Pregnancy Week by Week

Curious about what is going on with your baby? These illustrations can take you on a wonderful journey from the tiny mass of cells to the fully developed baby you will have at the end of 40 weeks. Of course, each baby develops differently, but this is a pretty good representation of what to expect from your growing bundle of joy, so here we present you with the "pregnancy week by week".

Pregnancy Week by Week--First Trimester

Timeline

Descriptions

1 week

1 week pregnancy

At this point, you’re not actually pregnant yet–strange but true. Doctors calculate your pregnancy date by the first day of your last period, and many women don’t get pregnant until ovulation happens, about a week or so after that. But your body is preparing for a baby by releasing an egg very soon, and hopefully the magic will happen!

2 weeks

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You’re ovulating about this time, which means that you can become pregnant. Make sure that you are as healthy as can be at this point, because every day counts! Once you conceive and your baby begins growing, you might be amazed at how fast things happen.

3 weeks

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Now you’re pregnant! Your body is changing immediately to accommodate your new little one. Deep inside you, many things are happening. Your baby is known as a blastocyst, and it is rapidly dividing cells. It is burrowed into the rich uterine lining. Your body is busy producing the cells that will become the placenta, the yolk sac, the amniotic sac and the embryo itself. In fact, you might notice a bit of spotting as the blastocyst implants in the uterine lining. This is normal and means that everything is about to truly begin!

4 weeks

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Now your baby is the size of a poppy seed, and still dividing cells. In fact, the major structures of the body are about to develop. The neural tube, which will eventually create the spinal cord and brain, are the top layer of cells. The middle layer of cells will turn into the heart and circulatory system. The lower layer will be the lungs, liver and other organs.

5 weeks

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Your baby is a centimeter long, looks very much like a tadpole and has a tiny heart that is already beating. The neural tube will close this week, and the major organs will begin their serious development. The arms and legs are beginning to sprout, and small folds are beginning to form around where the face and jaw will be.

6 weeks

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At this point, your baby is the size of a lentil, with a tiny body and an oversized head. Facial features are already starting to form, so is the muscle and tissue that will make up the limbs. The brain is forming, so is the pituitary gland, which releases hormones that help boost growth even more. The heart has divided into left and right chambers.

7 weeks

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The fingers and toes are here! And so is the liver, which is churning out lots of red blood cells to help the baby grow. The teeth are forming, and so is the skin. Tiny blood vessels are visible now, and the heart has grown even more. Your baby is now the size of a chickpea and is moving around a bit as it grows.

8 weeks

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Muscles, nerves and organs are beginning to function already, and your baby can now bend his hands at the wrist. The feet are more distinct. The brain is busy this week, building crucial neural pathways. The baby is about 1.6 centimeters long. Even tiny little taste buds are forming!

9 weeks

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Serious growth is still happening. Your baby is now about 2.3 centimeters long with tiny earlobes, and small eyes behind closed eyelids. She/He has wrists and ankles and elbows, and the genitals have begun to form. The placenta is working overtime now to make nutrients for your baby.

10 weeks

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Now your baby is over 3 cm in length, moving around and swallowing fluid. Her/His organs are fully formed and functional already. Her/His head is almost twice the length of her/his body, and the forehead bulges, but soon she/he will take on more typical baby features. You can even see the outline of her/his spine, peach-fuzz hair and tiny fingernails.

11 weeks

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Your baby is now 4 cm long and is moving around all the time. The movements are slow and easy but will soon become more refined. Tooth buds and toenails and even fingerprints are in place already, and soon the most critical work will be done–then your baby’s job will be to grow fast.

12 weeks

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You can’t feel her/his moving around yet, but she/he can feel you-when you poke your belly, she/he moves in response. She/he is 4.5 centimeters long, is forming the synapses that will be the brain, and is beginning to look much more human. Her/His kidneys have begun to work and her/his liver is making bile.

 

Pregnancy Week by Week--Second Trimester

Timeline

Descriptions

13 weeks

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Your baby is now the size of a pea pod, and those tiny fingerprints are complete. Your baby also has developed the sucking muscles in her/his face, so she/he is often rooting around, preparing for the day when she/he is able to drink from your breast. If you have a girl, she has over two million eggs in her tiny ovaries.

14 weeks

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Your baby’s body is finally growing faster than her/his head, so she/he’s catching up fast! Her/His hair is beginning to grow, even her/his eyebrows. Her/His very fine skin is being covered with a downy hair, but this will likely disappear before birth. She/He can suck her/his thumb and make all sorts of facial expressions now.

15 weeks

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She/He is just over 9 centimeters long now. Your baby gets the hiccups quite a bit, but you probably can’t feel anything like that yet–just wait! When she/he gets a bit bigger, you will. Her/His legs and arms are longer and all the joints are working. The genitals of your baby are developed enough to probably tell if it’s a boy or a girl.

16 weeks

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Imagine an avocado – that’s how big your baby is right now. Her/His umbilical cord has become a favorite toy, and she/he plays with it quite a bit. Her/His eyes are more toward the front of the head now, and she/he holds her/his head up. She/He breathes in amniotic fluid, giving her/his lungs a workout.

17 weeks

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Your baby’s skeleton is made up of mostly cartilage right now, but it will harden in the coming weeks. Myelin is winding its way around the spinal cord, protecting it. She/He even has sweat glands! Your baby is now about 11 centimeters long.

18 weeks

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The ears of your baby are fully formed, and she/he is breathing, her/his chest moving up and down. More blood vessels are visible through the very thin skin. She/He is about 12 centimeters long and very active, moving all over the place.

19 weeks

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All those nerves are developing, and your baby will reach a peak of sensory development this week. He’s about 14 centimeters long. Your baby is moving even more now, and it is likely she/he is big enough for you to actually feel her/him for the first time.

20 weeks

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Your baby is swallowing much more this week, and her/his body is being covered with a waxy, fatty substance that will protect her/him in the womb and during the birth. Her/His bowel is starting to work, producing meconium, which will be her/his first bowel movement after birth. Until now your baby has been measured from head to butt, but if you were to measure your baby from head to heels, she/he is about 26 centimeters long.

21 weeks

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Those tiny eyebrows and eyelids are fully developed, and now your baby can blink. She/He has put on about another centimeter in length and has been putting on serious weight. If it’s a boy, the testes will begin to descend from the scrotum.

22 weeks

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Now your baby actually looks like a newborn, though extremely tiny. She/He has put on another centimeter, the pancreas is starting to work, and her/his tiny gums have small tooth buds. Her/His eyes are formed, but her/his skin is still translucent.

23 weeks

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The big news this week is hearing: Your child can now hear the things around him, such as your heartbeat, your voice and some loud sounds from outside your body, like a vacuum cleaner or a loud car. She/He is about 29 centimeters now.

24 weeks

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She/He is 30 centimeters long! Taste buds, footprints and branches of the lungs are forming rapidly. The brain is growing in leaps and bounds now.

25 weeks

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Now your baby is growing fast with 35 centimeters long. She/He is putting on serious weight and preparing for the journey to the outside world. The optic nerve is working, and your baby will often turn her/his head to look in the direction of a light shining on your belly.

26 weeks

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Your baby’s eyes are now opening, and her/his hearing is more acute– she/he can actually hear the conversations you have with other people now. She/He is taking small breaths of fluid, preparing for the moment when she/he will breathe in air. She/He is about 36 centimeters long and putting on weight every day.

 

Pregnancy Week by Week--Third Trimester

Timeline

Descriptions

27 weeks

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Your baby is getting into a regular sleep-wake cycle, and might even be dreaming. More brain tissue is developing rapidly, and your baby is also having more hiccups. You can definitely feel them now.

28 weeks

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Your baby is 38 centimeters long, and she/he now has long eyelashes that blink when she/he looks around. She/He is putting on layers of fat and getting bigger, and her/his bones are still pliable, but will be much harder after she/he is born.

29 weeks

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Hair is growing like crazy now, and your baby is about 39 centimeters long. If it’s a boy, the testes have descended. If it’s a girl, the clitoris is already there, covered by the labia. The head is getting much bigger, and your baby now reacts to sight and sound.

30 weeks

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The lungs and digestive tract are developed, and your baby continues to open and close her/his eyes. She/He won’t put on much length from this point but she/he will put on weight as she/he prepares for life outside the womb. Your baby can now track a light that you shine on your belly, and maybe even reach out to touch it.

31 weeks

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Your baby is finally proportionate with a body that suits her/his head. She/He isn’t moving around as much, mostly because she/he is confined by the uterus. She/He squirms a lot though, and you will definitely feel that. She/He is about 41 centimeters and is gaining weight rapidly.

32 weeks

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Your baby’s skin is now smooth and her/his body is getting plump with layers of fat. She/He might have a full head of hair, too. She/He is breathing quite a bit now, preparing her/his lungs to work outside of your body.

33 weeks

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Her/His skull is pliable now, and she/he is likely facing downward, preparing for the entry into the world. She/He will put on more weight and her/his skin will become less red and wrinkled, and more like the soft baby skin you expect to see in a newborn.

34 weeks

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She/He is still growing, and now she/he can definitely hear everything you say, so feel free to talk to her/him! She/He is about 45 centimeters long from head to toe.

35 weeks

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She/He is stretching and squirming a lot, and you might even be able to identify a little elbow, foot or knee pushing against your body from the inside. Kidneys and liver are developed now, and the lungs are ready to breathe in that fresh air.

36 weeks

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At this point, your baby is constantly putting on weight and is pressing down hard into your pelvis, preparing for the birth. At this point, your baby is almost full-term!

37 weeks

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Your baby is now settled into your pelvis, leaving more room for her/his legs and feet. Most of the downy hair that covered her/him is gone, and so is the waxy white covering that protected her/him in the womb.

38 weeks

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Your baby’s organs are fully developed, and the lungs are still perfecting themselves. They won’t be entirely mature until a few hours after your baby is born, when she/he finally settles into a normal breathing pattern. Right now you are full term, and you could have your baby any day. She/He’s ready!

39 weeks

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Your baby is now ready to enter the world. All those eyebrows and eyelashes and fingers and toes–even tiny toenails–are fully formed. Your baby is losing skin cells and growing new ones, just as she/he will for every day of her/his life. The skull bones aren’t fused yet, to allow your baby to fit through the birth canal.

40 weeks

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Still pregnant? No worries! Many women go past their due date, but it’s not a cause for concern. Your baby is entirely happy and healthy right where she/he is, and a few extra days won’t hurt her/him. But get ready, because one day very soon, she/he will decide it’s time to make that grand entrance!

For more on how your baby grows inside you, this video can help: