12 Week Ultrasound: What to Expect & Why it’s Important

As you enter the final stretch of your first trimester, your anticipation for the 12-week ultrasound grows. Amidst the fun early pregnancy symptoms and unique cravings, this ultrasound holds significant importance. It not only provides the first opportunity for many women to see the beginnings of their precious newborns, but it also serves as a crucial milestone in confirming a healthy pregnancy and setting the stage for the exciting journey ahead.

In this comprehensive guide, we will walk you through what you can expect during your 12-week ultrasound.

12 Week Ultrasound: What It’s For

Unless you’ve already had an early pregnancy ultrasound (aka typically a 6-week ultrasound — reserved for high-risk pregnancies), your OB will recommend your first ultrasound at the end of the first trimester, around the 12-week mark.

Your 12-week ultrasound equips you with essential information about your pregnancy and developing child. Also known as a dating scan, this ultrasound has four main objectives:

• Establish your estimated due date
• Check if you have one or more buns in the oven
• Test for genetic or chromosomal abnormality, like Down Syndrome
• Verify your baby is developing normally

In addition to confirming your pregnancy is moving along smoothly, you’ll also catch the first glimpse of your baby-to-be. The sonogram of your baby (the image produced by your ultrasound) will be a little rough around the edges but seeing the earliest inklings of your child is a moving experience nonetheless.

12 Week Ultrasound: How It Works

In general, an ultrasound works by using sonic frequencies (or sound waves) to examine the goings-on inside your uterus. At 12 weeks, the ultrasound tech will glide the ultrasound wand (also known as the transducer) over your abdomen so that sonic frequencies can bounce off your internal organs, fluids, and baby to create a picture of the inside of your body.

Remember, the resulting sonogram is not a photograph. Rather, it’s a translation of the data obtained by the transducer—an estimation of the distance between its sound waves and your baby’s body.

Here’s how an ultrasound identifies the first batch of information about your baby.

Due Date

Until your first ultrasound, your doctor and our pregnancy calculator can only date your pregnancy by using one of the following:

• The date of your last menstrual period
• Your date of conception
• Your IVF transfer date

However, during your 12-week ultrasound, your sonographer can measure the size of your baby’s skull, abdominal circumference, and femur length to get a more refined estimate of when your pregnancy began and when you can expect to say Happy Birthday to your little man.

Multiples

If you’re carrying twins, your sonographer will be able to see two distinct fetuses cocooned in your womb. Should a duo make an appearance on your sonogram, the next step is to identify which of the two types of twins they are:

• Dichorionic twins – Dichorionic twins are nourished by separate placentas. Most dichorionic twins are fraternal, though it is possible (albeit rare) to give birth to identical dichorionic twins. Dichorionic twins are the simpler type of twins to be pregnant with because they’re growing independently—the fetal version of getting your own bedroom!
• Monochorionic twins – Monochorionic twins are always identical, and they share the same placenta in your uterus. If you’re pregnant with identical twins, the next step is to assess if they’re also monoamniotic—both cozying up in the same amniotic sac. Mo/mo pregnancies are more vulnerable to complications, so in this situation, you may feel most comfortable finding a new OB who specializes in this specific kind of prenatal health.

Genetic Screening

To screen for genetic disorders, your obstetrician will use a nuchal translucency test as a risk assessment. This test does not diagnose but rather estimates the likelihood that your baby will have one of three chromosomal disorders:

• Down syndrome, when a baby is born with an extra 21st chromosome, leading to cognitive challenges and potential issues with digestion, heart function, or other organs.
• Trisomy 13 or Trisomy 18, wherein a baby is born with an extra 13th or 18th chromosome (respectively), which can lead to more severe intellectual inhibition, birth defects, or compromised organ function.

The nuchal translucency test includes data derived from your ultrasound, some bloodwork, and an analysis of the amount of fluid at the nape of your baby’s neck.

While these tests can be one of the most nerve-wracking segments of your ultrasound, remember that these early screenings can’t definitively ascertain the health of your child. Rather, they’re a tool to help you prepare for a potential chromosome abnormality so that you can take care of yourself and your little one along the way.

Fetal Development At 12 Weeks

At 12 weeks into pregnancy, your baby is approximately two inches long. Despite the tiny size, your doctor will be able to scan your baby to make sure all major organs have developed properly such as their:

• Skeleton: The fetus’s skeleton is initially formed from cartilage at 12 weeks, gradually hardening into bone over the following weeks.
• Intestines: Rapid organ development occurs at 12 weeks. The intestines, previously growing rapidly and protruding into the umbilical cord, now regress into the abdomen.
• Movement: As they move, their wrists and elbows bend. The eyelids, although still fused shut, have shifted from the side of the head to the final position at the front.
• Reflexes: Starting at 12 weeks, your little one begins practicing reflexes. These include clenching the eye muscles, making sucking actions with the mouth, and bending fingers and toes.

The Declined Risk of Miscarriage

For any expectant parent, the initial trimester is a time filled with a blend of anticipation and anxiety. The fear of pregnancy loss is a valid concern that often occupies the minds of pregnant women. We want to assure you that the risk of miscarriage significantly decreases as you reach the 12-week mark. In fact, it drops from about 80% in the first trimester to just 1.7% at week 12.

Common Questions About 12 Week Ultrasounds

Whatever emotions you (with a little boost from your hormones) are feeling, it’s not uncommon to have some anxiety before this first ultrasound appointment. Let’s move through a few FAQs about your first ultrasound to alleviate any pre-appointment jitters you may be feeling.

Are ultrasounds safe for my baby and me?

Because no radiation is used in ultrasounds, the American College of Obstetricians and Gynecologists believes that ultrasounds are perfectly safe and will not adversely affect either your baby’s healthy gestation or your own prenatal well-being.

How many more ultrasounds do I need?

What weeks do you get ultrasounds during pregnancy: you should expect to have two ultrasounds during your pregnancy:

• First-trimester screening – The dating scan
• Second-trimester screening – The anatomy scan

If your obstetrician detects any potential complications, or if you have a high-risk pregnancy (as in the case of twins and mo/mo pregnancies), you may need to schedule an extra ultrasound to confirm your baby (or babies!) are developing healthily.

Will I learn the sex of my baby during this ultrasound?

While you may be anxious to learn whether you’re carrying a little he or she at 12 weeks, ultrasounds can’t accurately make that assessment at this stage of your pregnancy.

Proponents of a method called the Nub Theory claim that by 12 weeks, the caudal notch—the earliest form of the genitals’ taking shape—is differentiated enough between boys and girls to make a guess at gender. The theory works like this:

• If your baby is a boy, the caudal notch will be angled upwards by at least 30 degrees.
• If your baby is a girl, her caudal notch will be angled downwards at around 10 degrees.

While you can ask your sonographer about the angle of the caudal notch on your sonogram, a study found that this method of gender identification is only 70% accurate at this early stage of pregnancy, explaining why gender is typically identified during the anatomy scan ultrasound, which takes place between 18 and 20 weeks.

There is also the Skull Theory, an alleged sex-prediction test that claims to predict a baby’s sex at 12 weeks, just from a routine early ultrasound photo. It suggests that a rounded skull indicates a baby girl, while a more angular or squared-off skull suggests a baby boy. Although the skull theory lacks scientific proof, many parents enjoy using it as a playful way to speculate about their baby’s sex.

How do ultrasounds determine sex during the anatomy scan?

By 18 to 20 weeks, your fetus’ reproductive organs will be further along in their development. If you’re carrying a boy, he’ll exhibit a scrotum, testicles, and a penis.

If you’re carrying a girl, your sonographer will look for a labia and clitoris.

To Beat Your Ultrasound To The Punch, Take A SneakPeek

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Sources:

1. National Institutes of Health. Ultrasound. https://www.nibib.nih.gov/science-education/science-topics/ultrasound
2. The American College of Obstetricians and Gynecologists. Methods for Estimating The Due Date. https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2017/05/methods-for-estimating-the-due-date
3. The New York Times. When and Why to Get Ultrasounds During Pregnancy. https://www.nytimes.com/article/pregnancy-ultrasounds-guide.html
4. Healthline. Mo/Mo Twins: Definition, Risks, and More. https://www.healthline.com/health/pregnancy/momo-twins#diagnosis
5. John Hopkins Medicine. Combined First-Trimester Nuchal Translucency Screening. https://www.hopkinsmedicine.org/gynecology_obstetrics/specialty_areas/maternal_fetal_medicine/services/fetal_diagnostic_procedures/first_trimester_nuchal_translucency_screening.html
6. NCBI. First-trimester determination of fetal gender by ultrasound. https://pubmed.ncbi.nlm.nih.gov/10380292/
7. VeryWell Family. How to Tell a Baby’s Gender on the Ultrasound. https://www.verywellfamily.com/ultrasound-photos-of-girls-and-boys-in-pregnancy-2758367
8. Grow by WebMD. Slideshow: Fetal Development Month by Month. ??https://www.webmd.com/baby/ss/slideshow-fetal-development
9. NCT (National Childbirth Trust). Miscarriage: Your questions answered. https://www.nct.org.uk/pregnancy/miscarriage/miscarriage-your-questions-answered
10. American Pregnancy Association. 12 Weeks Pregnant. https://americanpregnancy.org/healthy-pregnancy/week-by-week/12-weeks-pregnant/
11. Netmums. The Skull Theory. https://www.netmums.com/pregnancy/skull-theory