Pregnancy Pregnancy Development Stages Fetal Development Second Trimester Ultrasound Pictures We've partnered with the American Institute of Ultrasound Medicine, Johns Hopkins, and March of Dimes to create this unique peak into your baby's development inside the womb in the second trimester. By Kristen J. Gough Updated on June 2, 2023 Share Tweet Pin Email Trending Videos Prenatal ultrasounds are exciting for expecting parents because they get to see inside the womb and catch a glimpse of their baby-to-be. However, these exams usually only happen once or twice each pregnancy. For example, you might have an exam at 15 weeks (and get 15-week fetus ultrasound pictures) but not get an ultrasound at any other time during your second trimester. This leaves much of fetal development—and what your baby looks like each week—a mystery. However, since fetal development is fairly uniform, you don't have to look at your own baby-to-be's pictures to get an idea of what they likely look like. This slideshow of ultrasound pictures of the second trimester of pregnancy gives you a look at each week of development. Also included are detailed views of various parts of the body, such as the head, bones, heart, and lungs. You'll also see ultrasound pictures that can help to reveal a baby's sex. Editor's Note While this article uses the terms "gender" and "boy" vs. "girl," it's important to note that gender is a personal identity that exists on a spectrum, can change over the course of a person's lifetime—and most importantly—is something that a person defines for themselves. Sex, on the other hand, is assigned at birth based on the appearance of a baby's genitalia. While sex assigned at birth often matches a person's gender (called cisgender), sometimes, for transgender, intersex, and gender nonbinary people, it does not. 01 of 24 Second Trimester Begins: Weeks 13 to 17 of Pregnancy 02 of 24 14 Week Ultrasound American Institute of Ultrasound in Medicine - AIUM.org This ultrasound picture gives you a glimpse of what's going on with babies at 14 weeks of development. Fetal Size: Length, 3 1/4 to 4 inches, crown to rump; weight, around 1 ounce Fetal Development Milestones: Male or female genitalia are now formed. Your baby's liver and spleen are producing red blood cells. Also, their upper limbs are proportionate to the rest of the body. The lower limbs are slightly shorter. What You're Seeing: The sonographer has magnified the image to show the baby-to-be's profile. Their head is on the right-hand side of the image and their hand is on their chest. Your Guide to Baby Ultrasound Exams 03 of 24 15 Week Ultrasound American Institute of Ultrasound in Medicine - AIUM.org At 15 weeks, a fetal ultrasound picture typically shows the following: Fetal Size: Length, 4 to 4 1/2 inches, crown to rump; weight, 1 3/4 ounces Fetal Development Milestones: Your baby's skeletal system is continuing to develop. Characteristic hair patterns on the scalp are taking shape. What You're Seeing: In this 3D image, the baby-to-be is curled up, their hands covering their face. They are about the size of a grapefruit. The large bones that make up their skull are forming and hardening. As they harden, the bones appear whiter and brighter in the image. These cranium pieces do not come together until well after birth. How Big Is My Baby This Week? 04 of 24 16 Week Ultrasound American Institute of Ultrasound in Medicine - AIUM.org After 16 weeks of development, your little one's features are on display. Fetal Size: Length, 4 1/3 to 4 2/3 inches, crown to rump; weight, 2 3/4 ounces Fetal Development Milestones: Baby's lower limbs are now well developed. Toenails are forming and your baby's eyes and ears continue to move into the proper place. Facial muscles are beginning to work. What You're Seeing: In this closeup view of a baby's profile, you can see how their facial features are becoming more defined. Notice that the sonographer has measured the length of their nasal bone. This specialized measurement may be useful in screening for some genetic abnormalities. Week 16 Ultrasound: What It Would Look Like 05 of 24 17 Week Ultrasound American Institute of Ultrasound in Medicine - AIUM.org This ultrasound picture highlights the tiny hand of a 17-year-old fetus. Fetal Size: Length, 4 1/2 to 4 3/4 inches, crown to rump; weight, 3 1/2 ounces Fetal Development Milestones: Fetal bones are becoming more visible on ultrasound. You may be able to feel some fetal movement, particularly if you have been pregnant before. What You're Seeing: This close-up shows the baby-to-be's tiny right hand. You can see each bone within their delicate fingers. Although they may not be coordinated enough now to use their fingers (other than to wiggle!), by the time they're born they will have matured to the point where their fingers will have some dexterity—they'll even be able to grasp your finger with their hand! Week 17 Ultrasound: What It Would Look Like 06 of 24 18 Week Ultrasound: Head American Institute of Ultrasound in Medicine - AIUM.org A lot of big changes are happening in your baby's head during the 18th week! Fetal Size: Length, 5 to 5 1/2 inches, crown to rump; weight, 5 1/4 ounces Fetal Development Milestones: Your little one's ears are becoming more shapely. Facial features are now in their proper position. The baby's eyes are now developed enough to detect light. What You're Seeing: Halfway through your pregnancy (18-20 weeks) your health care provider may request an ultrasound to evaluate your baby's size and anatomy. This image shows a cross-sectional view of the baby's head. The sonographer will measure the baby-to-be's head circumference or biparietal diameter (BPD). 07 of 24 18 Week Ultrasound: Abdomen & Heart American Institute of Ultrasound in Medicine - AIUM.org Take a closer look at what's happening with heart and lung development at 18 weeks. Fetal Size: Length, 5 to 5 1/2 inches, crown to rump; weight, 5 1/4 ounces Fetal Development Milestones: Facial features are now in their proper position. The baby's bones continue to harden. What You're Seeing: This image shows a cross-sectional view of the baby's abdomen at the level of the stomach. The distance around the baby's abdomen, or abdominal circumference, is being measured. A complete standard second-trimester ultrasound includes images of your baby's chest, abdomen, and brain. The sonographer will also take measurements to evaluate your baby's growth. Week 18 Ultrasound: What It Would Look Like 08 of 24 18 Week Ultrasound: Bones American Institute of Ultrasound in Medicine - AIUM.org This ultrasound picture examines bone growth. Fetal Size: Length, 5 to 5 1/2 inches, crown to rump; weight, 5 1/4 ounces Fetal Development Milestones: Bones and nerve endings associated with hearing are developing. Baby's soft bones are beginning to harden too. What You're Seeing: In this image, the sonographer has marked the length of the femur (the thigh bone). From this measurement, the sonographer can evaluate your baby's growth. In the image on the right, you can see the bones of both of the baby's lower legs. 09 of 24 18 Week Ultrasound: Female Gender Reveal American Institute of Ultrasound in Medicine - AIUM.org If you're hoping to find out your baby's gender, an ultrasound exam can often show the baby's genitals by around 18 weeks. Fetal Size Length, 5 to 5 1/2 inches, crown to rump; weight, 5 1/4 ounces. Fetal Development Milestones: If you're having a girl, their ovaries are developed. What You're Seeing: A little girl! Determining your baby-to-be's gender isn't always easy. In this image, looking between the baby's legs, the sonographer can identify labia. Note that the baby doesn't always cooperate during an ultrasound exam, but here, there's no mystery. 10 of 24 18 Week Ultrasound: Male Gender Reveal American Institute of Ultrasound in Medicine - AIUM.org If your baby has a penis, it might be visible in an 18-week ultrasound. Fetal Size: Length, 5 to 5 1/2 inches, crown to rump; weight, 5 1/4 ounces Fetal Development Milestones: Male genitalia continue to form. What You're Seeing: It's a boy! In this image, it's almost as if the baby is sitting down, legs apart, so that their penis is clearly visible. The sonographer can't always determine a baby's sex during an ultrasound exam (and, of course, the exam is centered on the health of the fetus, not the baby's sex organs). But here, you can see the baby's penis in the center of the picture. 22 Tips for a Healthy Pregnancy 11 of 24 Boy or Girl: How Genetics Determine Your Baby's Sex 12 of 24 19 Week Ultrasound American Institute of Ultrasound in Medicine - AIUM.org This ultrasound picture highlights at limb development. Fetal Size: Length, 5 1/4 to 6 inches, crown to rump; weight, 7 ounces Fetal Development Milestones: Arms and legs are now well-developed and in proportion. What You're Seeing: Your baby's legs and arms are continuing to develop and add muscle. You may be able to feel your baby's movements now or within the next week or two. Week 19 of Your Pregnancy 13 of 24 20 Week Ultrasound American Institute of Ultrasound in Medicine - AIUM.org Check out the sweet little baby hand in this 20-week ultrasound picture. Fetal Size: Length, 5 2/3 to 6 1/2 inches, crown to rump; weight, 9 ounces Fetal Development Milestones: Hair and nails are continuing to grow. In girls, the uterus is now formed and the vaginal canal is also forming. You can feel fetal movements even more now! What You're Seeing: Here, the baby-to-be is curled up with their leg tucked in and their arms covering their face, which is turned away. They may look scrawny now, but developmentally, they're right on track. Their bones, visible in this 3D image, are continuing to harden and develop. Week 20 Ultrasound: What It Would Look Like 14 of 24 21 Week Ultrasound American Institute of Ultrasound in Medicine - AIUM.org At 21 weeks, your pregnancy is in its second half! Fetal Size: Length, 7 1/4 inches, crown to rump; weight, 10 1/2 ounces Fetal Development Milestones: The baby is swallowing amniotic fluid. Bone marrow is beginning to produce red blood cells. The baby moves and wiggles frequently. What You're Seeing: This profile image not only shows how your baby-to-be's bones and skeletal structures are forming but also their lungs. Looking at their chest, the sonographer can identify the heart and lung tissue. Week 21 Ultrasound: What It Would Look Like 15 of 24 Feeling Baby Move: Weeks 18 to 21 of Pregnancy 16 of 24 22 Week Ultrasound American Institute of Ultrasound in Medicine - AIUM.org At this stage, a baby-to-be is developing rapidly. Fetal Size: Length, 7 2/3 inches, crown to rump; weight, 12 1/4 ounces Fetal Development Milestones: The baby's hair may be growing, and eyebrows are beginning to form. Their sense of taste and smell are developing too. What You're Seeing: Here, the baby-to-be appears to be sleeping (babies in utero do have periods of sleeping and periods of activity). Week 22 Ultrasound: What It Would Look Like 17 of 24 23 Week Ultrasound American Institute of Ultrasound in Medicine - AIUM.org At 23 weeks, your little love is nearing viability. Fetal Size: Length, 8 inches, crown to rump; weight, almost 1 pound Fetal Development Milestones: Your baby-to-be is adding fat tissue and gaining weight. Rapid eye movements (REM) during dreaming are now beginning. What You're Seeing: With the baby-to-be crouched and their legs pulled in toward their chest, you can almost see their complete profile. Images of the baby's entire body are difficult now that they're more than 8 inches in length. They're about to experience a dramatic weight gain in the coming weeks. For now, they're still relatively thin. 5 Signs You're Having a Big Baby 18 of 24 24 Week Ultrasound American Institute of Ultrasound in Medicine - AIUM.org At 24 weeks, crucial development takes place in a baby's vital organs. Fetal Size: Length, 8 1/2 inches, crown to rump; weight, 11/4 pounds Fetal Development Milestones: Your baby-to-be is capable of reacting to noise with a blink-startle response. Their lungs are developing. What You're Seeing: The image on the left shows a magnified view of the four chambers of the baby-to-be's heart. The image on the right shows blood flowing from the upper chambers of the heart (the atria) into the lower chambers of the heart (the ventricles). The walls of the ventricles are more muscular than the atria because they have to pump blood to the baby's lungs and the rest of the body. Week 24 Ultrasound: What It Would Look Like 19 of 24 25 Week Ultrasound American Institute of Ultrasound in Medicine - AIUM.org Take a look at that cute little baby ear! Fetal Size: Length, 8 3/4 inches, crown to rump; weight, 1 1/2 pounds Fetal Development Milestones: Your baby-to-be's hearing has developed enough to hear their parent's voice. Hair is continuing to grow on the head. What You're Seeing: This close-up image of your baby-to-be's ear shows just how developed their features have become. Although their hearing is still rudimentary, by the time they're born they'll be able to recognize your voice from hearing it constantly in utero. Week 25 Ultrasound: What It Would Look Like 20 of 24 Developing Senses: Weeks 22 to 25 of Pregnancy 21 of 24 26 Week Ultrasound American Institute of Ultrasound in Medicine - AIUM.org At 26 weeks, a baby-to-be's features are as cute as a button. Fetal Size: Length, 9 1/4 inches, crown to rump; weight, nearly 2 pounds Fetal Development Milestones: Baby's eyelashes are forming and their scalp hair continues to grow. What You're Seeing: Hi, there! This image reveals a close-up look at your unborn baby's nose and mouth. It's almost as if their face is pressed up against a window. Week 26 Ultrasound: What It Would Look Like 22 of 24 27 Week Ultrasound American Institute of Ultrasound in Medicine - AIUM.org At 27 weeks, your baby-to-be is at the end of the second trimester. Fetal Size: Length, 9 2/3 inches, crown to rump; total length about 15 1/4 inches; weight, 2 pounds Fetal Development Milestones: The lungs are continuing to develop, and the liver is maturing. The baby's immune system is strengthening. What You're Seeing: Now that the baby-to-be is growing rapidly, it's harder to get a complete profile in the womb (they just don't fit in the picture anymore!). Even though they have more than tripled their weight since this trimester began, there's still plenty of growing left to do. This week marks the end of the second trimester—just one more trimester to go! Week 27 Ultrasound: What It Would Look Like 23 of 24 More About Prenatal Ultrasounds Lighthunter/Shutterstock In addition to taking place in the second trimester, ultrasounds are also sometimes done in the first trimester and third trimester. Most often, pregnant people have one ultrasound in the second trimester, and sometimes another ultrasound at the end of the third trimester, depending on the needs of their pregnancy. However, when and how many ultrasounds each pregnancy requires varies greatly. And while it's understandably thrilling to "see" your baby during these exams, ultrasounds should only be done for medical purposes and be performed by experienced technicians. Consult with your doctor about their recommendations for when you should get an ultrasound during your pregnancy. Are Ultrasounds Safe During Pregnancy? 24 of 24 More Information & Resources Vasily Deyneka/shutterstock All ultrasound images for this slideshow were provided by the sonographers of the Johns Hopkins Maternal-Fetal Diagnosis and Treatment Center. We are grateful to Christine Bird, BS, RDMS, RVT, chief obstetrical sonographer, and Jude Crino, M.D., medical director, for their assistance with this project. More examples of prenatal ultrasounds and other information on your baby's fetal development are available at the American Institute of Ultrasound in Medicine and March of Dimes. Key Takeaways Ultrasound exams provide a cherished window into your baby's development. Sadly, you can't sneak a peek each week as it's only recommended to have one to two exams in most pregnancies. Luckily, taking a look at ultrasound pictures from other people's pregnancies can give you the next best thing! What to Expect at Your First Ultrasound Was this page helpful? Thanks for your feedback! Tell us why! Other Submit Sources Parents uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Avoid Fetal "Keepsake" Images, Heartbeat Monitors. U.S. Food and Drug Administration. 2014.