How Big is Your Baby? Fetal Development Week by Week


When you conceive, initially your belly does not show up and hence it is quite incomprehensible to others that you are carrying. However, as the months or the weeks progress, the embryo grows into a foetus, which further grows into a fine baby that you deliver approximately at the end of your ten-month tenure! This development and transformation of the egg is indeed a fascinating affair! Since it is all happening inside your body, you would all the more want to know how your big your baby is, with the passage of every day! To ease your curiosity, here is a week by week description of fetal development of the potential size of your baby at that point in time:

Pregnancy Week-by-Week Comparison of Fetal Development

Fetal Development Week by Week

Week 1

Well, in the first week of pregnancy, you are not exactly ‘pregnant’ in the real sense of it. This is because your body is getting ready for the conception after fertilisation of the egg. Hence, even if the egg has fertilised, you are yet to be confirmed as pregnant. This is why you won’t see your baby yet.Week 2 of Pregnancy

Week 2

The same is the case in the second week of your pregnancy. If you, however, feel that you might be pregnant, visit the doctor in order to get the confirmation on this.

Week 3

At 3 weeks pregnant, you have most probably conceived, with the conception having occurred only a few days ago. From now on, or maybe from the next week onwards, you will gradually start experiencing the symptoms.

Week 4

This is the week from which you can actually say that you are officially pregnant, and can start measuring or keeping a track of the size of the foetus. Congratulations! At 4 weeks, the foetus is barely the size of a poppy seed, weighing almost nothing!


Week 5

At week 5, the foetus is just about the size of an apple seed, measuring approximately 0.13 inches from the crown to the rump. In the next couple of weeks, the foetus will literally grow twice as much as its current size. Surely, you are excited for more!

Week 6

By the time you are about 1.5 months pregnant, your foetus will be the size of a sweet pea. At week 6 the average size of the baby now is 0.25 inches from the crown to the rump.

Week 7

By now the foetus has grown a bit more in size and is now more like a blueberry. At week 7 the size has doubled in comparison to what is was even last week. It is growing quickly! The foetus now measures approximately 0.51 inches.

Week 8

From now onwards, that your baby is 8 weeks old, inside the womb, you will rapidly start putting on weight. By this time the foetus is as big as a raspberry, weighing about .04 ounces and measuring about 0.63 inches.

Week 9

The foetus is growing about a millimetre every day. By this week, it is the size of ripe cherry. The size of the foetus is about 0.9 inches and it weight nearly .07 ounces! Around this time, or maybe a week earlier or later, you will have your first prenatal appointment. You will be able to hear your baby’s heartbeat through the ultrasound device! Keep some tissues handy!

Week 10

By the tenth week, the baby is as big as a strawberry! Now the foetus is nearly 1.2 inches long and about 0.14 ounces heavy. The foetus’ length will increase by two times over the next three to four weeks! By the end of this week, your baby’s central organs will be completely developed and will start functioning.


Week 11

The baby by this week has grown into the size of a lime. The length of the foetus is approximately 1.6 inches and it weighs nearly 0.25 ounces. At this point, the baby has a 1:1 head to body ratio, but this will change in the coming few weeks as the body will grow into proper size, which will be proportionate to its head.

Week 12

At week 12, the size of your foetus is that of a plum, weighing nearly 0.50 ounces and measuring about 2.1 inches. By now, all the important organs of the foetus are well developed and are functioning full-fledged. Now you can officially claim to possess a baby bump, which is quite visible!

Week 13

The baby’s brain cells and nerves are developing very quickly, and its limbs are almost already in their proper place. The foetus is now the size of a lemon, measuring about 2.9 inches and weighing nearly 0.81 ounces.

Week 14

By now the baby looks more like a peach! You are officially three months pregnant now! This is a milestone as it marks a trimester in pregnancy. During this week the foetus weighs 1.5 ounces and measures approximately 3.4 inches. At this point, the baby might even be sucking its thumb inside the womb!

Week 15

One week down the line, the baby has grown even more rapidly and is now almost the size of an orange! The foetus weight roughly 2.5 ounces and measures about 4 inches already! Gradually the body is growing and the 1:1 proportion is fading out, giving the body a more natural look.


Week 16

There is an avocado inside your belly! This ‘fruit’ measures approximately 4.6 inches and is about 3.5 ounces heavy. The baby’s ear bones are growing gradually, and its sense of hearing is also developing!

Week 17

Your baby is indeed growing quicker than you imagine! Only at week 17, the foetus is as big as a pomegranate, weighing about 5.9 ounces and measuring nearly 5.1 inches. During this phase, you are gaining about 1.5 pounds per week, on an average. The baby is developing some fat and flesh around the bones.

Week 18

This week, you are officially four months pregnant and the baby is nearly the size of an artichoke. The foetus now weighs 6.7 ounces and is about 5.6 inches long from crown to toe. By now the little one is wiggling inside your womb! The baby is also probably sucking its tiny thumb!

Week 19

The baby at week 19 is approximately the size of a ripe mango. The length of the foetus is nearly 6 inches and it weighs about 8.5 ounces. The baby is gradually developing a thin protective layer around its skin, called vernix caseosa.

Week 20

Now the foetus is the size of a banana that is 10.2 ounces and approximately 6.5 inches in length from crown to rump. By now you have probably already gained 10 pounds, at an average rate of gaining a couple of pounds each week.

Week 21

The foetus has now grown by quite a few inches and pounds, and is roughly the size of an endive. At week 21 the baby weighs nearly 12.7 ounces and measures approximately 10.5 inches. Since the baby is bigger now, you are likely to feel some of its movements inside the womb. The baby is now developing a proper digestive system to take in all the nutritious foods that you feed yourself!


Week 22

The baby is now a cute little round ball of fluff like a coconut! The baby is gradually beginning to crowd your abdominal and intestinal areas, putting pressure on your bladder and making you want to pee at shorter intervals. The foetus is nearly 11 inches long by now and weighs approximately 15.2 ounces. The baby’s facial features are more prominent now as the lips and eyes are well developed.

Week 23

This week, the baby is a ripe grapefruit! The baby now is 11.4 inches from head to toe, and weighs nearly 1.1 pounds. Finally the time has come to start weighing your baby in pounds! By now the baby’s face has fully developed and the little one is even growing nipples!

Week 24

By week 24, the foetus is more like a cantaloupe, weighing 1.3 pounds and measuring approximately 11.8 inches. Yes, the baby is almost a foot long! The baby’s skin is gradually becoming more opaque and is developing a pinkish tinge.

Week 25

The baby is now developing a sense of up and down, and is growing some hairs on its tiny head! During this week, you can see that the baby is the size of a cauliflower, weighing 1.5 pounds and measuring nearly 13.6 inches from head to toe.

Week 26

At week 25, the baby has grown significantly bigger and has developed into the size of kale. The foetus now weighs about 1.7 pounds and measures 14 inches. The baby id definitely kicking, waiting to come out already!

Week 27

The foetus is as big a lettuce now, weighing 1.9 pounds and about 14.4 inches long, from head to toe. You are nearly six months pregnant now! You have crossed more than half the journey. Congratulations on making it this far!


Week 28

The baby has grown further into the shape of an eggplant. The baby is now about 14.8 inches long and 2.2 pounds heavy. The foetus is rapidly developing layers of fat around its outer skin and in the subcutaneous areas.

Week 29

Welcome to the official third trimester of pregnancy! The baby’s wrinkled skin is gradually getting smoother as it is growing in volume. The foetus is now as big as an acorn squash, weighing 2.5 pounds and its length being approximately 15.2 inches. No wonder those kicks are getting stronger with each passing day!

Week 30

By week 30, the baby turns into a zucchini-sized ball of cuteness! The foetus is 15.7 inches long and weighs nearly 3 pounds. That’s the major reason behind your weight gain! At this stage, the baby’s brain is almost developed, and is in its last stage of reaching refinement and perfection!

Week 31

The baby, at this week, is like an asparagus. The foetus is getting heavier each day as it now weighs approximately 3.3 pounds and is 16.2 inches long. The baby’s senses of smell and hearing are now fully developed!

Week 32

Welcome to the eighth month of pregnancy! The baby is now as big and oval shaped as a ripe gully grown squash, weighing 3.8 pounds and measuring about 16.7 inches from its head to toe. The baby is now getting ready for its descending act, which is called falling. Hence, it is now turning over into a head-down position.

Week 33

At 33 weeks, the foetus is as big as celery, weighing 4.2 pounds and measuring up to 17.2 inches in terms of length. By now you have gained about 25 pounds, on an average. The baby is now breathing, sucking, swallowing, blinking – basically doing everything that will be required to sustain life outside the womb as well! The baby is getting trained!


Week 34

The baby has now grown to be almost the size of a butternut squash, which is 17.7 inches long and weighs about 4.7 pounds. You are just about six weeks away from delivering the baby!

Week 35

Your baby is now the size of a pineapple, crowding your abdominal area even more. But, the wait is not for too long now! The foetus is approximately 18.2 inches from its head to heel, and it weighs around 5.3 pounds.

Week 36

The baby is more like a papaya now! It is 18.7 inches long and 5.8pounds heavy. Welcome to week 9! You are almost there! The baby’s circulatory system and cardiovascular system, both are already functioning properly.

Week 37

By week 37, the foetus is more like romaine lettuce, weighing 6.3 pounds and measuring about 19.1 inches form head to heel. The baby is just fine and is waiting to pop out!

Week 38

By now the baby is as big as a winter melon! It is of 19.6 inches in length and it weighs nearly 7 pounds. The baby probably already has an inch’s length of hair on its head!

Week 39

The baby has reached its full term by now, and is as big as a pumpkin. The baby is 20 inches long and weighs nearly 7.3 pounds. Buy now you must be ready for labour, as it might just occur any time.


Week 40

This is most probably the last and ultimate week, during which your baby will have attained the size of a watermelon. The almost ready foetus weighs 7.6 pounds or even 8 pounds at times, and is 20.2 inches long. The baby’s body is now functioning like a normal human.

Each time you visit the gynaecologist for an ultrasound test, you will get to know about the size of your baby, and its bodily developments. You have to be ready accordingly, to make sure that you are well prepared for the labour period, and delivery. Ask your doctor everything you have in mind, and enjoy the wonderful journey towards motherhood!

Hope this article was of help to you! Please share your comments/queries/tips with us and help us create a world full of Happy, Healthy and Empowered Women and Healthy Babies!!