of a developing fetus, especially in extended use or high definition situations. This raised core temperature can hinder development through the loss of functional ability of certain enzymes. Because of this, qualified medical professionals should only perform sonograms when the medical benefit outweighs the potential risks.
References
- "The Complete Book of Pregnancy and Childbirth"; Kitzinger, Sheila; November 1997
- Ultrasound: Sonogram; American Pregnancy Association
- "Questions about Prenatal Ultrasound and the Alarming Increase in Autism"; Rodgers, Caroline; Midwifery Today; Issue 80, Winter 2006.
