A prenatal ultrasound (also called a sonogram) is a non-invasive diagnostic test that uses sound waves to create a visual image of your baby, the placenta and uterus, and other pelvic organs. It enables your doctor to collect valuable information about the progress of your pregnancy and the health of your baby .
During the exam, an ultrasound technician (sonographer) sends high- frequency sound waves through your uterus, which bounce off your baby. A computer then translates the echo sounds into video images that show your baby’s shape, position and movements. (Ultrasonic waves are also used in the handheld device called a Doppler.which your doctor uses during your prenatal visits to listen to your baby ‘s heartbeat ).
You may have an early ultrasound at your doctor’s office at 6 to 10 weeks to confirm and date the pregnancy. Or you can have an ultrasound after the standard mid-pregnancy ultrasound, between 18 and 22 weeks . During this time , you can find out the gender of your baby if you wish. (The technician will likely give you a grainy printout of the sonogram as a souvenir) .You may also have a sonogram performed as part of a genetic evaluation, such as a nuchal translucency test, a chorionic villus sampling, or an amniocentesis, or at any other time when there are signs of a problem with your baby. You will have more frequent ultrasounds if you have diabetes, high blood pressure, or other medical complications.
What information will my mid-pregnancy ultrasound provide?
For a typical mid-pregnancy sonogram, your doctor will use a sonograph to perform an ultrasound scan of:
Check your baby’s heartbeat
To make sure the heartbeat is normal , your healthcare provider will measure the number of beats per minute.
Measure your baby’s height
The sonographer will measure your baby across the skull, along the femur, and around the abdomen to make sure they are about the appropriate size for their age.If this is your first ultrasound and your baby is more than two weeks older or shorter than they should be, chances are your due date has been rescheduled and you will be rescheduled.If your doctor has concerns about how your baby is growing, he or she will order one or more follow-up ultrasounds to check your baby’s progress.
Check if there is more than one baby
By now you’ll probably know if you ‘re carrying twins or a higher multiple. Most women pregnant with multiples measure large in the first trimester and have an ultrasound done at that time to confirm the number of babies .
Check the position of the placenta
When the placenta covers the cervix (placenta previa), bleeding can occur later in the pregnancy. If your doctor diagnoses this condition, she or he will most likely order a follow-up exam early in the third trimester to determine if the placenta is still covering the cervix. In the meantime: don’t panic!Only a small percentage of placenta previas found on ultrasound before 20 weeks will still pose a problem when the baby is due.
Estimate the amount of amniotic fluid in the uterus
If the sonogram shows you have too much or too little amniotic fluid, there could be a problem. You will have a full exam to see if the cause can be identife, and your doctor may want to monitor you with regular ultrasound scans .
Check the baby for physical abnormalities
Your doctor will take a close look at your baby’s basic anatomy , including the head, neck, chest, heart, spine, abdomen, kidneys, bladder, arms, legs, and umbilical cord to make sure they are developing properly. If you got a suspicious result on a multiple marker or first trimester screening test, or if there is any other cause for concern, the technician will perform a more thorough scan (Stage II) to look for signs of a birth defect or Down syndrome .
Try to determine the sex of your baby
If you want to find out if your baby is a boy or a girl, you can usually do this at the mid-pregnancy (16 to 20 weeks) ultrasound , unless covering your child’s hand during the examination his genitals.In some cases, it’s important for your doctor to know your baby’s sex — for example, if the baby is thought to be at risk for certain congenital conditions.
Let your doctor know if you don’t want to know your baby’s sex so it doesn’t spoil the surprise during the test.