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Don't rush your baby's birth day

More and more births are being scheduled a little early. Experts are learning that this can cause problems. If possible, it's best to stay pregnant for at least 39 weeks. If your pregnancy is healthy, wait for labor to begin on its own.

Babies aren’t fully developed until at least 39 weeks of pregnancy.

If your pregnancy is healthy, wait for labor to begin on its own.
39 Weeks First Slide

Important brain development happens during the last weeks of pregnancy.

A baby’s brain at 35 weeks weighs only two-thirds of what it will weigh at 39 to 40 weeks.
39 Weeks Second Slide

Babies born after 39 weeks have fewer health problems than babies born early.

They also will have an easier time feeding and staying warm.
Read more: Premature birth
39 Weeks Third Slide

Be informed and ask questions.

If your provider talks to you about inducing labor or having a c-section, ask if there’s a problem with your health or the health of your baby.
39 Weeks Fourh Slide

If your labor is induced, your chances double for needing a c-section.

Sometimes induction is needed for medical reasons. If your pregnancy is healthy, it’s best to wait for labor to begin on its own.
39 Weeks Fifth Slide

What is happening this week in your pregnancy?

In the early weeks of your pregnancy, your baby is growing rapidly. But your baby's development during the last weeks is also important! Find out what happens each week.


How many weeks pregnant are you?

  • Week 1 - 4

    Conception usually happens 2 weeks after the start of your last menstrual period (also called LMP). Conception is when a man’s sperm fertilizes a woman’s egg. Most women don’t know the day they got pregnant. This is why health care providers use your LMP to find out how far along you are in pregnancy.

  • Week 1 - 4 (continued)

    Once the egg is fertilized, it attaches to the lining of the uterus and begins to grow.

  • Week 5

    Your baby’s neural tube has formed. The neural tube becomes your baby’s brain and spinal cord.

  • Week 6

    Your baby’s heart beats about 80 times a minute. Her nose, mouth and ears begin to take shape. Tiny buds start to appear that will become her arms and legs.

  • Week 7

    Your baby’s bones start to form but are still soft. They harden as you get farther along in your pregnancy. Your baby’s genitals begin to take shape. But it’s probably too soon to know your baby’s sex. She now has eyelids, but they are sealed shut.

  • Week 8

    All of your baby’s major organs and body systems are developing.The placenta is working. The placenta grows in your uterus and supplies the baby with food and oxygen through the umbilical cord. Your baby is about ½ to 1 inch long.

  • Week 9

    Your baby’s arms grow and bend at the elbow. Her toes and ears begin to take shape. Tiny buds appear that become your baby’s teeth.

  • Week 10

    Fingers and toes continue to develop and grow nails. Your baby’s head becomes round in shape. Her neck is developing. All of her organs are formed, but they’re not fully developed.

  • Week 11

    Your baby’s bones begin to get hard. Her skin is still thin and see-through but gets less see-through over time. Her head makes up about half of her size.

  • Week 12

    Your baby’s hands develop faster than her feet. She moves around, but you may not be able to feel her move yet. You can hear your baby’s heartbeat through a device your provider uses. She’s about 3 inches long and weighs about 1 ounce.

  • Week 13

    Your baby is growing fast as her organs continue to develop. Your baby’s kidneys make urine. On an ultrasound, it may look like your baby is breathing and swallowing. This week is the end of your first trimester. Each trimester lasts about 3 months.

  • Week 14

    This is the beginning of your second trimester. Your baby starts to move her eyes. Her nose and taste buds are developing. Her skin starts to thicken, and hair follicles under her skin begin to grow.

  • Week 15

    Your baby is very active! She can flip and roll around inside you. You may begin to feel her move. Her bones are growing strong, and you may be able to see them during an ultrasound.

  • Week 16

    Your baby’s ears have developed. She can hear you! Talk or sing to her as much as you like. Your baby is about 6 to 7 inches long and weighs about 5 ounces.

  • Week 17

    Your baby starts to add fat to her body! Fat gives your baby energy and helps her stay warm after she’s born. Vernix starts to appear on your baby’s skin. This is waxy or greasy coating that’s waterproof. It protects your baby’s skin in the womb.

  • Week 18

    Your baby goes to sleep and wakes up throughout the day. Loud noises and your movements can wake her. Her skin has lanugo. This is soft, fine hair that helps keep her warm in the womb.

  • Week 19

    Your baby’s kicks and movements are getting stronger! If you think you felt her movements before, you really can feel them now. She starts to learn how to suck, which she needs for feeding after she’s born.

  • Week 20

    Your baby is swallowing more. Her nails start to grow toward the ends of her fingers. If you want, you can find out if your baby's a boy or a girl on an ultrasound. Your baby is about 10 inches long and weighs about 1 pound.

  • Week 21

    Your baby’s fingers and toes are fully formed, including her finger prints and toe prints. From time to time, she may hiccup. You may feel these as regular, jerky movements.

  • Week 22

    Your baby’s eyelids are still shut, but her eyes are moving behind them. Her tear ducts start to develop, and her eyebrows may begin to appear. She may move suddenly when she hears loud sounds.

  • Week 23

    Your baby may recognize familiar sounds, like your voice. She may suck her thumb. The sex organs are developed. For boys, their testes begin to hang down. For girls, their uterus, ovaries and eggs are in place. These eggs could become your future grandchildren--how cool is that?

  • Week 24

    Your baby’s muscles continue to develop. She may start to have hair on her head. Her lungs are fully formed but aren’t ready to work outside the womb. She is about 12 inches long and weighs about 1 to 1½ pounds.

  • Week 25

    Your baby is growing and developing fast! Your baby also adds more fat to her body, which makes her skin look smooth and less wrinkly.

  • Week 26

    Your baby’s lungs start to make surfactant. This substance helps your baby’s lungs get ready to breathe.

  • Week 27

    Your baby is doing lots of kicking and stretching. Her lungs and nervous system continue to develop. This week marks the end of your second trimester.

  • Week 28

    This is the beginning of your third trimester. Your baby can slightly open her eyes and can sense changes in light. Her eyelids begin to form eyelashes. Your baby is about 10 inches long and weighs about 2½ pounds.

  • Week 29

    Your baby starts to put on weight fast! In the last 2½ months of pregnancy, your baby gains about half her birthweight. Be sure to eat healthy so your baby has the nutrients she needs to grow.

  • Week 30

    Your baby begins to lose the lanugo, the soft fine hair that covered her body. She also may have a good amount of hair on her head! Your baby is about 10½ inches long and weighs about 3 pounds.

  • Week 31

    Your baby’s brain grows and develops. Parts of her brain can control her body heat without depending on the temperature of the amniotic fluid. Amniotic fluid is fluid that that surrounds your baby in the womb.

  • Week 32

    As your baby adds fat to her body, her skin is no longer see-through. Even though your baby’s lungs aren’t fully developed, she practices breathing. Your baby is about 18 inches long and weighs about 4 to 5 pounds.

  • Week 33

    Your baby gains weight quickly. As you get closer to your due date, your baby gains about ½ pound per week. She gains weight, but doesn’t get much longer than 20 inches. The pupils in her eyes can respond to light.

  • Week 34

    Your baby’s fingernails reach the ends of her fingers. The vernix, the waxy, greasy coating that protects your baby’s skin in the womb, starts to get thicker. Your baby also develops sleep patterns and likes to sleep at certain times during the day.

  • Week 35

    Your baby’s brain, eyes, ears and lungs are still developing. A baby’s brain at 35 weeks weighs only two-thirds of what it will weigh at 39 to 40 weeks. If your pregnancy is healthy, wait for labor to begin in its own. Births scheduled before 39 weeks should be for medical reasons only.

  • Week 36

    It’s starting to get crowded in the womb! While she doesn’t have room to do many flips or rolls, you still feel her kicks, stretches and other movements. If you notice that your baby's moving less, contact your health care provider. Your baby is about 20 inches long and weighs about 6 pounds.

  • Week 37

    Important organs, like your baby’s brain, lungs and liver, are still developing. If your pregnancy is healthy, it’s best to stay pregnant for at least 39 weeks. Births scheduled before 39 weeks should be for medical reasons only.

  • Week 38

    Your baby’s toenails reach the ends of her toes. Your baby’s size may make you feel uncomfortable. If your pregnancy is healthy, wait for labor to begin on its own. Hang in there!

  • Week 39

    You and your baby have made it to 39 weeks! This is great! Your baby will let you know when she’s ready to be born. Call your provider when you think you’re in labor.

  • Week 40

    Congratulations on 40 weeks! Your baby’s had time to fully develop and is ready to meet you face to face. Call your provider when you think you’re in labor. Your baby is about 18 to 20 inches long and weighs about 6 to 9 pounds.

Visitors may have been directed to this web page through the efforts of the Centers for Medicare and Medicaid Services (CMS). CMS is partnering with the March of Dimes to increase awareness of the medical impact of babies being born before 39 weeks. CMS' involvement is for informational purposes only and should not be construed as an endorsement of the March of Dimes or its activities.

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