Pregnancy week by week: A guide to pregnancy stages

Track your body's progress from first trimester all the way to the delivery date with this guide to pregnancy stages.
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By Lexi Dwyer

Congratulations, you're pregnant! There's no doubt this is one of the most monumental and memorable times of a woman's life, but it also comes with lots of physical, mental and emotional changes.

If you've found yourself Googling early pregnancy signs or "is morning sickness after 12 weeks normal?" (spoiler alert: totally!) or just wondering what to expect as pregnancy stages tick by week by week, check out this TODAY Parents pregnancy guide, which we put together with help from Dr. Myra J. Wick, an obstetrician/gynecologist at the Mayo Clinic, and her comprehensive, go-to guide for expecting moms, "Mayo Clinic Guide to a Healthy Pregnancy."

If you're newly pregnant, you can look forward to week 13, or the start of the second trimester, when early pregnancy symptoms subside. "We call this the honeymoon period, because most women feel well, they are over the nausea, but not so big they feel uncomfortable," Wick says. She adds, however, that "not everyone follows the books," and you should always report any concerns to your provider, paying special attention to things like spotting, heavy cramping and lack of fetal movement.

"Mayo Clinic Guide to a Healthy Pregnancy" by Dr. Myra J. Wick

Here's a guide to the pregnancy stages and pregnancy symptoms week by week.

First trimester pregnancy symptoms

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Pregnancy Symptoms Week 1

It's a bit of a mind-bender, but you aren't actually pregnant during what doctors call "week one" of pregnancy. Instead, week one starts on the first day of your last menstrual period before you conceived. When doctors speak about pregnancy, they're referring to the 40 weeks after the start of your last period, so your menstrual cycle is actually considered part of the process.

If you're trying to conceive, it makes sense to avoid smoking, alcohol and other drugs, and start taking a prenatal vitamin with at least 400 micrograms of folic acid, which can help reduce the risk of birth defects.

Pregnancy Symptoms Week 2

Since conception doesn't usually occur until two weeks from the start date of your last period, you still aren't pregnant during week two, but your body is getting prepped by producing hormones that help you release eggs, a process called ovulation. If you have unprotected sexual intercourse during this time, or attempt to get pregnant using a fertility procedure such as intrauterine insemination (IUI) or in vitro fertilization (IVF), your egg can be fertilized, forming a zygote.

If you're charting your basal body temperature, you will notice it rise slightly during ovulation, and if you become pregnant during this time, it will stay high for the duration of the pregnancy.

Pregnancy Symptoms Week 3

Let's say the first day of your last period was April 10 and you became pregnant thereafter; that would mean your baby was conceived around April 24, or during week 3. Certain pregnancy tests can detect the pregnancy hormone human chorionic gonadotropin (HCG) as early as 6 days after fertilization occurs, but false negatives may occur (meaning the test shows you aren't pregnant, but you actually are). To mitigate disappointment, some doctors advise waiting until you miss your next period to take a test.

When the fertilized egg travels through the fallopian tube and buries into the uterine lining, you may notice a small amount of light bleeding, spotting or vaginal discharge caused by implantation.

Pregnancy Symptoms Week 4

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By this point you may not have noticed any pregnancy symptoms, but things like nausea (also called morning sickness), fatigue, frequent urination and breast tenderness may start up around week four. You may also start to notice the skin around your nipples, called the areola, get darker and develop small bumps called tubercles (because nature is smart that way, their function is to secrete substances that help with breastfeeding later on). Some women also find that mood swings start around this time, and continue throughout pregnancy: They're caused by factors like fatigue, hormonal shifts and simply adjusting to the big news that parenthood is around the corner.

Pregnancy Symptoms Week 5

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Your body: If you haven't been noticing changes like nausea (which may or may not also include vomiting), frequent urination and exhaustion, most moms-to-be do experience this memorable triad of symptoms during the second month, which starts at week five. "In the first trimester it's normal to just find yourself being really tired and not feeling very well," says Wick.

Your little one: Although still teeny-tiny (about the size of an earring back), he or she is officially called an embryo by your medical team, and is working on developing what will become the brain, spinal cord and blood vessels.

Pregnancy Symptoms Week 6

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Your body: As hormones cause food to move more slowly through your body, you may continue to notice the digestive distress mentioned above, and possibly even constipation and heartburn. And despite the continuing fatigue, some moms find themselves also plagued by insomnia at various points during pregnancy, starting during the first trimester.

Your little one: It's a busy week for baby, who will triple in size and develop a regular heartbeat that you may be able to spot on an ultrasound.

Pregnancy Symptoms Week 7

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Your body: Along with nausea, exhaustion and moodiness, some women also experience dizziness and headaches throughout the first trimester, which may be caused by the expansion of veins and arteries as they work to produce more blood.

Your little one: Your kiddo, now one-third of an inch long, is starting to have more definition in the face as well as a visible umbilical cord.

Pregnancy Symptoms Week 8

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Your body: Your uterus, which started about the size of a closed fist, is now about as big as a grapefruit. Breast tenderness, nausea, and fatigue may be continuing. Although you should contact your provider as soon as you get a positive pregnancy test, many women have their first prenatal visit during week 8.

Your little one: Fingers and toes are starting to form as the hand and foot areas take shape.

Pregnancy Symptoms Week 9

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Your body: Looking ahead to week 10, for a smaller group of women with certain risk factors, doctors might suggest scheduling chorionic villus sampling (CVS), an optional test typically performed between 10 and 14 weeks that can detect chromosomal abnormalities like Down syndrome and inherited disorders like cystic fibrosis. This test is typically performed by inserting a catheter through the cervix to collect cells, and does pose a slight risk of miscarriage.

Your little one: Up until now, your developing embryo had a tail that gave him or her a tadpole-like look, but it's starting to shrink.

Pregnancy Symptoms Week 10

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Your body: Starting at week 10 you might opt to have non-invasive prenatal screening (NIPS), instead of a CVS. This is a simple blood test which can tell you the chances of developing certain chromosomal disorders. Both this test and a CVS can reveal your baby's sex if you wish to know it; otherwise, the 20-week ultrasound may be another opportunity to find out. At this point, some women may also notice slightly blurred vision and trouble tolerating contact lenses, which can be caused by the cornea beginning to thicken.

Your little one: Each of the vital organs has started to form, and tooth buds are starting to develop.

Pregnancy Symptoms Week 11

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Your body: You might notice that your hair and nails are growing a bit more quickly and that you've put on a few pounds (women may gain up to four pounds by the end of the first trimester).

Your little one: At week 11, healthcare providers officially promote your little bean from embryo to fetus. This is also when buds develop that will eventually become his or her external genitalia.

Pregnancy Symptoms Week 12

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Your body: Up until this point your uterus has fit inside your pelvis, but after this week it will start growing out of your pelvic cavity. You'll start to appear more pregnant, but there's a nice bonus: There will be less pressure on bladder.

Your little one: Fingernails and toenails are now present and the face is becoming more defined.

Second trimester pregnancy symptoms

Pregnancy Symptoms Week 13

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Your body: Raise a mocktail! For many women, symptoms of nausea and vomiting start to subside around week 13, or at least sometime during the next few weeks, although Wick says, "Some women may deal with nausea throughout their entire pregnancy." (Hopefully that's not you.) This week you may also notice a new symptom: Shortness of breath, which happens as a result of respiratory changes needed to support your growing baby.

Your little one: There are defined eyes and ears, but eyelids are now closed (as a protective measure) and will stay this way until about week 28.

Pregnancy Symptoms Week 14

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Your body: During both the first and second trimester, your blood pressure may decrease slightly from its pre-pregnancy number. This may cause dizzy spells, especially if you become overheated.

Your little one: Fun fact: This is the time when your little fetus begins producing hormones. Also, the prostate gland (in boys) and ovaries (in girls) are developing.

Pregnancy Symptoms Week 15

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Your body: Maybe you've been spared the oh-so-fun digestive symptoms of heartburn and constipation, but women often tend to notice them around now. Know that the slowdown of your digestion at least has a greater purpose, which is to help deliver important nutrients to your growing babe. Amniocentesis, a procedure where fluid is withdrawn with a needle to check for things like genetic disorders, is usually performed sometime between weeks 15 and 20.

Your little one: Thanks to the continued growth of muscles, this week is when baby will start being able to make a fist.

Pregnancy Symptoms Week 16

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Your body: Your uterus is movin' on up, but this can cause an unwelcome side effect: You may start to feel off-balance, and continue to experience this as your shape changes.

Your little one: Your wee one's eyes are sensitive to light. Baby hiccups could be starting, although you likely won't feel them yet.

Pregnancy Symptoms Week 17

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Your body: Around week 17, you may start to feel baby's fluttery little movements; some women mistake them for gas or hunger at first. (Women who've been pregnant before tend to feel them earlier.) But definitely within the next few weeks you'll become aware of them. You'll continue to experience symptoms that are the hallmarks of pregnancy: Slow digestion, frequent urination and increasing breast size.

Your little one: Whether or not he or she will end up loving gymnastics, your baby is doing flips and rolls by this point, and still has space to move around quite a bit.

Pregnancy Symptoms Week 18

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Your body: Make sure you've got a good moisturizer handy: As your belly grows and stretches, it may begin to itch. Some women experience darkening of the skin and changes in moles (if any look significantly larger or different, check in with a dermatologist).

Your little one: Baby's bones are getting harder and he or she can now hear noises like your heartbeat and even loud sounds that take place outside the womb.

Pregnancy Symptoms Week 19

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Your body: Right around now is when you may notice a stabbing sensation in your groin or on one side—this is coming from the round ligament, which grows and stretches to support your uterus during pregnancy. Sudden movements may bring it on, so try to change positions slowly (like when you're getting out of bed).

Your little one: This week the vernix appears: It's a slippery, cheese-like coating on baby's body that helps protect skin. Your baby can now produce urine, which is sterile and gets excreted into the surrounding amniotic waters.

Pregnancy Symptoms Week 20

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Your body: You're at the halfway point! Pat yourself on the back, or, even better, treat yourself to a prenatal massage. At this point women may start to notice low back pain, especially if they were prone to it before they were pregnant. By now you may have gained around 10 pounds total, although it can vary from woman to woman.

Your little one: The skin is developing its distinct layers and although it's the middle mark, baby still likely weighs less than a pound—probably about 10 to 14 ounces. If he or she is in the right position, you can usually learn the sex at your 20-week ultrasound, since the external genitalia have developed enough to be visible.

Pregnancy Symptoms Week 21

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Your body: You may notice that your breasts are beginning to leak colostrum, which is a watery, yellowish fluid that appears before your regular milk supply is established; if you choose to breastfeed, it will be baby's first food.

Something your doctor will monitor you for after 20 weeks is preeclampsia, a condition that causes high blood pressure during pregnancy. "Although many women experience swelling throughout pregnancy, if you have swelling that's accompanied by headache, visual changes, nausea or pain in the right upper quadrant of your abdomen, definitely let your doctor know right away, as these can indicate preeclampsia," says Wick.

Your little one: Helped by the liver and spleen, your baby's bone marrow is now able to make blood cells.

Pregnancy Symptoms Week 22

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Your body: This week you might start feeling irregular Braxton-Hicks contractions in your abdominal area, which help your body prepare for labor. (They're sometimes called "false labor.") To distinguish them from true contractions, which radiate around both sides of your body, try lying down, changing positions or drinking water. These things will cause Braxton-Hicks to subside, unlike true, regular contractions that grow stronger and indicate labor is approaching.

Your little one: The senses of taste and touch, as well as the reproductive system, are all becoming more developed around this time.

Pregnancy Symptoms Week 23

Your body: Pregnant women sometimes find that their sex drive is improved during the second trimester—if this is you, take advantage!

Your little one: Around this time is when the development of the lungs really kicks into high gear.

Pregnancy Symptoms Week 24

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Your body: During the second trimester, your joints may start to feel softer due to hormone changes that are slowly preparing your body for childbirth. Your lower spine also starts to curve backwards to accommodate your changing shape. These transformations may lead to back and hip pain; both massage and prenatal yoga may help alleviate some discomfort.

Your little one: Babies born on or after week 24 have a greater than 50-50 chance of survival, thanks to today's innovative neonatal care, but are still very likely to have complications if delivered this early.

Pregnancy Symptoms Week 25

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Your body: If your blood pressure dropped during your first and second trimesters, you may see it start to return to pre-pregnancy levels.

Your little one: Baby's hands are now fully formed, can be used to explore the womb environment or their own body, although the movements aren't purposeful yet.

Pregnancy Symptoms Week 26

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Your body: Thanks to the hormone relaxin, which is produced during pregnancy, the muscles that hold up your pelvic bones will continue to soften to prepare for giving birth. It won't necessarily feel "relaxing" though: Many women experience pain in the front of the pelvic area. If it's truly bothersome, consider making an appointment with a physical therapist who specializes in prenatal and postnatal conditions.

Your little one: Footprints, which make a fun hospital souvenir, as well as fingerprints, are now present on your baby, who weighs about 1 ½ pounds.

Pregnancy Symptoms Week 27

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Your body: You've likely had vaginal discharge throughout your pregnancy, and you may see it pick up around now. As long as it's clear or white and odorless, it's not a cause for alarm, but see your provider if you suspect a yeast infection, which, along with urinary tract infections, you're more prone to during pregnancy.

Your little one: The lungs are getting close to being fully developed, and although it's tough to hear through all the amniotic fluid, your little one could possibly recognize the sound of Mom's voice this week.

Third trimester pregnancy symptoms

Pregnancy Symptoms Week 28

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Your body: Welcome to the third and final trimester of pregnancy. After 28 weeks, doctors recommend women start tracking kick counts. "You want to ideally feel 10 movements in two hours, but most babies move enough so their mothers have a sense for the pattern, and if it changes or you aren't feel baby move at all, definitely contact your provider," says Wick.

Your little one: Around this time is when baby's eyes, which were previously sealed shut, start opening and closing.

Pregnancy Symptoms Week 29

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Your body: Another change that may happen during either this trimester or the second: If you have an innie belly button, it could pop out and turn into an outie. If clothing irritates it, consider covering it with a bandage and don't worry about the change being permanent, it will likely flip back after delivery.

Your little one: This week is right in the middle of baby's most active period, which is usually between 27 and 32 weeks, because they still have room to move around.

Pregnancy Symptoms Week 30

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Your body: Another unappealing symptom of late pregnancy: Urine leakage, especially when you cough, sneeze or laugh. Performing exercises to strengthen your core and pelvic floor (such as kegels) may help, but you're still experiencing this after delivery, make an appointment with a physical therapist who specializes in pelvic floor therapy.

Your little one: Time to pack on the pounds, kid: Starting now until delivery, fetal weight gain will be about a half-pound each week.

Pregnancy Symptoms Week 31

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Your body: Thanks to the hormonal changes, you are likely rocking a lush, awesome mane right now, since hair tends to grow more quickly and fall out less frequently when you're pregnant. You will lose the extra hair after delivery, though, so don't get too attached.

Your little one: The reproductive system is continuing to take shape, as are the lungs, though they still aren't fully ready for life outside the womb (a baby born this early would need to spend time in the neonatal intensive care unit, or NICU).

Pregnancy Symptoms Week 32

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Your body: During these last few weeks you've probably been continuing to experience pregnancy symptoms such as heartburn, constipation (and possibly hemorrhoids as a result) and swollen breasts (that may or may not leak colostrum). Keep your eye on the prize: That adorable baby who's on the way.

Your little one: Your baby is still moving around, but the jabs and punches may seem to have lost their oomph, since he or she is getting increasingly crowded. At this point, baby weighs around 4 pounds and the risk of serious post-delivery complications drops quite a bit, so parents tend to breathe a sigh of relief.

Pregnancy Symptoms Week 33

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Your body: During the third trimester, your ever-softening joints will likely continue to bug you. "Around this time we tend to see joint discomfort in hips, back and nerve pain and just a lot of pelvic discomfort," says Wick. Your muscles also may simply be sore and tired from carrying increased weight, so try to rest frequently if possible.

Your little one: Lots of growth and change takes place after week 33. One cool thing that's now happening: The pupils can dilate and constrict in response to light.

Pregnancy Symptoms Week 34

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Your body: Late in pregnancy, women may feel occasional sharp pain in the vaginal area as well as general pelvic pressure, but if at any point you're having symptoms such as unrelenting abdominal pain or bleeding, contact your doctor as you may be experiencing a problem with your placenta. "Pelvic pressure is usually normal, but if it's persistent, you're having discharge with it, sometimes it can be a sign of preterm labor, so check in with your doctor," says Wick.

Your little one: This kid now weighs anywhere from 4 ½ to 6 pounds—things are getting real!

Pregnancy Symptoms Week 35

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Your body: If you haven't experienced them already, you will likely have Braxton-Hicks contractions this month.

Your little one: Conditions are cramped but your small one is still wiggling around, so keep tracking those movements.

Pregnancy Symptoms Week 36

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Your body: Leg, ankle and foot swelling are common around this time, as are varicose veins, which may disappear after childbirth. Invest in comfy shoes and hit your partner up for a nightly foot massage.

Your little one: The facial muscles needed for sucking are ready to go and your child might weigh as much as 7 pounds. By this point, most babies have settled into the head-down orientation that's ideal for delivering vaginally.

Pregnancy Symptoms Week 37

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Your body: Maybe it's nature's way of getting you ready to deliver your baby, but women find themselves pretty uncomfortable during the third trimester, especially towards the end. "By this point there is a lot of pressure on the bladder, you can feel very full, it can be hard to sleep at night, and even the kicking can be uncomfortable if baby is up against the ribs," says Wick.

Your little one: Your bambino's rate of weight gain slows a bit this week, and at the end of this week, your baby will be considered "early term" in medical lingo.

Pregnancy Symptoms Week 38

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Your body: Your uterus now extends nearly all the way up to the base of your rib cage. Need proof that pregnant women are true superheroes? Consider the fact that during pregnancy, the uterus grows about 500 times in size.

Your little one: Although we think of it as automatic, by now your child has an important set of skills: Breathing, eating and digesting, as well as keeping a normal cardiac rate.

Pregnancy Symptoms Week 39

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Your body: During these last few weeks, your head-down baby may descend further into your pelvis, thus making breathing feel easier (this is more common for first-time moms). "Lightening," as it's called, doesn't necessarily mean labor is imminent.

Your little one: Many babies the proper amount of fat under his or her skin to help maintain a stable body temperature, although even when an infant is healthy and full-term, you still need to be cautious that they don't become too warm or cold.

Pregnancy Symptoms Week 40

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Your body: Your due date is this week! Get ready for a flurry of texts and emails from friends checking in, even though only a tiny percentage of women (4%) deliver on the due date. If you haven't gone into labor yet, you'll continue with your prenatal visits and your provider will monitor the health of you and your baby. If you started your pregnancy at a healthy weight, you may have gained anywhere from 25 to 35 pounds by this point.

Your little one: Baby is now considered full-term and although the average weight is 7 ½ to 8 pounds, there is a wide size range for a healthy infant.

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