Being pregnant for the first time is entirely new territory for most – if it feels daunting, you’re not alone! Use our full series on Routine Ultrasounds in Pregnancy as your guide during these next 9(ish) months.
Your First Trimester: The 10 Week Ultrasound
There is nothing sweeter than hearing your baby’s heartbeat for the first time, and at your first pregnancy ultrasound, that’s just what you’ll get to do!
At 10 weeks of pregnancy, you are already more than halfway through your first trimester and already in your third month. You may have been surprised to find out your doctor’s office doesn’t schedule the first routine prenatal visit until around this time. That’s a long time to wait to see your baby, especially since most women find out they are pregnant on an at-home test weeks prior. Worry not, that baby will be worth the wait!
Based on certain risk factors, your doctor may also recommend a Viability Check Ultrasound in early pregnancy, usually around 6-8 weeks.
How does an ultrasound work, anyway?
Ultrasound technology uses sound waves to create an image of structures inside the body. During a transvaginal ultrasound, something called a transducer is inserted into your vaginal canal, where it emits sound waves that bounce of structures in your pelvis and projects a real-time image onto a screen. This image is called a sonogram.
You can expect that both you and your provider or ultrasound tech will have a view of what’s going on on the sonogram. Still images are usually also captured so that they can be viewed later.
Don’t worry, ultrasounds are considered very safe for both you and your baby, and your baby will be none the wiser that you are spying on him or her!
How is gestational age calculated?
Gestational age and due date are calculated based on the first day of your last menstrual period. There are many helpful apps and online calculators that can do the math for you. If you have an irregular period or are unsure of your last period, your doctor will assign your due date based on measurements done with the ultrasound. To do this, your doctor (or ultrasound technician) will measure the length of your baby’s body from ‘crown to rump.’ The crown-rump length (CRL) is the number of millimeters or centimeters from the top of the baby’s head (crown) to the bottom of their buttocks (rump). Fun fact: all the way throughout your pregnancy, the CRL is usually about the same as the length of the umbilical cord!
If there is a large discrepancy between the first day of your last period and the measurements your doctor is getting on the ultrasound, he or she will likely consider the ultrasound as more accurate and assign a due date that way.
In later ultrasounds, and once your baby has developed beyond 14 weeks, the fetus will be large enough for additional measurements such as head circumference and femur length. (Link to Anatomy Scan ultrasound)
Your baby at 10 weeks
At 10 weeks, the embryo is still small – between 1 and 2 inches long and a little over an ounce in weight. He or she is about the size of a small lime or a large strawberry!
After week 10, your baby is graduating from the embryonic period to the fetal period. By now, the vital organs are functioning, but they have a lot of maturing to do. Bones and cartilage are developing and hair and nails may become visible. Additionally, fingers are no longer webbed and the tail the embryo had in the first weeks is gone. Your baby is starting to look a lot more like a baby and a lot less like a tadpole!
The 10-week ultrasound
To get the most accurate images, this ultrasound will most likely be done transvaginally. This involves inserting a long, thin transducer, or wand, into your vaginal canal to produce pictures of your uterus and fetus. While you might feel some pressure when the wand is moved, you should not experience pain.
At some point during the ultrasound, you can expect to listen to your baby’s heartbeat. A normal fetal heart rate is between 120 and 160 beats per minute (much faster than ours!). You may want to get your phone out for this part and record these first sounds of cardiac activity – it will be music to your ears!
Another measurement your doctor or tech might perform is the ‘nuchal translucency test,’ which measures the thickness of the back of the fetus’ neck. Abnormal measurements can indicate Down Syndrome or other congenital abnormalities. Usually this test is paired with a blood test to confirm findings. Please keep in mind, tests such as these are optional, and you should never feel pressured to have them done if you don’t want to.
Besides the fetus, your provider or tech will be looking for a roundish pouch called a yolk sac. Earlier in pregnancy, the yolk sac is visible even before the fetus. By week 10, the yolk sac’s job of producing cells and delivering nutrients is done, and it will gradually get smaller and disappear (usually by week 14-20).
Do twins run in your family? While chances are low, you’ll also find out at this visit whether there is more than one baby in your belly. Since there is no way to detect twins prior to the first ultrasound, women who experience hearing this news often report it is truly one of the biggest shocks of their lifetime!
Either way, don’t forget to ask for printed or digital copies of those adorable first pictures of your baby.
What about the placenta?
You may have heard people talk about the placenta during pregnancy. The placenta is proof of just how amazing the female body is – it grows a whole new organ during pregnancy! That fatigue you’re experiencing is starting to make more sense, isn’t it? This organ attaches to your uterus and provides nutrients and oxygen to your baby via the umbilical cord throughout your pregnancy. At weeks 10-12, the placenta is getting ready to take over these functions from something called the corpus luteum. While it will continue to grow with your baby, right now it only weighs about 1-2 ounces, just like the fetus.
What else can you expect from this visit?
In addition to the ultrasound, you can expect to have your weight and vital signs measured, answer questions about medications you are currently taking and any allergies you may have, provide details about your (and your partner’s) familial genetic history, leave a urine sample, have blood drawn, and possibly get a pap smear and STD testing done. Your provider will also likely go over recommendations for nutrition and exercise during pregnancy. Most importantly, you should feel comfortable asking as many questions as possible during this visit – there are no dumb questions, and, trust me, your doctor or midwife has heard it all before.
Feeling nervous?
It is normal to have anxiety before the first ultrasound, especially if you’ve endured pregnancy loss in the past. Take some deeps breaths and lean on your partner, family, or friends for support. If you do end up finding out bad news at this ultrasound, be sure to talk to your provider about resources for emotional support and when it’s safe to start trying again.
What about the other ultrasounds?
Stay tuned for further articles with details on additional ultrasounds done in pregnancy, such as the Viability Check done around 6-8 weeks, the Anatomy Scan (done around 18-20 weeks), and the Third Trimester ultrasound to estimate fetal weight and positioning (done at 36-38 weeks).
Read More of Our Series on Ultrasound Scans
The Viability Check Ultrasound Scan
Routine blood tests during pregnancy: Our guide to the blood tests you’ll be recommended during pregnancy