Week 18 Ultrasound: What It Would Look Like

Halfway through your pregnancy, typically between weeks 18 and 20, your health care provider might recommend a detailed ultrasound examination to check your unborn baby's development. For many women, this is the first and only ultrasound they will receive during their pregnancy.

At 18 weeks, your baby-to-be is large enough that your sonographer will perform the ultrasound transabdominally. With a transabdominal exam, the sonographer will first place gel on your abdomen so that the transducer can slide more easily over your tummy. The transducer is a radio soundwave-emitting device that helps produce an image of your baby in utero that the sonographer then uses to evaluate your baby's health.

What Your Sonographer Looks For During Your Exam:

• Fetal measurements of the head, abdomen, and femur. If this is your first ultrasound, these measurements help determine or confirm your unborn baby's age. With a follow-up ultrasound, these measurements are used to assess how well the baby is growing.
• Fetal heart rate and rhythm. The sonographer charts your baby-to-be's heart rate to make sure it falls into the normal range of between 120-160 beats per minute.
• Fetal head, chest, and abdomen. Each of these structures is evaluated to make sure they are not only in the right location but also that they are functioning normally.
• Fetal face. The sonographer will take a close look at the unborn baby's face to check for signs of cleft lip and/or palate.
• Fetal spine. By evaluating the baby's spine, the sonographer can rule out neural tube defects.
• Fetal extremities examined. Your unborn baby's arms, legs, hands, and feet will get the once-over to ensure they are developing well and working properly.
• Placenta appearance and location evaluated. The sonographer will also check the placenta to make sure it appears healthy and that it's in the right position.
• Amniotic fluid is assessed. Too much or too little amniotic fluid might signal a problem with your unborn baby's development.
• Uterus and surrounding areas. Besides evaluating the mother-to-be for fibroids, ovarian cysts, or other pelvic conditions, the sonographer will also confirm that the cervix is closed.
• Gender determination. Figuring out your unborn baby's sex isn't really part of the ultrasound, even though for most parents that's the most memorable moment during the exam. Your sonographer might or might not be able to tell if your baby is a boy or girl. Depending on how much your baby moves and what position he or she takes, the sonographer might be able to get a look at your baby's sex.

Terms to Know

Placenta previa: Implantation of the placenta in the lower portion of the uterus, covering part of the cervix. Placenta previa can result in bleeding during pregnancy and could affect the method of delivering the baby.

Neural tube defects (NTD): Abnormalities of the spine, such as spina bifida, and related abnormalities of the fetal brain.

Important Information About Your Pregnancy

• Learn more about your baby in the second trimester.
• Discover more about your 18th week of pregnancy.
• Read about your previous week of pregnancy.

Images courtesy of the American Institute of Ultrasound in Medicine (AIUM.org).