How Big is Your Baby This Week?

Weeks 1 to 3

Your due date will be calculated from the first day of your last menstrual period. Conception occurs about two weeks from this day, and that's when you're truly considered pregnant. In just 40 short weeks, your baby will grow from the size of a tiny seed to the size of a plump watermelon.

• Watch as the ovulation process and fertilization takes place

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Week 4

Your fertilized egg, known as a zygote, is a ball of 32 cells that's about the size of a poppy seed. It's at this stage that the cells separate into three distinct layers from which your baby's internal organs and skin will develop.

Baby's Length: about 0.014 to 0.04 in.

Baby's Weight: less than 0.04 oz.

• Learn more about Week 4 of pregnancy

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Week 5

The ball of cells now resembles a tadpole and is as big as a peppercorn. The creation of the brain, spinal cord, heart, and blood vessels is already well under way.

Baby's Length: about 0.05 in.

Baby's Weight: less than 0.04 oz.

• Learn more about Week 5 of pregnancy

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Week 6

Your little one has tripled in size and is protected by amniotic fluid. Although he's grown by leaps and bounds, he's still only about the size of a pomegranate seed.

Baby's Length: about 1/8 in.

Baby's Weight: less than 0.04 oz.

• Learn more about Week 6 of pregnancy

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Week 7

Your baby is now about the size of a small blueberry. Her arm buds, which formed last week, now look like paddles.

Baby's Length: about .5 in.

Baby's Weight: less than 0.04 oz.

• Learn more about Week 7 of pregnancy

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Week 8

Your baby is about the size of a cranberry bean. His hands and feet have webbed fingers and toes. Soon this extra tissue between his digits will be reabsorbed to reveal individual fingers and toes.

Baby's Length: about 0.63 in.

Baby's Weight: less than 0.04 oz.

Note: From week 8 through week 20, measurements are taken from crown to rump.

• Learn more about Week 8 of pregnancy

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Week 9

Your baby has graduated from embryo to fetus—and is now about the size of a cherry. The digestive tract and reproductive organs are formed, but it's still too early for even a skilled technician to tell whether you're having a boy or a girl.

Baby's Length: about .9 in.

Baby's Weight: about .07 oz.

• Learn more about Week 9 of pregnancy

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Week 10

Your baby is about the size of a kumquat and can stretch his spine. Her eyes and eyelids are more developed and her eyebrows are beginning to grow.

Baby's Length: 1.22 in.

Baby's Weight: 0.14 ounce

• Learn more about Week 10 of pregnancy

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Week 11

Your baby is about the size of a Brussels sprout. From now through week 20 of your pregnancy, he'll increase 30-fold in weight and triple in length.

Baby's Length: 1.61 in.

Baby's Weight: 0.25 oz.

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Week 12

Your baby is almost three inches long now, about the size of a passion fruit. Fingernails, toenails, and bones are forming, and a fine layer of hair covers most of her body.

Baby's Length: 2.13 in.

Baby's Weight: 0.49 oz.

• Learn more about Week 12 of pregnancy

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Week 13

Your beautiful baby is the size of a Meyer lemon this week—and his vocal cords are beginning to develop.

Baby's Length: 2.91 in.

Baby's Weight: 0.81 oz.

• Learn more about Week 13 of pregnancy

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Week 14

As you enter your second trimester, your baby is the size of a nectarine. All of her internal organs formed during the first trimester, and they will continue to mature from now until she's born.

Baby's Length: 3.42 in.

Baby's Weight: 1.52 oz.

• Learn more about Week 14 of pregnancy

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Week 15

Your baby is now the size of an apple. His brain now controls all the muscles in her body; he is able to move. Yes, he'll even do somersaults! But if this is your first baby, you probably won't feel him moving for several more weeks.

Baby's Length: 3.98 in.

Baby's Weight: 2.47 oz.

• Learn more about Week 15 of pregnancy

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Week 16

Your baby is now the size of an avocado—and she can make a fist and even suck her thumb.

Baby's Length: 4.57 in.

Baby's Weight: 3.53 oz.

• Learn more about Week 16 of pregnancy

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Week 17

Your baby is now the size of a pear. He has hiccupped before, but this is the first time you might feel it.

Baby's Length: 5.12 in.

Baby's Weight: 4.94 oz.

• Learn more about Week 17 of pregnancy

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Week 18

Your baby is now about the size of a sweet potato—and her tiny fingers now have unique fingerprints!

Baby's Length: 5.59 in.

Baby's Weight: 6.70 oz.

• Learn more about Week 18 of pregnancy

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Week 19

Your baby is now about the size of a mango. His legs are now longer than his arms, and he'll start giving you "hello" jabs at regular intervals, which you may be able to feel if this is your second or third pregnancy. First-time moms still might not feel anything for a few more weeks.

Baby's Length: 6.02 in.

Baby's Weight: 8.47 oz.

• Learn more about Week 19 of pregnancy

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Week 20

Your baby is now the size of a small artichoke. She may have thin eyebrows and is sprouting some hair on her head.

Baby's Length: 6.46 in.

Baby's Weight: 10.58 oz.

• Learn more about Week 20 of pregnancy

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Week 21

Your baby is as long as a carrot, and his skin now responds to touch. If you put pressure on your belly, he'll move away or push back.

Baby's Length: 10.51 in.

Baby's Weight: 12.70 oz.

• Learn more about Week 21 of pregnancy

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Week 23

Your baby is as big as an eggplant. His brain and hearing are more developed this week, and he's beginning to recognize your voice.

Baby's Length: 11.38 in.

Baby's Weight: 1.10 lb.

• Learn more about Week 23 of pregnancy

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Week 24

Your baby is as long as an ear of corn. Her nostrils are opening now for "practice breathing"; she'll go through the same motions of real breathing but inhale amniotic fluid instead of air.

Baby's Length: 11.81 in.

Baby's Weight: 1.32 lb.

• Learn more about Week 24 of pregnancy

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Week 25

Your baby is the size of an acorn squash. He's developing a firm grasp and may reach out and grab the umbilical cord. He can also stick out his tongue!

• Learn more about Week 25 of pregnancy

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Week 26

Your baby is nearly as long as a zucchini. Her eyebrows and eyelashes are well-defined; plus, she has more hair on her head this week.

Baby's Length: 14.02 in.

Baby's Weight: 1.68 lb.

• Learn more about Week 26 of pregnancy

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Week 27

Your baby is now the size of a cauliflower. At this point, he may be able to distinguish between your voice and your husband's or partner's voice.

Baby's Length: 14.41 in.

Baby's Weight: 1.93 lb.

• Learn more about Week 27 of pregnancy

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Week 28

Your baby is the size of a kabocha squash, and she is beginning to open her eyes and blink.

Baby's Length: 14.80 in.

Baby's Weight: 2.22 lbs

• Learn more about Week 28 of pregnancy

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Week 29

Your baby is the size of a large butternut squash. His skin is still wrinkly, but as fat accumulates, he will fill out.

Baby's Length: 15.2 in.

Baby's Weight: 2.54 lbs.

• Learn more about Week 29 of pregnancy

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Week 30

Your baby is the size of a large cabbage. She has cycles of sleeping and waking. After 30 to 90 minutes of snoozing, she may give you a kick to let you know she's awake.

Baby's Length: 15.71 in.

Baby's Weight: 2.91 lbs.

• Learn more about Week 30 of pregnancy

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Week 31

Your baby is about as long as a bunch of leeks, and she will now gain as much as a half pound per week until she's born.

Baby's Length: 16.18 in.

Baby's Weight: 3.31 lbs.

• Learn more about Week 31 of pregnancy

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Week 32

Your baby is the size of a Napa cabbage. Because her taste buds are developed, she may acquire a preference for the foods you eat, which she samples when she swallows amniotic fluid.

Baby's Length: 16.69 in.

Baby's Weight: 3.75 lbs.

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Week 33

Your baby is the size of a pineapple. Lanugo, the fine hair that covered her entire body and helped keep her warm as she developed, is starting to disappear, but there might still be patches of it on her shoulders and back.

Baby's Length: 17.20 in.

Baby's Weight: 4.23 lbs.

• Learn more about Week 33 of pregnancy

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Week 34

Your baby is the size of a cantaloupe. Her bones are fully developed by now, and she's turning her head, pirouetting, and moving her body from side to side.

Baby's Length: 17.72 in.

Baby's Weight: 4.73 lbs.

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Week 35

Your baby is the size of a honeydew melon. In preparation for birth, he is now upside down in your uterus.

Baby's Length: 18.19 in.

Baby's Weight: 5.25 lbs.

• Learn more about Week 35 of pregnancy

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Week 36

Your baby is now the size of a canary melon, and her wrinkly suit of skin is filling out as she gets plumper.

Baby's Length: 18.66 in.

Baby's Weight: 5.78 lbs.

• Learn more about Week 36 of pregnancy

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Week 37

Your baby is as long as stalk of Swiss chard. Because he's running out of room in your uterus, he mostly stretches and wiggles, instead of delivering big kicks.

Baby's Length: 19.13 in.

Baby's Weight: 6.30 lbs.

• Learn more about Week 37 of pregnancy

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Week 38

Your baby is the length of a stalk of rhubarb. Connections are forming in her brain that will help her swallow and even sleep better once she's born.

Baby's Length: 19.61 in.

Baby's Weight: 6.80 lbs.

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Weeks 39

Your baby now weighs as much as a mini watermelon. At this point, he has shed most of that white creamy substance called vernix and the fine, fur-like hair called lanugo that has covered his skin since the middle of your second trimester.

Baby's Length: 19.96 in.

Baby's Weight: 7.25 lbs.

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Weeks 40-42

By the time she's born, your baby may be watermelon-size. You're expecting to give birth this week, but don't worry if your baby decides to stick around a little longer. Many first babies are late, and she'll be worth the wait—we promise!

Baby's Length: 20.16 to 21 in.

Baby's Weight: 7.63 to 9 lbs.

• Learn more about Week 40 of pregnancy

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