Skip to content

Top Navigation

Parents Parents
  • GETTING PREGNANT
  • PREGNANCY
  • BABY NAMES
  • BABY
  • TODDLER
  • BIG KID
  • FUN
  • HEALTH
  • PARENTING
  • FOOD
  • HOLIDAY
  • News
  • THE STAY AT HOME GUIDE
  • SHOP
  • OUR MAGAZINES
  • MORE

Profile Menu

Your Account

Account

  • Join Now
  • Your Profile
  • Your Profile
  • Newsletters
  • Manage Your Subscription this link opens in a new tab
  • Give a Gift Subscription this link opens in a new tab
  • Cozi Family Organizer this link opens in a new tab
  • Help
  • Logout
Login
Subscribe
Pin FB

Explore Parents

Parents Parents
  • Explore

    Explore

    • 22 Chore Ideas for Every Type of Kid

      Find a chore your kid loves to do, and start a habit of wanting to help out that'll last a lifetime. Read More Next
    • Top 5 Mom Friend Problems—And How to Fix Them

      Parenting is so much easier with good pals. Learn to overcome friendship hurdles and bond with women who get you. Read More Next
    • How to Sleep Train Toddlers and Big Kids

      I’m a pediatric sleep specialist who has seen it all, and I’m here to tell you that it’s not too late to get your child to (happily) stay in his own bed all night long. Read More Next
  • GETTING PREGNANT

    GETTING PREGNANT

    See All GETTING PREGNANT

    Your Chances of Getting Pregnant Every Day of the Month

    When sex coincides withĀ your most fertile ovulation days, you'llĀ increase the chances of conceiving.Ā Get to know each phase of your cycle to get pregnant faster.
    • Ovulation
    • Reproductive Age
    • Maximizing Your Fertility
    • Pre-Pregnancy Health
    • Trying to Conceive
    • Dealing With Infertility
    • Genetics
  • PREGNANCY

    PREGNANCY

    See All PREGNANCY

    Signs of Approaching Labor: How to Tell Your Baby is Coming Soon

    Anxiously awaiting your baby’s arrival? Learn to recognize the first signs of labor approaching, which signal that your little one might make an appearance soon.
    • Signs of Pregnancy
    • Pregnancy Week-by-Week
    • Giving Birth
    • Labor & Delivery
    • Pregnancy Symptoms
    • Due Date Calculator
    • Pregnancy Complications
    • Fetal Development
    • Gender Prediction
    • Baby Showers
  • BABY NAMES

    BABY NAMES

    See All BABY NAMES

    These Are the Most Popular Baby Names of 2020

    Curious which baby names stole the show this year? From new classics like Noah to tried-and-true faves like Ava, here are the top boy and girl names of the year so far, plus more naming trends to consider.
    • Baby Girl Names
    • Most Popular Names
    • Names by Origin
    • Twin Names
    • Baby Boy Names
    • Names by Religion
    • Celebrity Baby Names
    • Baby Name Quizzes
  • BABY

    BABY

    See All BABY

    How to Decode Your Baby's Cough

    Caring for a baby with a wet or dry cough? Listen for wheezing, hacking, or barking first, then read on to find out what's normal and when it's time to worry.
    • Newborn Care
    • Crying Baby
    • Health
    • Baby Development
    • Safety
    • Gear
    • Breastfeeding
    • Diapers
    • Sleep Issues
    • Feeding
    • Nursery
  • TODDLER

    TODDLER

    See All TODDLER
    • Preschool Activities
    • Behavior & Discipline
    • Toddler Development
    • Milestones
    • Potty Training
    • Starting School
    • Health
    • Safety
    • Childcare
  • BIG KID

    BIG KID

    See All BIG KID

    How to Deal With Bullies: A Guide for Parents

    Mean kids aren't just a middle-school problem. The trouble has trickled to the youngest grades. Learn how to spot it—and how to protect children of all ages from bullies at school.
    • Education
    • Health
    • Food & Nutrition
    • Bullying & School Problems
    • Child Development
    • Safety
    • Manners & Responsibility
  • FUN

    FUN

    See All FUN

    17 Budget-Friendly Kids’ Birthday Party Ideas

    A fun celebration doesn’t need to cost a pretty penny. Throw a memorable bash with these clever cost-cutting kids’ birthday party ideas.
    • Birthdays
    • Indoor Activities
    • Outdoor Activities
    • Arts & Crafts
    • Printable Coloring Pages
    • Kids' Entertainment
    • Best Toys
    • Holidays
    • Family Vacation Ideas
  • HEALTH

    HEALTH

    See All HEALTH

    All About Coronavirus COVID-19: A Concerned Parent's Guide

    Here’s everything you need to know about the disease that originated in Wuhan, China.
    • ADD & ADHD
    • Allergies
    • Autism
    • Cold & Flu
    • Coronavirus and COVID-19
    • Cough
    • Down Syndrome
    • Emergency Aid
    • Fever
    • Medication & Vitamins
    • Obesity
    • Rashes
    • Stomach Aches
    • Vaccines
  • PARENTING

    PARENTING

    See All PARENTING

    The Stay at Home Guide for Parents

    Everything you need to thrive at home as a family.
    • Positive Parenting
    • Parenting Style
    • Celebrity Parents
    • Family Dynamics
    • Divorce
    • Home
    • Adoption
    • Just for Mom
    • Money
    • Toy Recalls
    • Stroller Recalls
  • FOOD

    FOOD

    See All FOOD
    • Family Recipes
    • Baby Food
    • Toddler Finger Food Recipes
    • Hints & Tips
    • Healthy Eating
    • Birthdays
    • Holiday Recipes
    • Quick & Easy Meals
    • Food For Pregnant Women
  • HOLIDAY

    HOLIDAY

    See All HOLIDAY

    44 Fun Valentine's Day Crafts for Kids

    Spend an afternoon making these Valentine's Day cards, decorations, and edible projects for kids. Bonus: These craft ideas are perfect for preschoolers and the ideal homemade gift for a few special someones!
    • Christmas
    • New Year's
    • Valentine's Day
    • Easter
    • Mother's Day
    • Memorial Day
    • Father's Day
    • 4th of July
    • Halloween
    • Thanksgiving
    • Hanukkah
  • News
  • THE STAY AT HOME GUIDE
  • SHOP
  • OUR MAGAZINES

    OUR MAGAZINES

    See All OUR MAGAZINES
    • Parents
    • Parents Latina
    • Ser Padres
  • MORE

    MORE

    • Newsletters
    • Contests
    • ParentsIRL
    • Adulting
    • First Year Playbook
    • Celebrate Your Way

Profile Menu

Subscribe this link opens in a new tab
Your Account

Account

  • Join Now
  • Your Profile
  • Your Profile
  • Newsletters
  • Manage Your Subscription this link opens in a new tab
  • Give a Gift Subscription this link opens in a new tab
  • Cozi Family Organizer this link opens in a new tab
  • Help
  • Logout
Login
Sweepstakes

Follow Us

  1. Home
  2. Pregnancy & Birth
  3. Pregnancy Development Stages
  4. Fetal Development
  5. Twins: A Closer Look at Your Developing Babies

Twins: A Closer Look at Your Developing Babies

By Kristen J. Gough
April 27, 2010
Skip gallery slides
Save Pin
Credit: iStock
Parents.com partnered with the American Institute of Ultrasound Medicine (AIUM) to create this unique peak into a baby's development inside the womb. These images reveal all the intricate details of a baby's growth -- from a collection of cells to a full-term newborn. While most women may only receive one or two ultrasounds during pregnancy, which is normal, this slideshow of the 3rd trimester of pregnancy gives you a look at each week of development.
Start Slideshow

1 of 13

Save Pin
Facebook Tweet Mail Email iphone Send Text Message

Week 6 (4 weeks from conception)

Credit: American Institute of Ultrasound in Medicine - AIUM.org

Fetal size: Length, 1/6 to 1/4 of an inch, crown to rump. Weight, still too small to measure.

Fetal development milestones: This week the babies are registering fetal heartbeats. Blood is pumping through their hearts. There are now two distinct amniotic sacs and the twins' heads, legs, and umbilical cords are forming.

What you're seeing: Although this may not look like much, these circles show two distinct gestational sacs -- twins! With a single pregnancy, only one sac would appear on the screen. Here, the sonographer (ultrasound technician) has identified each baby-to-be, one marked AA, the other BB. Most expectant mothers receive several ultrasounds during a twin pregnancy to ensure that both babies are growing properly and the pregnancy is progressing normally. Your unborn babies will grow at the same rate as with a single pregnancy -- but times two.

  • Read more about your babies in week six.

1 of 13

Advertisement
Advertisement

2 of 13

Save Pin
Facebook Tweet Mail Email iphone Send Text Message

Week 11 (9 weeks from conception)

Credit: American Institute of Ultrasound in Medicine - AIUM.org

Fetal size: Length, 1.61 inches, crown to rump. Weight, 0.25 ounces.

Fetal development milestones: Lots of little arms and legs are growing and elongating this week! Facial features are developing, as are fingers and toes.

What you're seeing: Just 11 weeks into your pregnancy, nine from conception, your unborn babies' faces are becoming more recognizable, with ears and eyes gradually moving into the proper place. Where there were once only small buds, arms and legs are now growing. Each baby has her own amniotic sac and umbilical cord. In this image, the sonographer has marked each twin, one with an A, the other with a B. The baby marked A is always the one closest to the cervix. Here, you can see the cervix in the lower right-hand corner of the image as the grayish form that comes near baby A. This baby has her head facing the cervix (notice the white facial bones), while baby B has her back toward the membrane that separates the two babies.

  • Read more about your babies in week 11.

2 of 13

3 of 13

Save Pin
Facebook Tweet Mail Email iphone Send Text Message

Week 13 (11 weeks from conception)

Credit: American Institute of Ultrasound in Medicine - AIUM.org

Fetal size: Length, almost 3 inches, crown to rump. Weight, almost 1 ounce.

Fetal development milestones: Kidney and urinary tracts are now functioning. Your babies can suck on their thumbs. Genitalia are developing too.

What you're seeing: In this 3-D image of your growing babies, you can see how each baby is developing much like he would in a single pregnancy. Notice that the babies' heads are more prominent than their growing limbs. Soon their arms and legs will be in proportion to the rest of their bodies. With just the right angle, the sonographer may be able to view each baby's gender. But at this early point in the pregnancy, the babies' sex will still be difficult to determine.

  • Read more about your babies in week 13.

3 of 13

Advertisement

4 of 13

Save Pin
Facebook Tweet Mail Email iphone Send Text Message

Week 14 (12 weeks from conception)

Credit: American Institute of Ultrasound in Medicine - AIUM.org

Fetal size: Length, 3 1/4 to 4 inches, crown to rump. Weight, around 1 ounce.

Fetal development milestones: Your babies' male or female genitalia are forming. Tissue under their faces and limbs is beginning to harden into bone. Their livers and spleens are producing red blood cells. Upper limbs are becoming proportionate to the rest of their bodies (although lower limbs are still underdeveloped).

What you're seeing: Now into your second trimester, your babies' bones are beginning to harden in a complex process called ossification, where inorganic and organic compounds come together to help the skeleton harden. If you look closely at each baby's head you can see the ossified white outlines of the bones in the skull. Baby A has his back toward the right side of the image, so his face is toward the membrane. His twin, baby B, has his back to the membrane (notice the white line of balls indicating the spinal column), his arm to his side.

  • Read more about your babies in week 14.

4 of 13

5 of 13

Save Pin
Facebook Tweet Mail Email iphone Send Text Message

Week 18 (16 weeks from conception)

Credit: American Institute of Ultrasound in Medicine - AIUM.org

Fetal size: Length, 5 to 5 1/2 inches, crown to rump. Weight, 5 1/4 ounces.

Fetal development milestones: The babies' senses are beginning to function. Facial features are now in their proper position. Fat tissue is developing. And you may be feeling fetal movement!

What you're seeing: Almost halfway into your pregnancy, your babies' eyes can detect light and their ears pick up on some sounds. Your unborn babies' facial features are continuing to become more refined. In this image, baby B has her back to the right side of the picture. Notice the white grouping, which indicates her spinal column. The dark circular form is her heart, and the faint, bubble-looking form above her is the umbilical cord. Baby A's umbilical cord is also visible at the top of the baby's body. The membrane that separates the two growing babies can move and sway as the fluid in the uterus moves -- or as the babies wiggle. Here, it's swaying toward baby B.

  • Read more about your babies in week 18.

5 of 13

6 of 13

Save Pin
Facebook Tweet Mail Email iphone Send Text Message

Week 19 (17 weeks from conception)

Credit: American Institute of Ultrasound in Medicine - AIUM.org

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. The babies' skin is now covered with cheeselike vernix as protection. Fat is beginning to build up, especially around sensitive areas like the neck, sternum, and kidneys.

What you're seeing: It's nearly impossible for the sonographer to capture a picture of both your babies' body profiles. In this image you can see that one baby, BB, is positioned with his head nudging the membrane that separates the two. The other baby, marked here as AA, is looking up and to the left of the image. You may begin to feel all this movement and heads shifting position. While your babies' arms and legs are now well-developed, their movements will still feel like little more than a flutter. In coming weeks, their kicks and jabs will become much more recognizable -- and forceful!

  • Read more about your babies in week 19.

6 of 13

Advertisement
Advertisement
Advertisement

7 of 13

Save Pin
Facebook Tweet Mail Email iphone Send Text Message

Week 20 (18 weeks from conception)

Credit: American Institute of Ultrasound in Medicine - AIUM.org

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 forming. You should be able to really feel movement now!

What you're seeing: As your babies grow larger, there's less room for them to maneuver in the womb. In this image the babies look as though their heads are touching. Often the babies' heads will rub together or touch, separated only by the thin membrane that lies between the two. With this image the sonographer is confirming that indeed there are two babies developing in the womb and also that the babies' heads are about the same size. If one head is significantly larger than the other, the sonographer may make additional measurements to ensure that both babies are developing properly. Different fetal head sizes may indicate a potential problem in the pregnancy.

  • Read more about your babies in week 20.

7 of 13

8 of 13

Save Pin
Facebook Tweet Mail Email iphone Send Text Message

Week 26 (24 weeks from conception)

Credit: American Institute of Ultrasound in Medicine - AIUM.org

Fetal size: Length, 9 1/4 inches, crown to rump. Weight, nearly 2 pounds.

Fetal development milestones: Fingernails are fully developed. Eyelashes are forming and scalp hair continues to grow.

What you're seeing: In this image you can see how the unborn babies' heads are touching in utero. The hand pointers that the sonographer has placed on the picture point out the babies' hair. At this point in development, unborn babies have been growing hair on their scalps for some time. While not every baby has hair on her head at birth, these two will have some curly locks!

  • Read more about your babies in week 26.

8 of 13

9 of 13

Save Pin
Facebook Tweet Mail Email iphone Send Text Message

Week 27 (25 weeks from conception)

Credit: American Institute of Ultrasound in Medicine - AIUM.org

Fetal size: Length, 9 2/3 inches, crown to rump; total length about 15 1/4 inches. Weight, 2 pounds.

Fetal development milestones: Lungs are continuing to develop, and your babies' livers are maturing. Their immune systems are also strengthening.

What you're seeing: Triplets! Marked with A, B, and C, this image captures three babies' heads in one image. It's very unusual for wiggly babies in utero to come together so that a sonographer can fit all three into the view screen. Looking at each head, you can see the bright white outline of the ossified, or hardening, skull bones. As with marking twins in utero, the sonographer tags the baby closest to the cervix with an A, the next closest, B. That will also be the order in which the babies are born.

  • Read more about your babies in week 27.

9 of 13

Advertisement
Advertisement
Advertisement

10 of 13

Save Pin
Facebook Tweet Mail Email iphone Send Text Message

Week 28 (26 weeks from conception)

Credit: American Institute of Ultrasound in Medicine - AIUM.org

Fetal size: Length, 10 inches, crown to rump; total length 15 3/4 inches. Weight, almost 2 1/2 pounds.

Fetal development milestones: Added brain tissue is developing, and your babies' scalp hair continues to grow. Your babies are gaining weight and opening their eyes.

What you're seeing: At 28 weeks' gestation, your babies are beginning to get scrunched in their home inside your womb. Although you can't see the membrane in this image, a thin wall separates the two babies. Here, the bright white lines represent ossified, or hardened, facial bones in each baby's head. You may notice that your babies' movements become more sluggish as they have less wiggle room.

  • Read more about your babies in week 28.

10 of 13

11 of 13

Save Pin
Facebook Tweet Mail Email iphone Send Text Message

Week 36 (34 weeks from conception)

Credit: American Institute of Ultrasound in Medicine - AIUM.org

Fetal size: Length, 13 1/2 inches crown to rump; total length 20 1/4 inches. Weight, 6 pounds.

Fetal development milestones: A big, healthy weight gain! All body systems are now developed and functioning.

What you're seeing: Only a few more weeks until delivery day! With a twin pregnancy, you're most likely to receive several ultrasounds to confirm that your babies are developing on schedule. As you near your babies' due date, your health care provider may request an ultrasound examination to check the babies' position in the uterus. Here, the two babies are lying cheek to cheek with only a thin membrane separating them.

  • Read more about your babies in week 36.

11 of 13

12 of 13

Save Pin
Facebook Tweet Mail Email iphone Send Text Message

More About Prenatal Ultrasounds

Credit: American Institute of Ultrasound in Medicine - AIUM.org

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.

For examples of prenatal ultrasounds and more information on your baby's fetal development, be sure to visit www.aium.org and www.marchofdimes.org.

Click here for additional prenatal ultrasounds and information:

  • First Trimester: Images of Your Developing Baby
  • Your Baby In the Second Trimester
  • Ultrasounds from Baby's Third Trimester

12 of 13

Advertisement
Advertisement
Advertisement

13 of 13

Save Pin
Facebook Tweet Mail Email iphone Send Text Message

For More Information

Credit: iStock

For more information about ultrasounds and fetal development, check out the following resources:

  • A Trimester-by-Trimester Guide to Ultrasounds
  • 4 Things to Know About Ultrasounds
  • Your Personal Pregnancy Calendar

13 of 13

Replay gallery

Share the Gallery

Pinterest Facebook

Up Next

Share the Gallery

Pinterest Facebook
Trending Videos
Advertisement
Skip slide summaries

Everything in This Slideshow

Advertisement

View All

1 of 13 Week 6 (4 weeks from conception)
2 of 13 Week 11 (9 weeks from conception)
3 of 13 Week 13 (11 weeks from conception)
4 of 13 Week 14 (12 weeks from conception)
5 of 13 Week 18 (16 weeks from conception)
6 of 13 Week 19 (17 weeks from conception)
7 of 13 Week 20 (18 weeks from conception)
8 of 13 Week 26 (24 weeks from conception)
9 of 13 Week 27 (25 weeks from conception)
10 of 13 Week 28 (26 weeks from conception)
11 of 13 Week 36 (34 weeks from conception)
12 of 13 More About Prenatal Ultrasounds
13 of 13 For More Information

Share options

Facebook Tweet Mail Email iphone Send Text Message

Login

Parents

Magazines & More

Learn More

  • About Us
  • Subscribe this link opens in a new tab
  • Customer Service this link opens in a new tab
  • Cozi Family Organizer this link opens in a new tab
  • Advertise this link opens in a new tab
  • Content Licensing this link opens in a new tab
  • From Our Sponsors this link opens in a new tab
  • Affiliate Program this link opens in a new tab
  • Sitemap

Connect

Follow Us
Subscribe to Our Newsletter
Other Meredith Sites

Other Meredith Sites

  • 4 Your Health this link opens in a new tab
  • Allrecipes this link opens in a new tab
  • All People Quilt this link opens in a new tab
  • Better Homes & Gardens this link opens in a new tab
  • Bizrate Insights this link opens in a new tab
  • Bizrate Surveys this link opens in a new tab
  • Cooking Light this link opens in a new tab
  • Daily Paws this link opens in a new tab
  • EatingWell this link opens in a new tab
  • Eat This, Not That this link opens in a new tab
  • Entertainment Weekly this link opens in a new tab
  • Food & Wine this link opens in a new tab
  • Health this link opens in a new tab
  • Hello Giggles this link opens in a new tab
  • Instyle this link opens in a new tab
  • Martha Stewart this link opens in a new tab
  • Midwest Living this link opens in a new tab
  • More this link opens in a new tab
  • MyRecipes this link opens in a new tab
  • MyWedding this link opens in a new tab
  • My Food and Family this link opens in a new tab
  • MyLife this link opens in a new tab
  • Parenting this link opens in a new tab
  • People this link opens in a new tab
  • People en EspaƱol this link opens in a new tab
  • Rachael Ray Magazine this link opens in a new tab
  • Real Simple this link opens in a new tab
  • Ser Padres this link opens in a new tab
  • Shape this link opens in a new tab
  • Siempre Mujer this link opens in a new tab
  • Southern Living this link opens in a new tab
  • SwearBy this link opens in a new tab
  • Travel & Leisure this link opens in a new tab
Parents.com is part of the Parents Network. © Copyright 2021 Meredith Corporation. All Rights Reserved. Privacy Policythis link opens in a new tab Terms of Servicethis link opens in a new tab Ad Choicesthis link opens in a new tab California Do Not Sellthis link opens a modal window Web Accessibilitythis link opens in a new tab
© Copyright . All rights reserved. Printed from https://www.parents.com

View image

Twins: A Closer Look at Your Developing Babies
this link is to an external site that may or may not meet accessibility guidelines.