Prenatal ultrasound

Reasons for prenatal ultrasound 

• To confirm (make sure) you’re pregnant
• To check your baby’s age and growth. This helps your provider figure out your due date. 
• To check your baby’s heartbeat, muscle tone, movement and overall development
• To check to see if you’re pregnant with twins, triplets or more (also called multiples)
• To screen for birth defects, like spina bifida or heart defects. Screening means seeing if your baby is more likely than others to have a health condition; it doesn’t mean finding out for sure if your baby has the condition. After an ultrasound, your provider may want to do more tests, called diagnostic tests, to see for sure if your baby has a birth defect. Birth defects are health conditions that a baby has at birth. Birth defects change the shape or function of one or more parts of the body. They can cause problems in overall health, in how the body develops, or in how the body works.
• To help with other prenatal tests, like chorionic villus sampling
• To examine your ovaries and uterus (womb). Ovaries are where eggs are stored in your body.
• To check for pregnancy complications, including ectopic pregnancy, molar pregnancyand miscarriage.

First trimester

• In the first trimester, a standard ultrasound examination typically includes:
• Gestational sac size, location, and number
• Identification of the embryo and/or yolk sac
• Measurement of fetal length (known as the crown-rump length)
• Fetal number, including number of amnionic sacs and chorionic sacs for multiple gestations
• Embryonic/fetal cardiac activity
• Assessment of embryonic/fetal anatomy appropriate for the first trimester
• Evaluation of the maternal uterus, tubes, ovaries, and surrounding structures
• Evaluation of the fetal nuchal fold, with consideration of fetal nuchal translucency assessment

Second and third trimester

• In the second trimester, a standard ultrasound exam typically includes:
• Fetal number, including number of amnionic sacs and chorionic sacs for multiple gestations
• Fetal cardiac activity
• Fetal position relative to the uterus and cervix
• Location and appearance of the placenta, including site of umbilical cord insertion when possible
• Amnionic fluid volume
• Gestational age assessment
• Fetal weight estimation
• Fetal anatomical survey
• Evaluation of the maternal uterus, tubes, ovaries, and surrounding structures when appropriate

How to prepare for an ultrasound

During an ultrasound earlier in the pregnancy, you may need to have a full bladder for the technician to get a clear image of the fetus and your reproductive organs. You should drink two to three eight-ounce glasses of water one hour before your scheduled ultrasound. You shouldn’t urinate before your ultrasound so you arrive at your appointment with a full bladder.

What happens during an ultrasound

During an ultrasound, you lie down on an examination table or bed. An ultrasound technician applies a special gel to your abdomen and pelvic area. The gel is water-based, so it shouldn’t leave marks on your clothes or skin. The gel helps the sound waves travel properly.

Next, the technician places a small wand, called a transducer, onto your belly. They move the transducer to capture black and white images onto the ultrasound screen. The technician may also take measurements of the image on the screen. They may ask you to move or hold your breath while they capture images.

The technician then checks to see if the necessary images were captured and if they are clear. Then, the technician wipes off the gel and you can empty your bladder.