An obstetric ultrasound, also known as prenatal ultrasound, is typically performed before 13 weeks and 6 days (first trimester) of pregnancy. This is done to confirm the pregnancy. If you suffer from pelvic pain or vaginal bleeding during this time, the ultrasound can check if
- You have developed pregnancy outside the uterus, such as the fallopian tube (ectopic pregnancy)
- The heart activity of the baby is okay
- There has been as abortion
- If you have any abnormal growths, such as fibroids in your uterus
The next ultrasound is routinely done for all women in the 20th (second trimester) week of pregnancy. This is to check
- If the baby has any anatomical (physical) defect
- The baby’s weight
- The baby’s heart rate
- The amount of amniotic fluid in the uterus
- The status of your cervix (whether it is incompetent or has shortened early)
- The progression of uterine fibroids or ovarian cysts, if any
- If you have multiple pregnancies (twins, triplets, or more)
- The sex of the baby (only if you wish to know)
The due date is calculated from the last date of your periods. If you do not remember the last date of your periods, the doctor can perform an ultrasound any time before the 20th week to determine your due date.
The doctor can perform an obstetric anytime during the pregnancy when they need to monitor your pregnancy and the health of the baby or observe the effect of ongoing treatment for any of your conditions, such as polyhydramnios (excessive amniotic fluid in the uterus).
What is done before the obstetric ultrasound?
There are no special precautions that you need to take before coming for the ultrasound. You might be asked to drink water up to six glasses or until you feel like peeing. You would not be allowed to go to the washroom before you get your ultrasound done. Your full bladder helps the doctor to visualize your baby more clearly.
How is an obstetric ultrasound performed?
You will be asked to rest on your back.
Next, the doctor will move a small device (called a transducer) over your abdomen while applying a little pressure. They can also use a tubular probe into your vagina that functions similar to the transducer.
You may be asked to hold your breaths several times during the procedure.
The transducer emits high-frequency sound waves to the internal structures, including your uterus, its surrounding organs/structures, and your baby. These sound waves are reflected and captured by the transducer. The transducer then displays the captured waves onto the screen in the form of white and black images. Your doctor can help you see your baby in the images.
Getting an obstetric ultrasound is a very simple, safe, and painless test that takes around 30 minutes. You will only feel minimal discomfort due to the pressure of the transducer on your abdomen.
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Pregnancy: Prenatal Ultrasonography. Available at: https://my.clevelandclinic.org/health/diagnostics/9704-pregnancy-prenatal-ultrasonography/