A Special Look at First Trimester Ultrasound Pictures

Weeks 1 and 2 of Pregnancy

There's no ultrasound image of your baby-to-be for weeks 1 and 2 of pregnancy. While your health care provider counts these two weeks toward your due date, you aren't actually pregnant yet (assuming you're having a 40 week gestation; factors such as in vitro fertilization might affect this definition).

Confused? Understandable. Your estimated due date (EDD) is calculated using the first day of your last menstrual period (LMP). You weren't pregnant at that time, but it's the best reference your health care provider has for estimating your baby's potential arrival day (until you get an ultrasound, which may provide a more accurate due date).

3 Week Ultrasound

Embryonic Size: Not measurable

Embryonic Development Milestones: Fertilization

What You're Seeing: This week is when your pregnancy really begins. At some point, the sperm joins with the egg as it makes its way through the fallopian tube and to the uterus. Once together, the cells begin to divide rapidly so that next week, a sonographer may be able to capture baby-to-be's beginnings during an ultrasound examination.

4 Week Ultrasound

Embryonic Size: Not measurable

Embryonic Development Milestones: Positive pregnancy test

What You're Seeing: The small circle at the center of the sonogram may not look like much, but that little sac is a kind of baby cocoon called a gestational sac. The cells that make up this sac will begin to specialize.

Some cells will become part of the placenta. Some will form the amniotic sac that will fill with fluid to cushion your developing baby. Other cells are destined to form everything from delicate eyelashes to muscles and skin. But that's still a long way away.

5 Week Ultrasound

Embryonic Size: 1/18 to 1/16th of an inch in length (about the size of the pen dot)

Embryonic Development Milestones: Cells that will form the heart and the central nervous system are developing.

What You're Seeing: The dark area is the fluid filling the gestational sac. Eventually, this fluid will be replaced by a sac containing the amniotic fluid your baby will live in for the next few months.

The white circle within the fluid is called the yolk sac. Before the placenta is fully formed, the yolk sac plays a role in providing all the nutrients your baby needs to grow. Adjacent to the yolk sac, little "+" marks show a very early embryo.

The sonographer measures the length of the embryo (the crown-rump length or CRL) to confirm or revise the due date estimated from your LMP, or to evaluate the embryo's growth.

6 Week 3D Ultrasound

Embryonic Size: 1/6 to 1/4 of an inch in length

Embryonic Development Milestones: The embryo takes on a tucked C-shape. Head, legs, and umbilical cord are forming. Blood is pumping through what will become the heart.

What You're Seeing: In this 3D image of the developing embryo, you can see a big change since the previous week. The embryo curves inward, with the umbilical cord in the middle. The head appears at the upper right side of the image. Small buds can be seen where the arms and legs will eventually develop.

Also note that these images are derived from transvaginal ultrasounds. If someone gets a transabdominal ultrasound before week 7-8, oftentimes the resolution is too poor to see anything.

6 Week Ultrasound: Cardiac Activity

Embryonic Size: 1/6 to 1/4 of an inch in length

Embryonic Development Milestones: There is measurable embryonic cardiac activity.

What You're Seeing: Before the chambers of the heart are fully developed and a true fetal heartbeat can be detected (around 17–20 weeks of gestation), a sonographer will be able to pick up the electrical pulses that characterize early cardiac activity (though you'll still likely hear it referred to as a "heartbeat").

Here, the sonographer demonstrates the embryo's cardiac activity. The top part of the image shows the placement of a measuring tool on the ultrasound machine called an M-mode through the image of cardiac cells. This tool shows movement over time, which is displayed on the bottom part of the image. The image on the bottom shows how the embyro's "heart rate" is calculated.

7 Week Ultrasound

Embryonic Size: 1/4 to 1/3 of an inch in length (about the length of your pinkie fingernail)

Embryonic Development Milestones: The head is growing larger, and structures that will form the brain can be identified. Nostrils and lenses of the eyes develop.

What You're Seeing: During this week of the first trimester, you can see the embryo is developing in a bubble within the gestational sac. The bubble around the embryo is the amniotic cavity filled with amniotic fluid.

This liquid environment gives your baby room to grow, develop, and move. The amniotic fluid also cushions them from any external pressure on the abdomen. The black area inside the head is part of the developing neural tube.

8 Week Ultrasound

Embryonic Size: 0.6 inches in length and 0.04 ounces in weight

Embryonic Development Milestones: Your baby's hands and feet are developing. Fingers are beginning to form, but are still fused together. Elbows and ears are taking shape. The torso, arms, and legs are getting longer. You can see small, jerky movements on sonogram.

What You're Seeing: In this image, the embryo is lying on their back with their head to the right of the screen. In this now familiar c-shape, you can see that the head is becoming larger to accommodate their growing brain. The brain is divided into three main parts: the forebrain, the midbrain, and the hindbrain. As in the previous week, the hindbrain may be seen as a dark area in the back of the embryo's head.

9 Week Ultrasound

Embryonic Size: Almost 3/4 of an inch in length and 2 grams in weight

Embryonic Development Milestones: Facial features like eyelids and ears continue to develop.

What You're Seeing: The embryo appears at the bottom of the image with the head on the left. The arms and legs aren't seen from this angle, but the umbilical cord can be seen extending from the baby's abdomen on its way to the placenta.

The sonographer has marked the embryo's crown-rump length (CRL), which will help to confirm or revise the due date estimated from the LMP. Amniotic fluid (the dark area) surrounds the developing baby.

Week 9 Ultrasound: Fetal Interaction

Embryonic Size: Almost 3/4 of an inch in length and 2 grams in weight

Embryonic Development Milestones: The baby's forehead is large, and the chin is underdeveloped. The toes are fused together.

What You're Seeing: This image gives you a sneak peek at the interaction between the gestational parent's body and the embryo during the first trimester. The embryo is lying on its back with the head on the right side. The cells that will make up the heart are highlighted by the blue area.

The umbilical cord stretches from the developing baby's abdomen to the placenta, and the red and blue colors within the cord represent blood going to and from the placenta, where it picks up oxygen and nutrients.

10 Week Ultrasound

Embryonic Size: 1.22 inches in length and 0.14 ounces in weight

Embryonic Development Milestones: The eyelids are developing, and your baby's ears are fully formed (but not yet in position). The neck is forming. Fingers and toes are becoming more defined.

What You're Seeing: You'll notice in this image that the embryo is looking more and more like a newborn. Your arms and legs are visible, and a recognizable profile can be seen. The bright white areas in the profile are facial bones.

10 Week 3D Ultrasound

Embryonic Size: 1.22 inches in length and 0.14 ounces in weight

Embryonic Development Milestones: Rudimentary forms of all the organs are present, and cartilage is beginning to ossify and turn into bone. At the end of this week, your embryo becomes a fetus.

What You're Seeing: This 3D image gives an even clearer look at your baby. Notice that the embryo is still tucked into a c-shape, with the head toward the stomach and the arms and legs jutting outward. The umbilical cord is seen going from the baby's abdomen to the placenta.

11 Week Ultrasound

Fetal Size: 1.61 inches in length and 0.25 ounces in weight

Fetal Development Milestones: The chin and neck are developing. Facial features are becoming more defined. The ears move higher on the head.

What You're Seeing: Here the fetus is lying on its back with the head on the left side of the image and legs pointing up. From this image, you can see that the neck is growing, separating the large head from the rest of the body. The head still makes up more than 50% of the body size, which is normal. Facial bones are again seen as bright white areas in the profile.

11 Week 3D Ultrasound

Fetal Size: 1.61 inches in length and 0.25 ounces in weight

Fetal Development Milestones: Fingers and toes are now visible on an ultrasound. The genitalia is forming but not visible by ultrasound.

What You're Seeing: In this 3D picture, notice that the delicate facial features are more visible. Muscles and bones are building in the arms and legs. The baby has slung the umbilical cord over one shoulder. A close look also reveals tiny fingers and toes. If the image were live, you would be able to see the developing baby's jerky movements.

12 Week Ultrasound

Fetal Size: 2.13 inches crown to rump length and 0.49 ounces in weight

Fetal Development Milestones: Fingernails and toenails are beginning to form. Genitalia is continuing to develop as well, although it isn't visible on ultrasound. The kidneys are beginning to function. And the baby may be sucking their thumb!

What You're Seeing: With the baby in profile and the head on the right side, you can see that the facial profile is becoming more and more like what you'd expect to see in a newborn. They have one hand in front of their face as if they are shading their eyes.

13 Week Ultrasound

Fetal Size: Almost 3 inches crown to rump length and almost 1 ounce in weight

Fetal Development Milestones: The kidney and urinary tract are functioning. The fingerprints have formed, and the baby continues to suck their thumb. Tooth buds are now developing.

What You're Seeing: In this profile shot, notice that the fetus is lying with their bottom on the left-hand side of the image and the head to the right. The sonographer will probably not be able to define the baby's sex yet, but the legs are clearly visible raised up with knees bent. Note that genitals

The line across the middle of the profile is the sonographer's measurement of the baby's crown-rump length (CRL). With this measurement, the sonographer is able to accurately estimate your baby's age.