Mayo Clinic Guide to a Healthy Pregnancy: From Doctors Who Are Parents, Too!

CHAPTER 8. Month 5: Weeks 17 to 20

It is the most amazing feeling! It feels just like someone is tickling me lightly from the inside. All of a sudden I feel this movement, and then it disappears before I can put my hand on my abdomen. These little touches are the joy of my day. I’m feeling my baby move. — Kelly

The fifth month often brings another joy of pregnancy. For many moms, it marks the first time they’re able to feel baby move inside. This movement often is greeted with relief — feeling baby move is an indication that all is well. Now, not only is your tummy getting bigger, but baby is tickling your insides!


During the fifth month, your little boy or girl will start to fill out more. Gradually, he or she is beginning to look more like the child you dream about. Baby is still very small, though. As you near the half-way point of your pregnancy, the child inside still weighs less than a pound!

Week 17 Eyebrows and the hair on your baby’s scalp continue to appear. Baby also continues to experience bouts of the hiccups. Although you aren’t able to hear them, you may begin to feel them, especially if this is your second baby.

This week, brown fat starts to develop under your baby’s skin. This will help keep your baby warm after birth, when the temperature change from your uterus to the outside world will be quite noticeable, to say the least. Your baby will add more layers of fat in the later months of your pregnancy.

Week 18 During week 18 your baby’s bones begin to harden, a process called ossification. Bones in your baby’s legs and inner ear are among the first to ossify. With the bones in the inner ear now developed enough to function and the nerve endings from your baby’s brain now hooked up to the ears, your baby can hear sounds. He or she may hear your heart beating, your stomach rumbling or blood moving through the umbilical cord. Your baby may even become startled by loud noises.

Your little one can also now swallow. Inside your uterus, your baby may be swallowing a good dose of amniotic fluid every day. Scientists think this may help keep your amniotic fluid at the appropriate, constant level.

Week 19 During week 19 your baby’s skin becomes covered with a slippery, white, fatty coating called vernix caseosa, or vernix for short. Vernix helps protect baby’s delicate skin, keeping it from becoming chapped or scratched. Under the vernix, fine, down-like hair called lanugo covers your baby’s skin.

Your baby’s kidneys are now developed enough to make urine. The urine is excreted into your amniotic sac, the bag of waters inside your uterus that contains your baby and your amniotic fluid. Unlike your urine, your baby’s urine is completely sterile because he or she is living in a sterile environment. Therefore, when your baby swallows amniotic fluid containing urine, it is not a problem.

His or her hearing is now well developed. Baby is probably hearing lots of different sounds, maybe even your conversations. Mom’s voice is by far the most prominent in any conversation. If you sing or talk to your baby, it’s reasonable to think he or she might notice. It’s less clear whether your baby is able to recognize particular sounds.

Your baby’s brain continues to develop millions of motor neurons, nerves that help the muscles and brain communicate. As a result, baby now may make conscious muscle movements, such as sucking a thumb or moving his or her head, as well as involuntary movements. You may or may not be able to feel these movements yet. If you haven’t, you will soon.

Week 20 Baby’s skin is thickening and developing layers this week, under the protection of the vernix. Skin layers include the epidermis, the outermost layer of skin; the dermis, the middle layer, which makes up 90 percent of the skin; and the subcutis, the deepest layer of skin, made up mostly of fat.

Your baby’s hair and nails continue to grow. If you could sneak a peek at your baby this week, you would see a fetus remarkably baby-like in appearance, with thin eyebrows, hair on the scalp and rather well-developed limbs.

Now at the halfway point of your pregnancy, you’ve probably begun to feel your baby’s movements. Make a note of the date, and tell your care provider at your next visit. Your baby is now about 6 inches long and weighs about 9 ounces — a little over half a pound.


As you reach the midway point of pregnancy, your uterus will expand to your navel. Unless you are quite tall, your pregnancy now is probably quite obvious.

At first, you may not recognize your baby’s movements. Some women describe the movements as feeling like “butterflies” in your stomach or a growling stomach. These early movements will be erratic. They’ll become more regular later in your pregnancy.

What’s happening and where As with previous months, your hormone levels continue to increase this month, influencing baby’s growth and affecting all of your organ systems.

Heart and circulatory system Your circulatory system continues to expand rapidly. As a result, your blood pressure will probably stay lower than normal this month and next.

Your body also continues to make more blood. The extra blood you’re producing is mostly plasma, the fluid portion of blood. Later, your body will increase production of red blood cells — provided you’re getting enough iron. Iron deficiency anemia, a condition marked by a decline in red blood cells, can result if you don’t get the iron you need each day to fuel increased production of red blood cells. The condition most often develops after 20 weeks of pregnancy and can make you tired and more susceptible to illness. But unless it’s severe, it’s unlikely to hurt your baby.

You may continue to experience some annoying side effects such as nasal congestion, nosebleeds and bleeding gums when you brush your teeth. These changes are the result of increased blood flow to your nasal passages and gums.

Respiratory system Stimulated by the hormone progesterone, your lung capacity continues to increase this month. With each breath, your lungs inhale and exhale up to 40 percent more air than they did before. You also may breathe slightly faster. Many women become aware of some shortness of breath.

Digestive system Under the influence of pregnancy hormones, your digestive system remains sluggish. Because of this and your expanding uterus, heartburn and constipation may continue. You’re not alone, if that helps. Half of all women experience heartburn or constipation during pregnancy.

Breasts Changes in your breasts may be especially noticeable this month. With more blood flowing to them and the milk-producing glands inside growing in size, they now may be almost two cup sizes larger than before you were pregnant. Veins in your breasts may be more visible now, too.

Uterus It goes without saying that your uterus is expanding. By your 20th week, it will reach your navel. When it reaches its full size, it will extend from your pubic area to the bottom of your rib cage. By now your expanding uterus is almost certainly affecting your center of gravity and, therefore, how you stand, move and walk. You may feel especially clumsy, and you may also experience continued aches and pains, especially in your back and lower abdomen.

Around the 20th week of pregnancy, you may feel a pulling or stabbing pain in your groin or a sharp cramp down your side, especially after making a sudden move or reaching for something. This pain results from stretching your round ligament, one of several ligaments that hold your uterus (see round ligament pain in the Symptoms Guide). The pain usually lasts several minutes before going away, but it’s not harmful. It’s a good idea, however, to discuss any continuous pain with your care provider.

Urinary tract Because your urine flow remains slow, you remain at continued risk of developing a urinary tract infection. You are urinating more often than normal because of your pregnancy. But if increased urination is accompanied by a burning sensation, pain, fever or a backache, you may have a urinary tract infection. Contact your care provider.

Bones, muscles and joints The ligaments supporting your abdomen are becoming more elastic, and the joints between your pelvic bones continue to soften and loosen. In addition, your lower spine is probably now curving backward to help keep you from falling forward. Together, these changes may cause you to experience some back pain.

Back pain can begin at any time during pregnancy, but it most commonly starts between the fifth and seventh months. You may find the pain to be a mere annoyance. However, if you had back problems before you became pregnant, the pain may be more severe and interfere with your daily activities. For more on back pain, see backache in the Symptoms Guide.

Vagina Vaginal discharge continues. The thin, white discharge is caused by the effects of hormones on the glands in your cervix and the skin of your vagina. It’s normal in pregnancy and isn’t cause for concern. Contact your care provider, though, if you have vaginal discharge that’s greenish or yellowish, strong-smelling, or accompanied by redness, itching and irritation of the vulva. These are signs and symptoms of a vaginal infection.

Skin You may continue to experience mild skin darkening on your face and around your nipples. Most of these changes are nothing to worry about. Changes in moles or new moles are the exception. If you have a new mole or a mole that has changed considerably in size or appearance, contact your care provider.

Weight gain You’ll probably gain about a pound a week this month, for a total of about 4 pounds. By the time you reach your 20th week, you may have gained about 10 pounds.


Is there really such a thing as “baby brain”?

There isn’t enough information to support the existence of baby brain — a term used to describe the idea that pregnancy or early motherhood can harm a woman’s memory and ability to think.

Researchers began studying the theory of baby brain because women frequently report cognitive changes, particularly forgetfulness, during pregnancy and shortly after becoming mothers. Studies examining the relationship between pregnancy or early motherhood and changes in a woman’s ability to think, however, have produced conflicting results. Some studies have shown that pregnancy impairs a woman’s memory during pregnancy and shortly afterward, possibly due to hormonal changes, sleep deprivation or the stress of coping with a major life change. However, other research has shown that pregnancy and motherhood have no negative cognitive impacts.

Because the concept of baby brain is so widely accepted, some experts suggest that pregnant women and new mothers are more aware of everyday cognitive slips. As a result, they mistakenly perceive themselves as having trouble thinking. If you’re pregnant or a new mother, don’t assume that you’re experiencing a cognitive decline. Keep in mind that becoming a mother involves an emotional and physical transition. While you’re adjusting, focus on the positive aspects of pregnancy, motherhood and the journey ahead.


The fifth month may bring a sense of reality. Not only is your tummy continuing to growth in size, you can now feel baby move. There’s no doubt, he or she is alive and kickin’.

Baby on the move! By your 20th week of pregnancy — or earlier if you’ve been pregnant before — it’s likely that you’ve begun to feel your baby move. These early movements are a great source of amusement and reassurance for most women. They’re also a more pleasant reminder of being pregnant than the nausea and fatigue of early pregnancy. In time, your partner will be able to feel your baby’s movements, too, by placing a hand on your abdomen.

You may be wondering if you can communicate with your baby at this point in your pregnancy. That’s hard to know. But it certainly can’t hurt to play soft music or talk soothingly to your baby. Besides, it makes you feel good!


Your visit to your care provider this month will again focus on tracking baby’s growth and watching for any problems with your own health. The usual steps will take place — checking your weight and blood pressure and measuring your fundal height. If you remember the date when you first felt your baby move, tell your care provider. This date will be one more piece of the puzzle in determining your baby’s age most accurately.

It’s at this time that you’ll have an amniocentesis test, if you’ve decided you want this test. An amniocentesis is performed for specific reasons; it’s not a routine exam. It’s important that you discuss the benefits, risks and limitations of the test with your care provider. With amniocentesis, a sample of the amniotic fluid is taken from the sac surrounding the baby. This sample can be tested to see if the baby has certain genetic abnormalities, such as Down syndrome.

For more information on this and other prenatal tests, see prenatal testing in Chapter 21.


At Mayo Clinic and in other medical practices across the country, a prenatal care approach called centering pregnancy is becoming more common. Here’s basically how it works: A group of women who have similar due dates gather together on a regular basis — it doesn’t matter if the woman is having her first baby or her fourth. This group continues to meet regularly throughout pregnancy. Partners are welcome, too.

At each centering pregnancy meeting, participants measure their weight and blood pressure. Then each participant gets one-on-one time with the nurse midwife or other care provider to address any personal questions or concerns, check the baby’s growth and listen to the baby’s heartbeat. After this individual time, the group then joins together. Sometimes there’s a prepared topic for the group to discuss, and other times a guest may speak for a while.

The primary focus of each meeting, however, is interaction with other participants, who are at the same point in their pregnancies as you are — women who are dealing the same issues, frustrations and joys. Basically, the group learns from each other. For example, it’s one thing for a care provider to tell you that back pain is normal during pregnancy — but it’s another thing for four other pregnant women to tell you that their backs hurt, too, and what steps they take to deal with the problem.

Unlike traditional classes or lectures, group prenatal care helps provide a sense of community. After all the babies are born, the centering group will often host a reunion to exchange birth stories, admire each other’s babies and share in the joy of the group.


During your pregnancy, you may hear or read about what’s called cord blood banking. And you may wonder if this is something you should do, or consider. Here’s some information about this procedure.

The blood within a baby’s umbilical cord is a rich source of stem cells, the cells from which all other cells are created. Cord blood banking is a procedure in which cord blood is taken from a baby’s umbilical cord shortly after delivery and preserved for possible future use in a stem cell transplant. Collecting a baby’s cord blood poses few, if any, risks to either mother or baby. If the cord blood isn’t collected for preservation or research, it’s simply discarded.

Public vs. private There are two main ways to bank cord blood. The first is using a public cord blood bank. Public banks collect and store cord blood for use by any individual who has a medical condition in which cord blood might provide a cure. The second type is a private bank. It oversees the collection and storage of cord blood for families who are willing and able to pay for the service, and the blood is saved for use by that family.

Should you consider it? Donating cord blood to a public cord blood bank is a tremendous opportunity to help others. Cord blood transplants from unrelated donors can be used to treat many conditions, including leukemia and various metabolic problems. You won’t be charged any fees to donate cord blood to a public bank. However, you may need to give birth to your baby at one of the limited number of hospitals or other facilities equipped to handle public cord blood donations.

Donating cord blood to a private facility for possible personal use is controversial. The cost is often considerable, and the chance that your child will use his or her own banked cord blood in the future is remote. Also, should your child need a stem cell transplant, there’s no guarantee that his or her banked cord blood will remain viable or be suitable for a transplant.

The American Academy of Pediatrics (AAP) encourages donation to public cord blood banks but discourages private donation. In recommending against private donation, the AAP states: “The chances of a child needing his or her own cord blood stem cells in the future are estimated to range from 1 in 1,000 to 1 in 200,000. Private cord blood banks target parents at an emotionally vulnerable time when the reality is most conditions that might be helped by cord blood stem cells already exist in the infant’s cord blood. However, the AAP does recommend private cord blood banking for parents who have an older child with a condition that could potentially benefit from transplantation, such as a genetic immunodeficiency.”

If you’re considering cord blood banking — whether it be a public or private donation facility — talk to your care provider. He or she can help answer any questions you may have and help you better understand the options so that you can make an informed decision.