What is an ultrasound?
An obstetric ultrasound is a diagnostic exam performed during pregnancy by a registered medical sonographer or doctor.
Also known as a sonogram, it uses high-frequency sound waves sent into the body through a transducer placed on the stomach. The sound waves are reflected off internal organs or structures inside the body and converted into an image on a screen or monitor.
Why am I having an ultrasound?
An ultrasound in the first trimester may be done to help your doctor diagnose and confirm pregnancy, determine gestational age, assess fetal size and development, locate the placenta, and determine any multiple fetuses. It will also identify abnormalities of the placenta or uterus and assess fetal heart activity. An early ultrasound may be used to identify potential causes of bleeding, determine the cause of unusual pain early in pregnancy, or to determine the presence of an ectopic pregnancy.
Scans during the second trimester also examine the placenta, evaluate fetal anatomy for abnormalities, check amount of amniotic fluid, measure the length of the cervix and monitor fetal growth.
Scans in the third trimester again monitor fetal growth and check the amniotic fluid, but also determine the position of the fetus.
Can an ultrasound detect all abnormalities?
Some types of abnormalities cannot be seen on an ultrasound because they are too small of not visible by ultrasound. The size and position of the fetus could also prevent abnormalities from being seen.
More than just finding ten fingers and toes however, the ultrasound performed around 18 weeks gestation evaluates of the anatomy of the baby:
- the size and shape of the head
- the structures within the brain
- the presence of a continuous spinal column (no spina bifida or neural tube defect)
- facial features (no cleft lip or cleft palate)
- the stomach (no blockage in the upper part of the intestine system)
- separation between the chest and abdomen (no diaphragmatic hernia)
- the presence of normal heart chambers (no enlarged heart, nor holes in the heart), and normal vessels coming out of the heart (no narrowing or rearrangement of the aorta or pulmonary artery)
- the kidneys and bladder
- the bones of the legs and arms, and the reassurance of their movement
- the gender
Is ultrasound safe?
There are no documented harmful effect on patients or their fetuses with the use of ultrasound.
How do I prepare for an ultrasound?
A full bladder is necessary for optimal imaging. You will be asked to empty your bladder an hour before your appointment and then to drink 32 oz. of water. You should not urinate until after the exam.