Third Trimester Development

First trimester development
Second trimester development
Labor & delivery

Week 28

You're in the home stretch. The third trimester typically starts this week and lasts until 40 weeks and sometimes even beyond. (Don't worry — 42 weeks is the maximum! After that, a woman usually is induced to give birth.) Most women gain an average of 11 pounds during this trimester.

By this week, your baby weighs about 2 1/2 pounds and measures about 14 1/2 inches. At about this time, your baby can open his eyes and turn his head in utero if he notices a continuous, bright light shining from the outside. The fat layers are forming and the fingernails appear.

You're probably vacillating between feeling as if you've been pregnant forever and being nervous about childbirth. Checking off things on your to-do list can help. Start soliciting possible baby names and begin interviewing pediatricians.

If you aren't already, you'll probably start visiting your doctor once every two weeks until the eighth month, when you'll switch to weekly visits.

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Week 29

Your baby now weighs about 2 1/2 pounds and is about 14 1/2 inches long from head to toe. In boys, testicles move from near the kidneys through the groin en route to the scrotum. In girls, the clitoris is relatively prominent because it's not yet covered by the still-small labia, which will cover it in the last few weeks before birth).

The baby's head is getting bigger, and brain growth is very rapid at this time. Nearly all babies react to sound by 30 weeks.

Your baby's nutritional needs reach their peak during the third trimester. You'll need plenty of protein, vitamin C, folic acid, iron, and calcium (about 200 milligrams is deposited in your baby's skeleton every day). The skeleton hardens even more, and the brain, muscles, and lungs continue to mature.

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Week 30

Your baby's lungs and digestive tract are almost fully developed. And while your baby may soon grow more slowly in length, he will continue to put on the pounds.

This week your baby continues to open and shut his eyes. He can probably see what's going on in utero, distinguish light from dark, and even track a light source. If you shine a light on a your belly, your baby may move his head to follow the light or even reach out to touch the moving glow. Some researchers think baring your belly to light stimulates visual development. But don't expect 20/20 vision when your baby is born — newborns can see a distance of only about 8 to 12 inches. (Children with normal vision, don't reach 20/20 vision until about age seven to nine.) And to complete the picture, new eyebrows and eyelashes now frame your little one's peepers.

A pint and a half of amniotic fluid now surrounds your baby, but that volume decreases as he gets bigger and has less room in your uterus. As you and the baby continue to grow, don't be alarmed if you feel breathless, as if you can't get enough air; it's just your uterus pressing against your diaphragm. There is a light at the end of the tunnel, though. Usually about two to four weeks before labor (or during labor, if this is your second or third pregnancy), your baby's head will drop into your pelvis to get ready for delivery, and that will make breathing and eating a lot easier.

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Week 31

Your baby's arms, legs, and body continue to fill out — and they are finally proportional in size to his head. He weighs about 3 1/4 pounds and looks more like a newborn. You can expect your baby to gain at least two more pounds before delivery.

Pay attention to your baby's kicks and rolls now. Your perception of your baby's movements is an important tool in assessing your baby's well-being. Ideally, you should feel at least ten movements in two hours. If you notice a significant decrease in the frequency of the movements you've come to expect from your baby, you should tell your midwife or doctor immediately.

Your baby's organs are continuing to mature, and he is passing water from his bladder, good practice for the urinating he'll do after he's born. Soon you can wonder what your baby is wishing for — brain scans have shown fetuses have periods of dream sleep around month eight.

You've probably gained three to four pounds this month. Gaining a pound a week is quite normal during the last trimester — your baby has a final growth spurt before birth.

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Week 32

Your baby now weighs approximately 3 3/4 pounds and is about 16 1/2 inches long from head to toes. Though his lungs won't be fully developed until just before birth, your little one is inhaling amniotic fluid to exercise his lungs and practice breathing. Some babies have a head of hair already, others have only a few wisps. Thick hair at birth doesn't necessarily mean thick hair later on, but children with fine hair in childhood usually have thinner hair in adulthood.

If your baby is a boy, his testicles should be descending from his abdomen into his scrotum. Sometimes, however, one or both testicles won't move into position until after birth. Luckily, for two-thirds of all baby boys who have undescended testicles, the condition corrects itself by a boy's first birthday.

You're gaining a pound a week, largely because your baby is likely to gain more than half his birthweight during the seven weeks before delivery.

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Week 33

Your baby now weighs about 4 1/4 pounds and is approximately 17 inches long. Your baby should already be getting ready for delivery by turning upside-down — his head should be pointing down. Your doctor or midwife will be paying careful attention to your baby's position in the coming weeks — some babies do decide to turn back around.

Your baby's skull is still quite pliable and not completely joined, in part so he can ease out of the relatively narrow birth canal. But the bones in the rest of his body are hardening. Your baby's skin is also gradually becoming less red and wrinkled.

If you're a first-time mother, your child's head may move into the pelvis this week and press firmly against your cervix. (This happens for about half of all first-time mothers.) If you're a second-time mom, you can expect this to happen a week before labor — and for some this won't happen until the advanced stages of labor.

You may notice that your feet and ankles are quite swollen toward the end of the day. Water retention, also known as edema, is often worse in warm weather and late in the day. Surprisingly, keeping hydrated helps reduce water retention. Your body — particularly your kidneys — and your baby need plenty of fluids, so drink up. If you suddenly feel swollen or puffy in your hands or face, however, call your doctor — it may be a sign of preeclampsia.

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Week 34

Your baby now weighs more than 4 3/4 pounds and is probably about 17 1/2 inches long. She's filling out and getting rounder — she'll need her fat layers later to regulate her body temperature. If you don't already talk to your baby, you should start — by next week, your baby's hearing will be fully developed. And don't feel ridiculous if you're already chatting in baby talk. Some evidence shows that newborns pay closer attention to high-pitched tones.

If you've been nervous about going into preterm labor, you'll be happy to know that 99 percent of babies born at 34 weeks can survive outside the womb — and most have no major problems. Though your baby's central nervous system is still maturing, your baby's lungs are nearly fully developed by now.

Many women start to notice a tingling sensation or numbness in the pelvic region from the baby's weight on the nerves in the legs and pelvis. Unfortunately, this feeling probably won't subside until the baby is born. If you're terribly uncomfortable, mention it to your healthcare provider.

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Week 35

Your baby now weighs about 5 1/4 pounds and is approximately 18 inches long. These days your belly probably reminds you of the movie Alien. Your baby's elbow, foot, or head may protrude from your belly when she stretches and squirms about. And soon, as the wall of the uterus and the abdomen stretches thinner and lets in more light, your baby will begin to develop daily activity cycles. This week, your little one is sporting new fingernails and has a fully developed pair of kidneys. Her liver can also process some waste products.

There's much less amniotic fluid and much more baby in your uterus. You've probably put on between 25 and 30 pounds, and your weight gain has hit its zenith. Even your belly button it's gotten bigger and has popped outward. You may be feeling breathless now that the top of your uterus is up under your ribs. Try getting down on all fours to take deeper breaths. And although the pressure on your bladder will make the bathroom your second home, don't slow or stop drinking water — your baby needs the fluids. Just stay away from diuretic drinks like tea and coffee, which will make you have to urinate even more often.

Your doctor or midwife will probably want to start seeing you every week until you deliver. She may give you a handout on how to count fetal movements; if not, ask her for one.

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Week 36

Your baby is still putting on the pounds — about an ounce a day. She weighs between 5 and 6 pounds and is at least 18 inches long.

You may begin to feel an increased pressure in your lower abdomen and notice that your baby is gradually dropping. This is called lightening or engagement and your lungs and stomach will finally get a chance to stretch out a little — breathing and eating should become easier. However, walking may become increasingly uncomfortable — some women say it feels as if the baby is going to fall out. Also, you may still feel as if you need to go to the bathroom all the time.

The good news is that by the end of this week, your pregnancy will be full-term and you could give birth any day now. (Babies between 37 and 42 weeks are considered full-term — a baby born before 37 weeks is preterm and after 42 is post-term.) At your weekly visit, your doctor or midwife may check to see if you've started dilating (when the cervix opens) and effacing (when the cervix thins), and what position the baby is in, which is a way of estimating how far the baby has dropped into the pelvis. Make note of it so that once you're in labor you can tell your nurse at the hospital.

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Week 37

Your baby may weigh between 5 and 7 pounds at this point and is probably 19 to 20 inches long. Your baby's head is now cradled in your pelvic cavity — surrounded and protected by your pelvic bone. This position clears some much-needed space for her growing legs and buttocks.

Many babies now have a full head of hair, with locks from 1/2 to 1 1/2 inches long. But don't be surprised if her hair isn't the same color as yours. Dark-haired couples are sometimes thrown for a loop when their children are born with bright red or blond hair, and fair-haired couples have been rewarded with Elvis Presley look-alikes. And then, of course, some babies don't have any hair at all.

Speaking of hair, most of the downy coat of lanugo that covered your baby from 26 weeks has disappeared, and so has most of the vernix caseosa, the whitish substance that enshrouds the baby. Your baby will swallow her lanugo and exterior coating, along with other secretions, and store them in her bowels. These will become your infant's first bowel movement, a blackish waste called meconium.

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Week 38

Can you tell if you're carrying a boy or a girl? One hint may come from the size of your baby — boys tend to be slightly heavier than girls. Babies at 38 weeks tend to weigh 6 to 7 1/2 pounds and continue to build the fat stores that will help regulate body temperature after birth. Your little one's organ systems are fully developed and in place, but the lungs will be one of the last systems to reach real maturity. (Even after your baby is born, it may take a few hours before she establishes a normal breathing pattern.) The brain is the last organ to fully mature.

Wondering what color your baby's eyes will be? You may not be able to tell right away. If your baby is born with brown eyes, they'll likely stay brown. If your baby is born with steel gray or dark blue eyes, they may stay gray or blue or turn green, hazel, or brown by the time she's 9 months old. That's because a child's irises (the colored part of the eye) may gain more pigment in the months after she's born, but they won't get "lighter" or more blue. (Green, hazel, and brown eyes actually have more pigment than grey or blue eyes, even if they appear lighter in color.)

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Week 39

The average baby is about 20 to 22 inches long and weighs approximately 7 1/2 pounds at birth, but anywhere between 5 lbs., 11 1/2 ounces and 8 lbs., 5 3/4 ounces is a healthy range for newborns.

Your amniotic fluid, once clear, is now pale and milky from your baby's shedding vernix caseosa. The outer layers of skin are also sloughing off as new skin forms underneath.

In TV Land pregnant women always break their water — in the middle of a crowded room, of course — just before going into labor. If you've been worrying that this scenario will happen to you, you can stop. Membranes rupture unexpectedly in less than 15 percent of pregnancies, and when it does happen, the baby's head tends to act like a cork at the opening of the uterus, thus keeping the fluids from gushing out. (If you lie down, however, you may notice fluid leaking.) In this case, you should stay calm — it may be hours before you feel your first contraction — and call your doctor or midwife right away. Though your body will produce more amniotic fluid until the baby is born, your doctor may decide to induce labor to reduce the risk of infection.

And if the week passes and there's still no baby? Don't panic — only 5 percent of babies are born on their scheduled due date. Most doctors wait another one to two weeks before considering a pregnancy overdue.

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Week 40

You’re going to have a baby! Check out our labor & delivery section to see what happens next!

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First trimester development
Second trimester development
Labor & delivery
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Northeast Georgia Life, 2004