Size of fetus month by month

Weeks 1 to 3

Your due date is 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. Here, Jonathan D. Herman, M.D., shares the average baby size by week.

Read more about pregnancy week 1, pregnancy week 2, and pregnancy week 3.

Baby Size at 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 pregnancy week 4.

Baby Size at 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 pregnancy week 5.

Baby Size at Week 6

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

Baby's Length: 0.13 in.

Baby's Weight: Less than 0.04 oz.

Learn more about pregnancy week 6.

Baby Size at Week 7

Your baby is now about the size of a small blueberry. Their 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 pregnancy week 7.

Baby Size at Week 8

Your baby is about the size of a raspberry. Their hands and feet have webbed fingers and toes. Soon this extra tissue between their 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 pregnancy week 8.

Baby Size at 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 pregnancy week 9.

Baby Size at Week 10

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

Baby's Length: 1.22 in.

Baby's Weight: 0.14 ounce

Learn more about pregnancy week 10.

Baby Size at Week 11

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

Baby's Length: 1.61 in.

Baby's Weight: 0.25 oz.

Learn more about pregnancy week 11.

Baby Size at Week 12

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

Baby's Length: 2.13 in.

Baby's Weight: 0.49 oz.

Learn more about pregnancy week 12.

Baby Size at Week 13

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

Baby's Length: 2.91 in.

Baby's Weight: 0.81 oz.

Learn more about pregnancy week 13.

Baby Size at Week 14

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

Baby's Length: 3.42 in.

Baby's Weight: 1.52 oz.

Learn more about pregnancy week 14.

Baby Size at Week 15

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

Baby's Length: 3.98 in.

Baby's Weight: 2.47 oz.

Learn more about pregnancy week 15.

Baby Size at Week 16

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

Baby's Length: 4.57 in.

Baby's Weight: 3.53 oz.

Learn more about pregnancy week 16.

Baby Size at Week 17

Your baby is now the size of a pear. They have 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 pregnancy week 17.

Baby Size at Week 18

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

Baby's Length: 5.59 in.

Baby's Weight: 6.70 oz.

Learn more about pregnancy week 18.

Baby Size at Week 19

Your baby is about the size of a mango. Their legs are now longer than their arms, and they'll start giving you "hello" jabs at regular intervals, which you might 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 pregnancy week 19.

Baby Size at Week 20

Your baby is now the size of a banana. They may have thin eyebrows and sprout some hair on their head.

Baby's Length: 6.46 in.

Baby's Weight: 10.58 oz.

Learn more about pregnancy week 20.

Baby Size at Week 21

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

Baby's Length: 10.51 in.

Baby's Weight: 12.70 oz.

Learn more about pregnancy week 21.

Baby Size at Week 22

Your baby is the size of a papaya. Their lungs are developing rapidly, and they will begin making a protein called surfactant, which will help them breathe independently once they're born.

Baby's Length: 10.94 in.

Baby's Weight: 15.17 oz.

Learn more about pregnancy week 22.

Baby Size at Week 23

Your baby is as big as an eggplant. Their brain and hearing are more developed this week, and they're beginning to recognize your voice.

Baby's Length: 11.38 in.

Baby's Weight: 1.10 lb.

Learn more about pregnancy week 23.

Baby Size at Week 24

Your baby is as long as an ear of corn. Their nostrils are opening now for "practice breathing"; they'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 pregnancy week 24.

Baby Size at Week 25

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

Baby's Length: 13.62 in.

Baby's Weight: 1.46 lb.

Learn more about pregnancy week 25.

Baby Size at Week 26

Your baby is nearly as long as a zucchini. Their eyebrows and eyelashes are well-defined; plus, they have more hair on their head this week.

Baby's Length: 14.02 in.

Baby's Weight: 1.68 lb.

Learn more about pregnancy week 26.

Baby Size at Week 27

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

Baby's Length: 14.41 in.

Baby's Weight: 1.93 lb.

Learn more about pregnancy week 27.

Baby Size at Week 28

Your baby is the size of a kabocha squash, and they're beginning to open their eyes and blink.

Baby's Length: 14.80 in.

Baby's Weight: 2.22 lbs

Learn more about pregnancy week 28.

Baby Size at Week 29

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

Baby's Length: 15.2 in.

Baby's Weight: 2.54 lbs.

Learn more about pregnancy week 29.

Baby Size at Week 30

Your baby is the size of a large cabbage. They have cycles of sleeping and waking. After 30 to 90 minutes of snoozing, they may give you a kick to let you know they're awake.

Baby's Length: 15.71 in.

Baby's Weight: 2.91 lbs.

Learn more about pregnancy week 30.

Baby Size at Week 31

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

Baby's Length: 16.18 in.

Baby's Weight: 3.31 lbs.

Learn more about pregnancy week 31.

Baby Size at Week 32

Your baby is the size of a Napa cabbage. Because their taste buds are developed, they may acquire a preference for the foods you eat, which they sample when they swallow amniotic fluid.

Baby's Length: 16.69 in.

Baby's Weight: 3.75 lbs.

Learn more about pregnancy week 32.

Baby Size at Week 33

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

Baby's Length: 17.20 in.

Baby's Weight: 4.23 lbs.

Learn more about pregnancy week 33.

Baby Size at Week 34

Your baby is the size of a cantaloupe. Their bones are fully developed by now, and they're turning their head, pirouetting, and moving their body from side to side.

Baby's Length: 17.72 in.

Baby's Weight: 4.73 lbs.

Learn more about pregnancy week 34.

Baby Size at Week 35

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

Baby's Length: 18.19 in.

Baby's Weight: 5.25 lbs.

Learn more about pregnancy week 35.

Baby Size at Week 36

Your baby is now the size of a head of romaine lettuce, and their wrinkly suit of skin is filling out as they get plumper.

Baby's Length: 18.66 in.

Baby's Weight: 5.78 lbs.

Learn more about pregnancy week 36.

Baby Size at Week 37

Your baby is as long as stalk of Swiss chard. Because they're running out of room in your uterus, they mostly stretch and wiggle, instead of delivering big kicks.

Baby's Length: 19.13 in.

Baby's Weight: 6.30 lbs.

Learn more about pregnancy week 37.

Baby Size at Week 38

Your baby is the length of a stalk of rhubarb. Connections are forming in their brain that will help them swallow and even sleep better once they're born.

Baby's Length: 19.61 in.

Baby's Weight: 6.80 lbs.

Learn more about pregnancy week 38.

Baby Size at Weeks 39

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

Baby's Length: 19.96 in.

Baby's Weight: 7.25 lbs.

Learn more about pregnancy week 39.

Baby Size at Weeks 40-42

By the time they're 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 they'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 pregnancy week 40, pregnancy week 41, and pregnancy week 42.

What size is a month fetus?

What size is a 4 month Foetus?

Which month baby grows faster in womb?

How big is a 5 month old fetus?