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What is prenatal ultrasound scanning?
Ultrasound scanning is a procedure using high-frequency sound waves to show a picture of your unborn baby. It also shows images of your uterus, amniotic sac, placenta and ovaries. A small device called a transducer sends sound waves into the body, which reflect off internal structures, including your baby. The sound waves, or echoes that reflect back, are received by the transducer and translated into a picture on a screen that can also be printed out.
When is ultrasound used in pregnancy?
During your prenatal visits, your doctor discusses recommendations for ultrasound testing. An ultrasound may be performed to confirm that the placenta is healthy and attached normally, and that the baby is growing properly in the uterus and not in an abnormal location, otherwise called an ectopic pregnancy. Ultrasounds help your health care provider determine the number of babies developing, the baby's expected weight, the baby's position and the expected due date. This is especially useful when a women's menstrual history is not consistent with the size of the growing uterus. Major anatomical abnormalities or birth defects such as Down syndrome can show up on an ultrasound. It may also used to guide the doctor during amniocentesis by determining the location of the fetus and placenta. Although ultrasound is often accurate in predicting the sex of a baby in the later stages of pregnancy, it is not a foolproof method to determine the gender of the baby.
How do I prepare for an ultrasound?
A full bladder may assist the imaging of the baby. You may be asked to drink a large quantity of water, up to six glasses and refrain from urinating an hour before the test. You'll be allowed to empty your bladder right after the test is completed. You will be asked to wear a gown for an ultrasound. In general, no other special preparations are needed. Routinely, the exam will take 15 to 20 minutes.
What happens during an ultrasound?
There are two main types of ultrasound scanning, one is abdominal and the other is vaginal. Both utilize the same principles of ultrasound but each has different specificities because of the different placements. In the abdominal ultrasound, the technician puts a jellylike substance on your abdomen. Then the transducer is placed on your abdomen and moved over your stomach to visualize different parts of your baby and uterus. The vaginal ultrasound is more often used early in the pregnancy.
A protective sheath is placed over the transducer, which is usually smaller than a standard speculum used in a Pap smear, and inserted into the vagina. The ultrasound procedure is painless. Only mild discomfort may be felt from some pressure of the transducer. The jelly-like substance may also be cold, but not painful.
Is ultrasound scanning safe?
There is no evidence that ultrasounds are harmful in any way for the mother or fetus. Research on possible risks continues, however.
Are there any drawbacks to having an ultrasound scan?
In low-risk pregnancies, ultrasounds are effective at ruling out possible problems, but not as effective in detecting them. A routine ultrasound does not detect all fetal structural defects. This depends on the skill and accreditation of the sonographer. Besides missing some birth defects, a routine ultrasound can occasionally suggest a birth defect when none exists. In low-risk women, there is a 0.1 percent chance that they will be told their baby has a birth defect when none exists, but follow-up exams usually clear the error.
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