Week - 2

Here's what's happening during Week 2 of your pregnancy

Ovulation occurs; ideally, sperm will already be lying (er, swimming) in womb. Though some women swear that they were aware of the moment of conception, most are oblivious. The radical hormonal changes of the first trimester don't kick in until implantation, which happens between three to five days after conception. If you've been trying to get pregnant, you may be waiting on the edge of your seat until a test can confirm your pregnancy. If you weren't trying, you may be on the edge of your seat for the same reason.

Week - 3

Here's what's happening during Week 3 of your pregnancy

Fertilization occurs in one of the fallopian tubes. Cell division begins at breakneck speed.

Though it's very early in your pregnancy, things are definitely happening! Once the "winning" sperm (one of 200 million or so contenders) has penetrated your egg, the egg shuts down, admitting no more sperm. Two sets of cell nuclei fuse together inside the egg, assigning your baby—now called a zygote—a gender, eye and hair color and more than 200 other genetically determined characteristics.

Week - 4

Here's what's happening during Week 4 of your pregnancy

The fertilized egg (known as a zygote) implants in the wall of the uterus; the placenta and umbilical cord begin to form.

The fertilized egg burrowing into you uterus can make you shed a few spots of blood. Any pregnancy symptoms you have will be barely, if at all, noticeable. If you're very sensitive, you may notice feelings of fatigue, queasiness, bloating, and breast tenderness, and changes in your skin and hair. If you take a super-sensitive test, such as a blood test at your doctor's office, it's possible to get a positive result a week after conception. If you test at home this early, know that it's possible to get a false negative at this stage.

Week - 5

Here's what's happening during Week 5 of your pregnancy

The gastrointestinal tract, spinal cord, heart, brain, blood and blood vessels begin to form. The embryo is 1/16 to 1/8 inch long "crown to rump" (the measurement that's used until week 13).

Your baby transforms into a bundle of cells organized in a C-shape with a top, bottom, front, and back. A groove has developed on the embryo's back, which will seal and develop into the neural tube (which later will become the spinal cord). At this point, the tube already has a wider, flatter top that will grow into your baby's brain. A bulge has developed in the center of the embryo, which will soon become a tiny U-shaped tube which will form the heart. Your embryo is encased in protective membranes and attached to a yolk sac, which manufactures the embryo's unique blood cells.

Week - 6

Here's what's happening during Week 6 of your pregnancy

The heart begins to pump blood, and the neural tube that will become the spine closes (which is why taking folic acid early is essential).

The embryo takes on a C-shape; arm and leg buds begin to form; and the skin is translucent. Length: about 1/4 inch. Fetus fact: The heart will beat 54 million times before birth!

Week - 7

Here's what's happening during Week 7 of your pregnancy

The head is about 1/3 the size of the entire embryo. The brain and face are developing rapidly, and nostrils and lenses of the eyes begin to form. Arm buds become paddle-shaped; hands begin to form. Length: about 1/3 inch.

The mucus on your cervix is thickening, forming a plug that will keep your uterus sealed until you give birth. You may not notice any difference in your body, or you may notice that you're beginning to lose your waistline.

Week - 8

Here's what's happening during Week 8 of your pregnancy

Brainwave activity starts. Fingers and toes begin to form and are webbed. Lungs, ears, eyes, upper lip and nose start to form. The body is beginning to straighten, and subtle movements begin. Length: about 1/2 inch.

If you're going to get pregnancy-related nausea (aka morning sickness), it probably will have kicked in by now. Researchers don't know its exact cause, but it's certainly related to your surging hormones.

Week - 9

Here's what's happening during Week 9 of your pregnancy

The heart is almost completely developed. Eyelids are forming, as are hair follicles and nipples; the embryo can hiccup now. Fingers and toes are no longer webbed. The arms develop bones, and the hands begin to touch the face. The legs start to move. Length: about 3/4 inch.

Week - 10

Here's what's happening during Week 10 of your pregnancy

The developing baby is now called a fetus. The eyelids begin to fuse to protect the eyes. The fetus begins doing occasional breathing movements, although it gets oxygen through the umbilical cord. The skin becomes less translucent, and genitals begin to form. Length: almost 1 ¼ inches.

Week - 11

Here's what's happening during Week 11 of your pregnancy

Nearly all the organs and body structures are formed and beginning to function. Genitals begin to take on either male or female form. The head makes up about half of the fetus's body. Length: about 2 inches. Fetus fact: The fetus can sigh, stretch, move its head and suck its thumb.

Week - 12

Here's what's happening during Week 12 of your pregnancy

The face begins to look more human. Length: 3 inches (head to heel, the measurement from now on).

She may weigh as much as half an ounce. This begins the age when the fetus starts to look really cut in those womb pictures. If you had a womb camera, you'd be able to see your baby's proportions changing, with the growth of the head slowing down to let the rest of the body catch up. Arms, legs, and fingers are also growing out and tapering to look more like a newborn's, and your baby's posture becomes less curled and more upright.

Week - 13

Here's what's happening during Week 13 of your pregnancy

The nose and lips are completely formed, and the fetus begins to produce and excrete urine.

Your baby is 2 1/2 to 3 inches long, the size of a medium goldfish. She weighs about one ounce. Your baby is shorter than a finger, but her face is already showing individual features and characteristics. Your baby spends her time in your womb flexing her new and developing muscles and joints. Bouts of prenatal hiccups are strengthening your baby's diaphragm, which is preparing her respiratory system for breathing. Less glamorous but highly necessary organ systems for making hormones, absorbing nutrients, and filtering waste are also in place this week. The pancreas, gall bladder, and thyroid have developed, the kidneys can make urine, and her bone marrow is making white blood cells to help fight infection after she's born.

Week - 14

Here's what's happening during Week 14 of your pregnancy

Your baby is about 4 to 4 ½ inches and about 1 ¾ of an ounce. If you could see your baby's face, you might be able to see her wince and grimace, because her facial muscles are developing and flexing. All of her tiny organs, nerves, and muscles are starting to function. The intestines have moved farther into the baby's body; her liver begins to secrete bile, which will later aid in the digestion of fats; and her pancreas begins to produce insulin, a hormone which turns sugar into energy.

Week - 15

Here's what's happening during Week 15 of your pregnancy

The nose, lips and taste buds are formed. The head is covered by a fine, soft hair called lanugo. Length: about 5 inches; weight: about 2 ounces. Fetus fact: Starting now, female fetuses show mouth movements much more often than males.

Week - 16

Here's what's happening during Week 16 of your pregnancy

Your baby weighs about 2.8 ounces (79 grams) and is about 4 1/2 inches from crown to rump—roughly the size of a small gerbil. At any time, you will begin to feel fetal movement as your baby's bones harden, and she starts a big growth spurt. Your baby has plenty of room: At this point, she could fit in the palm of your hand. This is a great time to be a fetus. At any given time, she might be playing with the umbilical cord (which she's now able to grasp), putting her thumb in her mouth, or kicking at the amniotic sac.

Week - 17

Here's what's happening during Week 17 of your pregnancy

Your baby is about as wide as your palm, about six inches tall, and weighs about four ounces—about as much as a bar of soap. She now weighs more than your placenta. Your baby is now covered with a downy layer of lanugo, which swirls in fingerprint-like formation over her whole body. Her skin is still thin. Brown fat, a special type of fat that plays a role in body heat generation, is being deposited. In the next few weeks, your baby's eyes will begin to move beneath their fused lids in a side-to-side sweeping motion.

Week - 18

Here's what's happening during Week 18 of your pregnancy

Fat is being deposited throughout the body. Teeth have started to form. The fetus begins to hear sounds in your body (such as your heart beating) and may even startle at loud noises. Length: about 8 inches; weight: 6 ounces

There's still plenty of room in your uterus, so your fetus can be quite active with her new muscles. She may change positions frequently, cross her legs, recline, suck her thumb, and turn somersaults. Her retinas have become light sensitive, and your baby may be able to detect a glow if you shine bright lights at your belly (even though her eyelids are sealed).

Week - 19

Here's what's happening during Week 19 of your pregnancy

Your baby weighs about 8 1/2 ounces, and measures about 6 inches long.

If the baby is a girl, early ovaries contain follicles with forming eggs. Soon, half of the genetic material for your potential future grandchildren will be formed. Pictures of babies at this age show them touching the membrane of the amniotic sac, touching their own faces, reaching for the umbilical cord, pedaling their legs, and sucking their thumbs.

Week - 20

Here's what's happening during Week 20 of your pregnancy

A white, creamy substance called vernix caseosa protects the skin from its aqueous environment. Sweat glands form. Length: about 10 inches; weight: 9 ounces. Fetus fact: Starting now, immunities are being transferred from you to the fetus.

Week - 21

Here's what's happening during Week 21 of your pregnancy

Your baby now weighs about three-quarters of a pound and is approximately 10 1/2 inches long.

Your baby has begun her main project for the rest of your pregnancy: putting on weight. She regularly drinks amniotic fluid for hydration and nutrition, urinates in the fluid and breathes in and out (fortunately, the fluid pool refreshes itself every three hours). Her eyebrows and eyelids are fully developed. Taste buds are forming on her tongue. Her eyelids are still sealed, but her eyes are active.

Week - 22

Here's what's happening during Week 22 of your pregnancy

The brain has entered a phase of extremely rapid growth. Length: about 11 inches; weight: just under 1 pound.

She is entering her fifth month of existence. Her fingernails are almost fully grown, and her organ systems are becoming more functional and specialized. She has a distinct pair of lips, and her first canines and molars are developing below her gum line. She looks like a miniature newborn. Blood is traveling through the umbilical cord at four miles an hour, fueling her growth with oxygen and nutrients.

Week - 23

Here's what's happening during Week 23 of your pregnancy

The testicles begin to descend into the groin from the abdomen; the uterus and ovaries have developed. Body proportions are similar to a newborn's, though the fetus is still thin. The eyes are formed but lack pigmentation. Length: about 11 1∕2 inches; weight: about 1 pound.

Week - 24

Here's what's happening during Week 24 of your pregnancy

The fetus develops waking/sleeping patterns. Real hair (not lanugo) begins to grow on the head. Length: about 12 inches; weight: 1 ¼ pounds. Fetus fact: If born now, your baby would have about a 50 percent chance of surviving.

Your baby's skin becomes less translucent as pigment is deposited, and it looks wrinkly because her body is making her skin more quickly than it makes the fat to pad underneath it. Your baby's unique hand- and footprints are forming. You may feel jumps as she has bouts of hiccups. In fact, it may seem like the baby is in perpetual motion. Some babies now kick in response to sounds and touch from outside the womb. Encourage your partner to talk to the baby, and see if she kicks in response!

Week - 25

Here's what's happening during Week 25 of your pregnancy

Your baby weighs 1 1/2 pounds and is a little more than 13 inches long, about the size of a small bag of sugar. In the last third of pregnancy, she'll double and triple her weight.

Your dexterous baby can touch and hold her feet and make a fist. Your partner may be able to hear her heartbeat by pressing his ear against your belly. Your baby has a regular sleep schedule now and active and inactive periods. You may or may not be able to discern what those periods are. Her nostrils, which have been plugged, open up.

Week - 26

Here's what's happening during Week 26 of your pregnancy

The eyelids separate and the eyes are starting to open. Lungs are beginning to develop surfactant, which allows them to inflate. The fetus begins to sleep for longer periods, often when you do. Length: 14 inches; weight: almost 2 pounds.

This week marks a major milestone in your baby's hearing and sight. Your baby's hearing system (cochlea and peripheral sensory end organs), which began fine development during week eighteen, is now completely formed, and over the next few weeks, she'll become increasingly sensitive to sound. In about a month, you'll feel her jump if she hears a sudden loud noise. Sound passes easily into your uterus, which helps her ears develop. Her eyes are almost fully formed. Did you know that all babies have blue eyes in the womb, no matter what their genetic inheritance is? A baby's eyes don't get their final color until a few months after they are born. The air sacs of the lungs, called alveoli, will be developed by the end of this week and will begin to secrete a substance called surfactant that keeps the lung tissue from sticking together.

Week - 27

Here's what's happening during Week 27 of your pregnancy

Your baby weighs about two pounds and is about 14 to 15 inches long, about the size of a small pot roast.

If your baby were born now, he would have an excellent chance (85 percent) of surviving. He still isn't fully formed and would probably not be able to breath by himself. He would need to stay in an incubator to keep his body temperature regulated, and he would have a weak liver and immune system. (Fact: Babies have more taste buds at birth than they will have later in life. Newborns can sniff out and tell the difference between their mother's milk and someone else's.)

Week - 28

Here's what's happening during Week 28 of your pregnancy

The fetus can taste and smell, and the eyes can produce tears. The bones are almost fully developed though still soft. Weight gain is rapid from now on. Length: about 15 inches; weight: more than 2 1/2 pounds. Fetus fact: The brain will increase 400 percent to 500 percent in weight between now and delivery.

Your baby's main job right now is to put the finishing touches on major organ systems, such as her brain, lungs, and liver. As you can probably tell, she's also working on gaining layers of fat. Her body fat is about 2 to 3 percent. Her sucking and swallowing skills are improving.

Week - 29

Here's what's happening during Week 29 of your pregnancy

Your baby is about two and a half pounds and would be between fifteen and seventeen inches tall if she could stand.

Your baby's adrenal glands are producing a chemical which will be made into estriol (a form of estrogen) by the placenta. This estriol is thought to stimulate the production of prolactin by your body, and the prolactin makes you produce milk. So even if your baby comes early, you'll still be able to breastfeed.

Each passing week improves the likelihood that your baby will be born strong and healthy. Her brain can detect rhythmic breathing and control body temperature, so she's less likely to need breathing assistance should she be born early. She's growing eyelashes, adding fat, and developing her brain. Because of brain wave activity, researchers have speculated that babies can even dream at this time!

Week - 30

Here's what's happening during Week 30 of your pregnancy

Your baby's length is about 16 inches—about as long as a laptop computer—and she measures almost 11 inches from crown to rump. She weighs approximately 2 1/2 to 3 pounds.

From now until delivery, every baby will gain weight at a more individual rate. Your baby has doubled in height over the past six weeks, and from now until delivery, she'll gain only a few more inches in length. Don't worry if she's in a strange position (what your care provider might call a "transverse lie"). There's still plenty of time for her to get settled into the head-down (cephalic) position for birth.

She's floating in about 1 1/2 pints of amniotic fluid and has some room to move. Your baby's most important organ, her brain, continues to develop at a rapid pace. Her eyes are able to track light, and some researchers have theorized that exposing your belly to light may stimulate development. Try moving the beam of a flashlight slowly over your belly in a dim room, and see if she reacts.

Week - 31

Here's what's happening during Week 31 of your pregnancy

Your baby weighs between 2 1/2 and 3 1/2 pounds. She continues to gain weight at a faster pace than she lengthens, which will give her those cute chubby cheeks. She's about fourteen to sixteen inches tall, although individual growth rates vary.

Your baby begins to run out of room as she puts on weight. You should feel about ten kicks an hour. Some care providers suggest keeping a "kick chart" by writing down how many kicks you feel in an hour, so that you are aware if there's a decrease in activity. Other care providers may advise that as long as it feels like the baby's active, there's no need to keep notes. If you do sense a decrease in activity, try drinking a large glass of juice. If that doesn't make the baby energized, or makes her less energized than she usually would be, call your care provider.

Week - 32

Here's what's happening during Week 32 of your pregnancy

The fetus practices breathing motions in preparation for birth. All five senses are developed, and REM (dream-cycle) sleep is beginning. Lanugo begins to disappear. Length: about 17 inches; weight: about 4 pounds. Fetus fact: If your baby were born now, he would have an excellent chance of surviving without life-threatening complications.

Week - 33

Here's what's happening during Week 33 of your pregnancy

Your baby's crown-to-rump length is about 17 inches. She weighs about 4 1/2 pounds and gains about eight ounces every week.

Your baby has probably moved to the head-down position and may descend into your pelvis at any time in the next six weeks and begin to press into your cervix. This position not only prepares her for birth but allows blood to flow to her developing brain. The dark quiet of your womb is perfect for this activity. Right now, your baby is also in the process of receiving your antibodies. If she were born right now, her immune system would be immature, and extra care would need to be taken to keep her in a sterile environment.

Week - 34

Here's what's happening during Week 34 of your pregnancy

The fetus is taking deep breaths. The eyes can blink and are open when it's awake and closed when asleep, and the pupils dilate and constrict in reaction to light. Length: about 18 inches; weight: about 5 pounds.

Your baby's brain is forming trillions of connections, making it possible for her to learn in the womb. All of this brain development may be the reason that your baby sleeps frequently at this stage. She may even be dreaming—her eyes dart around rapidly just as an adult's might in REM sleep. Your child's development is in no way complete at birth. In the first year after birth, a baby's brain triples in size and becomes three-quarters of its adult size.

Week - 35

Here's what's happening during Week 35 of your pregnancy

At more than five pounds and between sixteen and twenty inches, your baby is becoming more ready for birth with every passing hour. She's the size of a small roasting chicken.

Her nervous system and immune system are still maturing, and she's adding the fat that she'll need to regulate her body temperature. But, everything else, from her toenails to the hair on her head, is fully formed. If she were born now, she'd have more than a ninety-nine percent chance of surviving.

Week - 36

Here's what's happening during Week 36 of your pregnancy

With one month to go, your baby weighs about six pounds and is fattening. Her full length from crown to feet is about 20 1/2 inches.

Has your baby's movement slowed down? If so, you shouldn't worry. Five to ten percent of all mothers report that babies start to slow down as they grow larger and get more cramped for space. Still, you should be able to feel your baby move more than ten times a day. If you're concerned, try drinking a sweet beverage, such as orange juice, and then lying on your side for a while. Most babies will wake up and start to move. If you're still concerned, contact your healthcare provider.

Week - 37

Here's what's happening during Week 37 of your pregnancy

Your baby is now 20-21 inches or so and weighs about 6-7 pounds; he looks very much like a newborn. In the vast majority of pregnancies, the fetus begins to move into delivery position.

Your baby is practicing her breathing, but she has increasingly less space to practice stretching and kicking. Your baby' intestines are also building up meconium, a greenish-black substance made of baby by-products such as dead cells, shed lanugo, and amniotic fluid. It'll become your little darling's first bowel movement, hopefully after she is out of the womb.

Week - 38

Here's what's happening during Week 38 of your pregnancy

The average newborn has a length of 21 1/2 inches and weighs 7 1/2 pounds. She is fully developed, though still adding connections between neurons in the brain (this continues well after birth). Her nails have been growing and now reach to the ends of her fingers and toes. Her movements are quite restricted by her close quarters.

Week - 39

Here's what's happening during Week 39 of your pregnancy

You're in the home stretch! After nine months of growth and development, your baby is ready to be born, or nearly so. At week 39, your baby is fully developed and anywhere from 17-23 inches long and weighs 6-10 pounds. Don't be frightened if your OB-GYN says your baby is large: It's extremely difficult to judge a baby's weight accurately from the outside.

Your baby is adding neural connections and growing hair and still gaining weight. Researchers have theorized that when babies are ready to be born, they send a chemical signal of androgens to the placenta, which increases the production of estrogen and leads to labor. If so, it's proof of the old saying that "only a baby knows when it's ready to be born."

Week - 40

Here's what's happening during Week 40 of your pregnancy

If your due date has come and gone, your pregnancy is officially post-date. If you're still pregnant two weeks from now, then your pregnancy will be post-term. Anywhere from three to twelve percent of pregnant women may go post-term. The good news is that the baby is going to come out at some point—the bad news is that it may be as much as two weeks from now.

In the meantime, your care provider will check your dilation (how open your cervix is, if at all) and effacement (how thick your cervix is), to try to predict when labor will begin. If you hit forty-two weeks, your doctor will assess your health with a non-stress test and may use ultrasound to see if your baby has enough amniotic fluid. If your baby seems fine, you and your care provider can discuss when to schedule induction of labor. No matter what, one way or another, somehow, that baby's getting out!

Week - 41

Here's what you need to know about giving birth

You successfully made a baby (that was the fun part!) and by now you have this whole pregnancy thing down. Labor, though, is fast approaching a fact you may simultaneously dread and cheer. But even if this is Baby, you can approach L&D with the cool of a pro by being as informed as possible. From how to manage pain for a natural birth to what an epidural is really like, we have everything you need to know about labor and delivery right here.

Week - 42

Baby's here, now what?

You made it through to the other side and are now cradling a real, live human baby. It's is a joyous, emotional and, yes, sometimes terrifying time. Whether this is your first or last, don't worry we've got your back. From baby care, to health and development and feeding, we have all the answers to your newborn questions right here. You got this, Mama!