TLDR: The 12-week ultrasound is an exciting milestone in your pregnancy. You get to see your developing baby…and confirm that there’s only one in there. But having questions about what to expect during this appointment is normal. We asked a doctor of maternal-fetal medicine to tell us everything expecting parents should know about the 12-week scan, including what markers your doctor is looking for in a healthy pregnancy.
I had no idea what to expect when it came to my 12-week ultrasound.
Even though I was excited to finally see an image of my daughter, I was also afraid of the possibility of finding out something might be wrong with her. So, on the day of the scan, I found myself sitting in the waiting room trying my best to occupy myself with magazines, social media, or anything else I could get my hands on.
Finally, my husband and I were called back and the ultrasound started. Within seconds, we saw our baby girl on the screen. As I had anticipated, she was the most beautiful thing I had ever laid my eyes on.
However, as I sat there, I couldn’t help but wonder what they were looking for and whether or not I was going to find out the results that day.
Fifteen minutes later, the ultrasound was finished and my husband and I were relieved to hear that our daughter was 100% healthy.
Even though I was happy with my results, I couldn’t help but wonder why we have a scan at this point in pregnancy, whether or not it’s safe, and what the indicators of a healthy baby are. I talked with Dr. Camille Hoffman1 , a maternal-fetal medicine physician at the University of Colorado who focuses on the management of women with high-risk pregnancies, to find out everything there is to know about the 12-week ultrasound.
What is the 12-week ultrasound?
Dr. Camille Hoffman: The 12-week ultrasound usually occurs between 11 and 13 weeks. What we look for during the ultrasound is how many fetuses there are and if there’s any evidence of early predictors of a chromosome problem or a birth defect, which we call anatomic abnormalities. In general, we look for signs that pregnancy is off to a good start or potentially not off to a good start.
What should you expect during this ultrasound?
CH: You can expect to have an ultrasound across the abdomen. Since the fetus is now big enough, the ultrasound can be done through the mom’s belly rather than transvaginally as she may have done earlier on in her pregnancy.
What is the 12-week ultrasound looking for?
CH: Initially, we look to see where and how the placenta is forming, if there’s a normal amount of amniotic fluid, and how the fetus looks. We look at the major features in the brain, the heartbeat, and the skeleton, and we see if there are two arms, and two legs, and if the umbilical cord is going into the future belly button.
However, the main thing that we do during this ultrasound that can’t be done during other times in pregnancy is what’s called a measurement of the nuchal translucency2 , also known as NT. NT is a little sliver of fluid at the back of the baby's neck in between the spine and the skin. If that area is enlarged, which is uncommon, but it can be predictive of a chromosome problem, a small genetic problem, or some kind of anatomic problem.
What are the indicators of a healthy pregnancy?
CH: The indicators of a healthy pregnancy are normal-looking amniotic fluid, a placenta that’s forming in a good location, and a fetus that measures according to what you think the due date is. Also, two arms, two legs, a normal-looking skull and spine, as well as a good measurement of the nuchal translucency. Those are all indicators that things so far are going just fine.
Why can it be done between 11 to 13 weeks?
CH: It's actually based on the measurement of the crown-rump length–the measurement of a fetus from the crown of its head to its bottom “rump” area. These scales were developed to determine what the norms were for that nuchal translucency measurement. So this is all based on a crown-rump length of 45 to 84 millimeters, which usually translates to a pregnancy that's about 11 weeks 0 days to 12 weeks 6 days.
When do you find out the results?
CH: You find out the results right away. The maternal-fetal medicine physician, obstetrician, or whoever was doing the ultrasound at that time will come in and discuss the results with you.
Is the 12-week ultrasound safe for the fetus?
CH: All ultrasound machines use what we call the ALARA Principle: “As low as reasonably achievable.” This means that every ultrasound is set to not go above certain thresholds, ensuring that a fetus will not be exposed to an excessive amount of ultrasound waves.
For example, in cases where they use ultrasound to deteriorate fibroids, the probes are set to a much higher frequency and require a lot of time spent over a certain area that doesn't move in order to actually deteriorate the fibroids. So, when you think of a little fetus that's moving around…not only is the frequency not high enough to harm your baby, but you couldn't even stay over the same area because the fetus is constantly shifting. So yes, ultrasounds are safe for you and your baby.