Understanding Prenatal Ultrasounds
Ultrasounds are a standard part of routine prenatal care. It's a straightforward procedure that allows your health care provider to monitor your pregnancy and make sure all is well with the developing fetus. During a traditional scan, the sonographer will gently run a transducer over the abdomen to generate sonogram images of the baby. Another possibility is to have a transvaginal scan (TVS), where a probe is inserted into the vagina to capture the same images, though this type of exam is generally only performed early on in pregnancy.
The first trimester
If you experience bleeding or some other abnormality early on in pregnancy, you might have a TVS done, but otherwise the first scan that might be performed is a dating ultrasound. If you are unsure of the first day of your last your period, having this type of ultrasound will determine the gestation age of the fetus and give you a due date. Typically it will be performed between weeks 10 and 14. This is also the time a nuchal translucency (NT) ultrasound might be done. This screen is used to identify the risk a baby might have Down's syndrome. As the scan on its own only presents the likelihood of Down's, an accurate assessment will require further diagnostic testing.
The second trimester
In Canada, most women's first ultrasound is usually scheduled between weeks 18 to 22 of a normal pregnancy. At this stage you will see a much clearer image of your child than you would in an earlier scan. Several health checks are done from this ultrasound. They include the following:
- the due date if it hasn't already been determined
- if the baby's size is right for the gestational age
- if you are carrying multiples
- gender determination, at your request
- proper organ development, including the heart, brain and kidneys
- a check on the placenta, umbilical cord and amniotic fluid
- uterine health
For some women, the second trimester scan will be the only ultrasound performed, but depending on your pregnancy, your health care provider may request an ultrasound at other times during the pregnancy. If you are considered high risk, had complications in previous pregnancies or are carrying multiples, you will likely have more scans than average performed. During the scans, development of the baby will continue to be monitored as well as any specific concerns identified by your physician or midwife. After 37 weeks, an ultrasound may be performed if it's suspected the baby is in a breech position. Some expectant parents choose to purchase 3-D photos and videos from a non-diagnostic prenatal image company. While having a 3-D photo of your baby is a great keepsake, this type of ultrasound should never be substituted for proper prenatal medical care.