The Second Trimester: Your Baby's Growth and Development in Middle Pregnancy
Month 4 of Pregnancy
WebMD Pregnancy App.
Your baby grows and changes fastduring your second trimester.Here's an inside peekat her amazing progress!By week 13, she's as largeas a lemon -- about 3 incheslong.And she's learning howto swallow by takingan occasional gulpof the amniotic fluidaround her.Next week, she's a little bigger-- the length of a bell pepper.But by week 15, your baby couldbe the size of a large russetpotato --around 6 inches long.Her bones get harderand stronger during week 16.Now she can flex her armsand legs.Plus, her eyes can slowly movearound behind closed lids.Next week she's the sizeof an asparagus spear -- almost8 inches long.And she's on the move,doing flips and rolls.She can also make a fistand hold it to her mouth.Her face gets more definedduring week 18.Those little eyelids, ears,and upper lipall come into sharper focus.Plus, she can hear sounds now.Your little one maybe over nineinches long --about the size of an eggplant --by week 19.Her lungs' main airways startto form.Something super adorable happensin week 20 -- your baby puts herfeet and toes in her mouth.She also gets lots of sleep.Noise and movement can wake herup -- so keep it down, would ya?(Just kidding.)Next week your 10 and 1/2-inchtot is making strong kicksand turns.She's also forming brown fatfor warmth.Your baby's genitals arecompletely formed around week22.It's possible to seeher eyebrows now, too.And soft, warm hair calledlanugo covers her.By week 23, her fingers and toeslook like tiny versions of yours-- and they've got fingerprints.Plus, your little one now hasa secret talent: she can hiccup.At week 24 your baby ispineapple-sized --about 12 1/2 inches long--and 1 1/2 pounds.She could surviveoutside your wombif she was born now.Your little one knows the soundof your voice at week 25.She can recognize other familiarsounds too ... when she's notsleeping.She snoozes 80% of the time now.By next week, she knows howto suck -- and she'll probablytry that skill out on her thumb.At the end of your secondtrimester on week 27,your little one is the lengthof an English cucumber -- over14 inches long.And all that moving aroundis paying off, giving her moreand 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.
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!
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.