What to expect


Expand the sections below to learn about each phase of pregnancy.

Week 2

Your uterus has shed its lining through your period and is now preparing a lush new bed of blood-rich tissue designed to house a growing fetus. Your eggs are ripening in one of the ovaries and preparing to release one.

Week 3

Sperm meets egg within the fallopian tube and the miracle of life begins. Although several sperm may penetrate the egg's outer layer, only one sperm will enter the ovum and fertilize it. In the middle of the ovum, the chromosomes of mother and father splash about and bits of information from both begin to form the chromosomes of your baby. At the moment of conception, your baby's gender is determined thanks to the sex chromosomes in the father's sperm. If you don't like the gender of your baby, blame dad.

Week 4

Taking root! Implantation occurs. Once the blastocyst gets to the uterus, it searches for a spot to settle down. Blastocyst means "sprout pouch," and these cells begin to divide into two groups - those that form the placenta and those that form the baby. The blastocyst will burrow itself into the lining of the uterus which is called implantation.

Week 5

The developing embryo has three layers. In the top layer (ectoderm), the neural tube will form which will further develop into the nervous system (brain, spinal cord, skin and hair). In the middle layer (mesoderm), the heart and circulatory system, bones, muscles, kidneys and reproductive organs will develop - eventually. At this stage, however, the heart and primitive circulatory system will rapidly form. In fact, the circulatory system is the first organ system to function. In the inner layer (endoderm), a simple tube will develop into the intestines, liver, pancreas and bladder.

Week 6

My Heart Belongs to You! The first heartbeats have begun! The baby is now an embryo and is about 1/17 of an inch long. Growth is very rapid this week. The umbilical cord develops. The eyes and ears begin to form as well as an opening for the mouth. The heart has begun to pump blood and most of the other organs are well under construction. Buds form on the body that will become the arms and legs.
Exciting week!

Week 7

I'm Tiny But Gaining Fast! The baby is about 1/3 of an inch, the size of a grain of rice. Development of the arms and legs continue although the fingers and toes haven't yet formed. The brain is growing as well as the lenses of the eyes, nostrils, intestines, pancreas and bronchi

Week 8

An ultrasound done at this stage should show a fluttering heartbeat. Elbows begin to form in the arms and fingers start to develop. The leg buds begin to show feet with tiny notches for the toes. The face continues to change as the ears, eyes and the tip of the nose appear. The intestines start to form in the umbilical cord. Teeth develop under the gums.

Week 9

Cartilage and bones begin to form. The basic structure of the eye is well underway and the tongue begins to develop. The intestines start to move out of the umbilical cord and into the abdomen as the body grows and makes room. The fingers and thumb have appeared but are short and webbed.

Week 10

I'm Swimming! The baby has begun moving inside the womb although it's too small for mom to notice. Most of the joints are formed now - elbow, wrist, knee, shoulder, and ankle as well as the hands, fingers, feet and toes.

Changes in Mom: The morning sickness may start to ease a bit. This week, we'll blame moodiness and a blotchy complexion on those wild hormones. Have heart ~ this is only temporary.

Week 11

I'm a Fetus! Starting with this week, the baby is now called a fetus. The most critical part of the baby's development is over. This is a period of rapid growth, and the baby is about an inch or so in length at the beginning of the week and will be about 2 inches by the end of the week. The baby's head is about half its length. The eyelids will fuse shut, and the irises will begin to develop. Sometime during this week or the next week, blood will begin to circulate between the baby and uterus and the placenta starts to function.

Changes in Mom: Your uterus is the size of a small grapefruit already! You may find that your appetite is better as your nausea subsides even though certain smells may bother you.

Week 12

By this point, nearly all of the organs and structures of the fetus are formed. They will continue to grow and develop until delivery. Fingers and toes have separated and hair and nails begin to grow. The genitals begin to take on their gender characteristics. Amniotic fluid begins to accumulate as the baby's kidneys begin to produce and excrete urine. The muscles in the intestinal walls begin to practice peristalsis - contractions within the intestines that digest food.

Changes in Mom: Around this week, your uterus will shift up and forward as it grows. The good news is it won't be pressing on your bladder so much and those bathroom visits will get less frequent. Enjoy this while you can because by the third trimester, the uterus will grow large enough to sit on your bladder once again. Morning sickness is usually getting better by this time, and you may be less tired. Headaches and light-headedness are common now thanks to the increased blood volume but be sure to discuss these symptoms with your care provider.

Week 13

As our baby continues to develop, the vocal cords begin to form. The face is looking more and more human each day as the eyes begin to move closer together instead of being on the sides of the head and the ears move to a normal position. It would be possible now to determine the baby's sex by looking at the genitals if we could only get close enough. (We usually can't "guess" via ultrasound until around the 16th week.) The intestines move farther into the baby's body; the liver begins to secrete bile and the pancreas begins to produce insulin. A very busy week indeed!

Changes in Mom: Welcome to the second trimester! This is the most comfortable and enjoyable stage of pregnancy. Most of the difficult early symptoms are over (or soon will be), and your tummy isn't getting in the way yet. If you're still feeling tired, listen to your body and REST. It's working hard right now!

Week 14

Our baby is a whopping 3 1/2 inches long and is 1 to 2 ounces. S/he begins to practice inhaling and exhaling movements. The eyes and ears continue to move and develop, the neck is still getting longer, and the baby's chin no longer rests on his/her chest. The hands are becoming functional, and the baby is beginning to learn to move/use them (probably more reflex than anything). At this point, our little one is receiving all of his/her nourishment from the placenta.

Changes in Mom: By now, pregnancy hormones are leveling off. This means less nausea, less frequent urination and less exhaustion. What a relief! However, you may be experiencing some constipation since those darned hormones have relaxed your bowel muscles causing them to work slower and less efficiently. Your uterus is also pressing on your bowel. Be sure to increase the fiber in your diet if constipation becomes a problem.

Week 15

If you have an ultrasound now, you may notice your baby sucking his/her thumb. The bones are getting harder each day. The baby's skin is very thin and transparent; you can see blood vessels through the skin. Lanugo, a very fine hair, covers the body and will continue growing on the baby until around the 26th gestational week of pregnancy.

Changes in Mom: Your uterus will begin rising past your hipbones any time now. You can feel it about three to four inches below your navel. During your appointments, your care provider will be measuring "fundal height" to make sure your baby is growing consistently and adequately. Fundal height is the distance from the top of the uterus (fundus) to the pubic bone.

Week 16

If you haven't already, you may begin to feel movement as the baby's bones harden. If you are somewhat overweight, have a thick uterus, and/or if this is your first pregnancy, you may not be feeling baby yet or feeling baby regularly. Don't panic! You will soon. The legs are now longer than the arms, and s/he is moving those arms and legs frequently, especially since there's still lots of room to move within the uterus.

Changes in Mom: Do you have a stuffy nose or nosebleeds? As mentioned before, your blood volume increases 40% - 50%. This affects your estrogen levels which in turn swells your nasal membranes. This increased blood volume also causes your heart to work harder to support your pregnancy. This isn't a problem for a healthy heart.

Week 17

This is a period of rapid growth as the fat begins to form underneath the baby's skin. Baby and placenta are about equal in size now. The tiny heart is pumping as much as 25 quarts of blood a day! The reflexes are probably in place now as the baby sucks, swallows and blinks.

Changes in Mom: Your uterus is about 1 1/2 to 2 inches below your belly button. The baby is going through a growth spurt and chances are, you may be gaining too! Average weight gain is between five and ten pounds at this point.

Week 18

Our little one is nearly half a pound now and very human looking. Pads are forming on the fingertips and toes, and the eyes are looking forward rather than out the sides of the head. Meconium, the baby's first bowel movement, is accumulating within the bowel. If your baby is a boy, his prostate gland is beginning to develop.

Changes in Mom: Feeling dizzy, lightheaded or faint are normal during pregnancy. These symptoms aren't harmful unless they occur frequently or severely. "Postural hypotension" is low blood pressure due to a change in position and happens frequently in pregnancy because your cardiovascular system doesn't react as fast.

Week 19

Along with the lanugo, vernix caseosa forms on your baby's skin. Vernix is a white cheesy substance that protects your baby's skin from its aquatic environment ~ imagine how your skin would look if you sat in water for nine months! The placenta continues to grow and nourish the baby.

Changes in Mom: You may be noticing several skin changes. These are hormone-related and will disappear after delivery. You may have the "mask of pregnancy" - blotchy patches on your forehead, cheeks, nose and chin. Itchy skin is also very common. Your skin may be dry and flaky in certain areas and many pregnant women develop rashes, particularly on the stretched skin. You can't prevent stretch marks but lotions or oil can ease the dryness and itching. Drinking lots of water and eating a healthy diet will go a long way in reducing dryness.

Week 20

We're halfway through the pregnancy, and the baby has as much sleep and awake time as a newborn. The scalp hair begins to grow. If your baby is a girl, her uterus is starting to develop.

Changes in Mom: Your uterus is at your navel now. You may experience some tenderness as your belly button becomes an "outtie" from the uterus pressing on it. The line between your navel (linea nigra) and pubic hair has darkened; it will fade after delivery.

Week 21

The rapid growth phase begins to slow down this week. The heart grows stronger this week, and the legs are reaching their relative proportions.

Changes in Mom: Over halfway there, and you're probably showing now. Your uterus is about 1/2 inch above your belly button. The average weight gain is between 10 and 15 pounds at this point. If you're eating a healthy diet, don't count pounds and calories too strictly. Emotionally, you're probably feeling more stable and comfortable.

Week 22

The baby is probably close to a pound and very thin but very developed. The eyelids and eyebrows are now formed, and the brain begins rapid growth. If your baby is a boy, his testes have begun their descent from the pelvis to the scrotum.

Changes in Mom: Your uterus is nearly an inch above your navel. You'll probably be gaining weight more steadily now as your baby continues to fill out. The extra weight may begin to take its toll on your back. Wear low heeled shoes (flat shoes can strain your back as much as high heeled shoes) and avoid sitting or standing for long periods of time. When you sit, use a footstool to raise your knees higher than your hips.

Week 23

Your baby weighs about a pound now! The body is becoming better proportioned each day, and the bones of the middle ear begin to harden. If born now, your baby has a chance for survival. Let's hope, however, that the baby stays put for several more weeks!

Changes in Mom: Your baby still has room to move around so you're probably feeling kicks, jabs, flips and flops. You may even see your abdomen move. Your uterus is about 1 1/2 inches above your belly button. If you're having some wild mood swings, don't fret. They're normal even if they don't feel normal. Try to be good to yourself when you're feeling blue.

Week 24

The baby gains about 6 ounces this week as the body begins to fill out. This weight is in muscle, bone mass and the growing organs and tissues. The weight could top 1 1/3 pounds by the end of the week.

Changes in Mom: Between weeks 24 and 28, your care provider may order a glucose tolerance test to determine if you have gestational diabetes. Your uterus is 1 1/2 to 2 inches above the navel.

Week 25

The structures of the spine - 33 rings, 150 joints and 1000 ligaments - begin to form. The blood vessels of the lungs are developing and the nostrils begin to open. Busy week!

Changes in Mom: You may be feeling like a "Soccer Mom" now that your uterus is the size of a soccer ball. Your growing uterus places pressure on your back and pelvis and may cause periodic shooting pains in your lower back and legs. When you experience this, rest, change your position, take a warm bath or apply ice to the sore area.

Week 26

Your baby could weigh about two pounds now and be around 9 inches long (crown of the head to the rump). As the blood vessels in the lungs began last week, the air sacs in the lungs begin this week. The lungs begin to secrete surfactant which covers the inner lining of the air sacs which then allows the lungs to expand normally during breathing.

Changes in Mom: Your uterus is about 2 1/2 inches above your belly button. If you feel your uterus suddenly tighten and then relax, don't panic. You're experiencing "Braxton Hicks" Contractions. These are normal, usually painless or feel similar to menstrual cramps and happen at irregular intervals. They are your body's way of practicing for the real thing and help to tone up your uterus for the tough job of labor.

Week 27

During this week, the brain continues its rapid growth, and the lungs continue to grow. Eyelids begin to open, and the retinas begin to form. The baby will grow over 1/2 inch this week and will be about 1 1/3 feet long (from crown of head to the toes or 9.6 inches from crown to rump)!

Changes in Mom: Congratulations! At the end of this week, you will have finished the second trimester already! You may be experiencing some shortness of breath. Your uterus is close to your rib cage now, and your lungs may not be able to fully expand. Don't worry though. Your baby isn't lacking oxygen and your circulatory system is actually working more efficiently thanks to those pregnancy hormones that have caused you so much discomfort.

Week 28

Our little miracle is growing and developing at an astonishing rate! Eyebrows and eyelashes are now present, and the hair on the head is growing. The eyelids open, and the eyes are completely formed. The body is getting plumper and rounder (weighs about 2 pounds) and is composed of around 2 to 3% body fat. Muscle tone is gradually improving. The lungs are capable of breathing air but if the baby is born now, it would struggle to properly breathe. Be sure to talk to your baby a lot because s/he can recognize your voice now!

Changes in Mom: Welcome to the third trimester ~ the period of leg cramps, hemorrhoids, varicose veins, itchy skin, aches and pains, swelling, heartburn, indigestion and . . . your baby's arrival!

Week 29

The baby's head is in proportion to the rest of the body. Fat continues to accumulate under the skin. The brain can control primitive breathing and body temperature control, and the eyes can move in the sockets. The baby is becoming sensitive to light, sound, taste and smell. Now, I wonder how experts know a baby can smell in utero?

Changes in Mom: Do you feel like you've been pregnant forever? Are those discomforts of pregnancy getting to you? This is the time when itchy skin, shortness of breath, hemorrhoids, leg cramps, heartburn and indigestion and achy muscles takes a toll. What do you do? Remember that these annoyances are temporary. Focus on the positive aspects of pregnancy!

Week 30

Our little one is nearly three pounds already and growing like a weed. The early lanugo is disappearing, the eyelids open and close, and the toenails are growing. The bone marrow is now responsible for red blood cell production.

Changes in Mom: The best sleeping position for a pregnant woman is on her left side. Your aorta and vena cava are slightly to the right of the center of your back, so laying/sleeping on your left side as much as possible ensures an unobstructed blood flow to your organs and extremities. You may be having some trouble sleeping now. Try one of the many maternity pillows or full-body pillows on the market. Sleeping in a recliner chair might also help, especially when the heartburn gets nasty.

Week 31

Growth begins to slow a teeny bit, and the brain goes through a period of rapid development. The only major organ left to fully develop is the lungs. If your baby is a boy, his testes begin to descend from the body cavity to the scrotum

Changes in Mom: Your abdomen may be aching frequently now as your uterus is stretching more and more. Your uterus is about 4 1/2 inches above your belly button with ten weeks to go. As your baby's bones harden and grow, your calcium needs are even greater. Be sure your diet is adequate in calcium, protein, iron and folic acid

Week 32

The baby is up to four pounds now and all five senses are functional. The toenails are completely formed and the hair on the head continues to grow.

Changes in Mom: You'll be gaining about a pound a week. Mild edema is normal but if you experience severe headache; seeing "spots" or "flashing lights" while at rest; sudden increase in swelling, such as over 2-3 days, especially of the face; abdominal pain; and nausea, vomiting, and feeling sick, contact your caregiver immediately. You could be developing pre-eclampsia which is characterized by swelling, high blood pressure and protein in the urine. It is a very serious complication of pregnancy.

Week 33

At this point, the amniotic fluid is at the highest level in the pregnancy. The amount will remain constant until delivery. Rapid brain growth has increased the baby's head size approximately 3/8 of an inch this week. Fat continues to accumulate which turns the baby's skin color from red to pink.

Changes in Mom: Over halfway there, and you're probably showing now. Your uterus is about 1/2 inch above your belly button. The average weight gain is between 10 and 15 pounds at this point. If you're eating a healthy diet, don't count pounds and calories too strictly. Emotionally, you're probably feeling more stable and comfortable.

Week 34

The baby responds as a newborn with its eyes open while awake and closed while sleeping. S/he is developing immunities to fight mild infection. Those sharp little fingernails are at the ends of the fingertips already, and you might need to clip them during the first few days after birth.

Changes in Mom: You've probably felt some Braxton Hicks contractions for the past several weeks but they may intensify now. They are usually painless and non-rhythmical. These are preparing your body for the real thing.

Week 35

The average sized baby is around five and a half pounds now! The fat accumulations plump up the arms and legs this week. The baby has gotten big enough to take up most of the uterus, and there's less room to move around. The testes have completed their descent in males.

Changes in Mom: Your care provider may begin regular checks of your cervix some time in the next few weeks for signs of effacement and dilation and to see what position your baby is in. Your baby cannot pass through a normally closed cervix. The process of labor is the stretching, thinning (effacement) and opening (dilation) of your cervix to allow the baby to pass through. Your cervix is fully dilated when the opening measures 10 centimeters.

Week 36

With four weeks to go, our baby is almost ready. S/he could drop into the birth canal at any time now. This week, the fat is dimpling on the elbows and knees as well as forming creases in the neck and wrists. The baby's gums are very rigid.

Changes in Mom: About a month to go ~ you'll probably be visiting your care provider once a week at this point. The average weight gain now is between 25 and 30 pounds. You should be consuming about 2400 calories per day. Make them count! Your body is working hard now and needs quality fuel.

Week 37

Average size is around 6.5 pounds now! The baby practices breathing movements preparing for life outside the womb. His/her grasp becomes firm, and s/he will turn toward light.

Changes in Mom: Vaginal discharge may be heavier now and will have more cervical mucous in it as your body prepares for labor. What position is your baby in? Is it head down or butt first? Whichever position your baby is in now is generally the way s/he will stay. If your baby is breech, you may need a cesarean or your care provider might recommend an external version in which your abdomen is manipulated in such a way that it turns head down. This is successful 60 to 70% of the time.

The baby could come at anytime. Is your hospital bag packed yet?

Week 38

The baby may be gaining an ounce a day now. His/her intestines are accumulating lots of meconium (baby's first bowel movement). The circumference of the head and the baby's abdomen are about the same size.

Changes in Mom: False labor contractions are irregular and can be very painful. These contractions may be felt in various parts of your body (back, lower abdomen, pelvis). True labor contractions start at the top of your uterus and then spread over the entire uterus, through your lower back and into the pelvis. True labor will become stronger and more painful and won't be alleviated by changing position.

Week 39

Most of the lanugo is gone as the baby prepares for its final womb days. The lungs are maturing and surfactant production is increasing. The baby can't move too much anymore as its womb space has become very crowded. The average size baby is over seven pounds at this point.

Changes in Mom: Are you feeling huge and clumsy? As the baby settles into your pelvis (lightening), your center of gravity shifts which may make you feel off-balance. The good news is, the uterus isn't pressing on your diaphragm so it's easier to breathe. The bad news is, your uterus is pushing on your bladder so you may be running to the bathroom every two minutes. Your uterus is 6 1/2 to 8 inches above your navel!

Week 40

The last week (or is it?). The average size newborn is 7.5 pounds and 20 inches long. At this point, most of the vernix is gone, 15% of the body is fat and the chest sticks out.

Changes in Mom: This may seem like a long week. Keep in mind that your baby's due date is only an estimate, and every baby is born in its own time. Be good to yourself and try to relax. You're not actually "post-due" until you hit 42 weeks. Just think about the poor elephant who is pregnant for 23 months! Your care provider may suggest induction if s/he feels that the pregnancy has continued long enough. Some moms welcome this while others want to avoid it. Be sure to make your wishes known.