The Second Trimester: Your Baby's Growth and Development in Middle Pregnancy

Month 4 of Pregnancy

Video Transcript

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Your baby grows and changes fast during your second trimester. Here's an inside peek at her amazing progress! By week 13, she's as large as a lemon -- about 3 inches long. And she's learning how to swallow by taking an occasional gulp of the amniotic fluid around her. Next week, she's a little bigger -- the length of a bell pepper. But by week 15, your baby could be the size of a large russet potato -- around 6 inches long. Her bones get harder and stronger during week 16. Now she can flex her arms and legs. Plus, her eyes can slowly move around behind closed lids. Next week she's the size of an asparagus spear -- almost 8 inches long. And she's on the move, doing flips and rolls. She can also make a fist and hold it to her mouth. Her face gets more defined during week 18. Those little eyelids, ears, and upper lip all come into sharper focus. Plus, she can hear sounds now. Your little one maybe over nine inches long -- about the size of an eggplant -- by week 19. Her lungs' main airways start to form. Something super adorable happens in week 20 -- your baby puts her feet and toes in her mouth. She also gets lots of sleep. Noise and movement can wake her up -- so keep it down, would ya? (Just kidding.) Next week your 10 and 1/2-inch tot is making strong kicks and turns. She's also forming brown fat for warmth. Your baby's genitals are completely formed around week 22. It's possible to see her eyebrows now, too. And soft, warm hair called lanugo covers her. By week 23, her fingers and toes look like tiny versions of yours -- and they've got fingerprints. Plus, your little one now has a secret talent: she can hiccup. At week 24 your baby is pineapple-sized -- about 12 1/2 inches long-- and 1 1/2 pounds. She could survive outside your womb if she was born now. Your little one knows the sound of your voice at week 25. She can recognize other familiar sounds too ... when she's not sleeping. She snoozes 80% of the time now. By next week, she knows how to suck -- and she'll probably try that skill out on her thumb. At the end of your second trimester on week 27, your little one is the length of an English cucumber -- over 14 inches long. And all that moving around is paying off, giving her more and more muscle tone.

In the second trimester of pregnancy -- months 4, 5, and 6 -- your baby's fingers and toes are well-defined. His eyelids, eyebrows, eyelashes, nails, and hair are formed, and teeth and bones are becoming denser. Your baby can even suck his or her thumb, yawn, stretch, and make faces.

The nervous system is starting to function at this point in pregnancy. The reproductive organs and genitalia are now fully developed, and your health care provider can see on ultrasound if you are having a boy or a girl. Your baby's heartbeat may now be audible through an instrument called a Doppler.

By the end of the fourth month, your baby is about 6 inches long and weighs about 4 ounces.

16 Weeks

Month 5 of Pregnancy

Hair is beginning to grow on your baby's head, and lanugo, a soft fine hair, covers his or her shoulders, back, and temples. This hair protects your baby and is usually shed at the end of the baby's first week of life.

Your baby's skin is covered with a whitish coating called vernix caseosa. This "cheesy" substance, thought to protect baby's skin from long exposure to the amniotic fluid, is shed just before birth.

You may begin to feel your baby move, since he or she is developing muscles and exercising them. This first movement is called quickening.

By the end of the fifth month of pregnancy, your baby is about 10 inches long and weighs from 1/2 to 1 pound.

Now that you've read about your baby's development in the first 20 weeks of pregnancy, take this quiz to test your smarts!

20 Weeks

Month 6 of Pregnancy

By the end of the sixth month, your baby is about 12 inches long and weighs about 2 pounds. His or her skin is reddish in color, wrinkled, and veins are visible through the baby's translucent skin. Baby's finger and toe prints are visible. The eyelids begin to part and the eyes open.

Your baby may respond to sounds by moving or increasing the pulse, and you may notice jerking motions if baby hiccups.

If born prematurely, your baby may survive after the 23rd week of pregnancy with intensive care.

24 Weeks

WebMD Medical Reference Reviewed by Traci C. Johnson, MD on September 09, 2018

Sources

SOURCE: American Pregnancy Association.

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