Weekly Pregnancy Stages

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Stages of Pregnancy: Weeks 1-20

Everyone knows that there are three major stages during pregnancy: The first, second and third trimester. What some expecting mothers may not know is exactly how much change occurs each week.

In the first weeks, a woman may not even know she’s pregnant, but in later weeks the baby is growing rapidly. A baby the size of an olive can grow to the size of a lime in the matter of only one week! Each week your baby is developing new parts and appearing more human.

Here is a rundown of the changes you and your baby will experience from the first week to the 20th week of pregnancy.

Pregnancy: Week 1

Many women don’t even realize that they’re pregnant the first week. The major signs of pregnancy aren’t present, but a woman may start to feel tired and have mood swings. However, these signs are often confused with signs that their period is coming. At this point, there is no baby or embryo.

Pregnancy: Week 2

There is still no fetus in week two of pregnancy. You may begin to experience a different set of symptoms, such as tender breasts, dizziness or even nausea.

If a mother knows she is pregnant, she should start considering what lifestyle and dietary changes are appropriate to prepare for the baby’s development. At this stage, women should stop smoking and should start taking the right vitamins and minerals, such as folic acid.

However, many women assume their period is late for other reasons and still do not know that they’re pregnant.

Pregnancy: Week 3

If you don’t know you’re pregnant yet, week three is likely the week you will be running to the store to buy a pregnancy test. You could experience PMS-like symptoms, or more intense symptoms, such as vomiting.

In week three, the baby is a morula, which is an early stage embryo made up of cells that are constantly multiplying. Your baby’s gender, hair, eye and skin colour have already been determined. The size of the baby can vary from .2 mm to .5 mm.

Pregnancy: Week 4

Congrats, you’ve now been pregnant for a whole month!

Sore breasts and vomiting are common during this stage.

Your baby’s brain, spinal cord, heart, head, bones, muscles and tissues are developing. Fetuses are at an increased risk of developing abnormalities at this time, so it’s important that you have stopped smoking and drinking and have implemented a healthy lifestyle.

Your baby is about the size of a poppy seed right now. The heart is beating and the organs are developing.

Pregnancy: Week 5

At 5 weeks, you’re not looking pregnant, but you’ll probably feel bloated. You may also experience the emotional changes that come with higher hormone levels.

Your baby is growing fast and is now about 5 mm long and looks like a tadpole. Your baby’s heart is rapidly developing and the heartbeat may be detectable by an ultrasound. At this stage, your baby receives nourishment through the developing placenta and umbilical cord.

Pregnancy: Week 6

You are now half way through your first trimester.

Many mothers will get their first ultrasounds during the sixth week to ensure that everything is okay with their baby. They will also get their first look at the developing embryo. In these ultrasounds, you will be able to see the baby’s developments occurring at this stage. Developments include ears, nose and mouth.

The baby’s arms and legs don’t appear as full limbs yet; they begin as little stubs. Your baby is about 6 mm long.

Pregnancy: Week 7

Around week seven you may start getting pregnancy cravings for foods you don’t usually like.

A few weeks earlier, your baby was only the size of a poppy seed. Now, your baby is the size of a blueberry. Your baby’s mouth and tongue are forming and the muscles and organs continue to grow. In week seven, your baby is developing his or her blood type.

Pregnancy: Week 8

In week eight, your baby is about 2 cm long and is growing quickly — about 1 mm every day!

This week, your baby’s lungs are developing. Your baby already has little hands and toes, but now they are starting to grow longer and separate, losing their webbing. Your baby will also lose the embryonic tail (which previously made the baby look like a tadpole).

Pregnancy: Week 9

Your baby is now out of the embryonic period and has begun the fetal stage.

The baby weighs only three grams and is about 2.5 cm long, comparable to an olive. Your baby’s organs and muscles are functioning now.

Pregnancy: Week 10

The most important weeks of development are over; however, that doesn’t mean your baby still can’t develop abnormalities.

At this stage, you may have gained up to three pounds, but you aren’t likely showing yet. The weight is understandable when you consider this: Last week your baby was the size of an olive, now your baby is the size of a lime!

The baby’s jawbones are starting to form and the webbing between their fingers and toes is completely gone. If you are having a boy, he will start producing testosterone at this point.

Pregnancy: Week 11

This week, your baby is around 6 cm. Your baby is moving around at this point, but is too small for you to feel the activity. You won’t know your baby’s gender yet, but he or she is starting to develop testes or ovaries. The baby’s ears will have moved from the neck closer to their final position on the side of the head.

Pregnancy: Week 12

At week 12, you’re coming to the end of your first trimester. Good news: The chances of miscarriage significantly decrease past this point. For this reason, many women feel more secure in their pregnancy and decide to announce the pregnancy at this time.

In terms of development, your baby’s vocal cords are forming and their nails are visible. Your baby will start to practice breathing and sucking motions.

This week is great for another reason: You can start using a fetal doppler to hear your baby’s heartbeat!

Pregnancy: Week 13

By week 13, you probably can’t keep the exciting news to yourself.

Your baby is about 7.5 cm long and about 25 g. The fetus now looks like a baby and has learned how to kick, turn their head and yawn. At this stage, their stomach and bowel starts developing and their kidneys are working.

Pregnancy: Week 14

You’ve made it to the second semester and the worst is over in terms of pregnancy symptoms and nausea. At this point, you’re probably starting to show and people are probably starting to comment on your growing baby belly.

Since the baby is getting nutrients from the placenta, your appetite will increase. Your breasts will also continue to ache as they get ready for lactation. Your baby is about 8 cm long and about 42 grams.

Pregnancy: Week 15

Your baby is now around 11.5 cm long and is around the size or an orange. By this time, your baby can hear your voice, so be sure to sing, chat or play some nice music for him or her.

Your baby is moving around and you will sometimes be able to feel kicks. Your baby can now make faces and the taste buds are forming.

Pregnancy: Week 16

Your baby is beginning to build fat underneath his or her skin. Since the genitals are fully developed, this week’s ultrasound will show if your baby is a boy or a girl.

In the 16th week, your milk glands start production, so your breasts will increase in size. Although your baby’s eyes are still closed shut, he or she can detect light. For this reason, your baby may cover their eyes with their hands to protect themselves.

Pregnancy: Week 17

At this point, your baby weighs about 150 g and is about 14 cm long. By now, the bones are finished developing and your baby’s body has come into proportion. Since your baby’s arms and legs are continuing to grow, his or her head doesn’t look so large anymore.

Pregnancy: Week 18

Your baby is about 200 g. He or she is now moving around in full force and you may even feel it! However, don’t panic if you haven’t felt your baby kick yet! Some women have to wait a bit longer for their baby to get larger. If you’re having a girl, she will begin to develop her uterus and fallopian tubes during the 18th week.

Pregnancy: Week 19

During the 19th week of pregnancy, you may begin to experience skin troubles, such as dry or flaky skin. You are more at risk of becoming dehydrated, so be sure to avoid caffeine and drink a lot of water.

By now, your baby is about 240 grams. The baby’s skin is now covered with fine hairs and Vernix, which helps protect the skin. The pigment in your baby’s skin is now starting to develop as well.

Pregnancy: Week 20

You are now in the middle of your second trimester and in the middle of your pregnancy. As your belly continues to grow, you are probably experiencing indigestion and heartburn.

Your baby has now grown to 16.5 cm long and is about the size of a banana. By now, you are probably frequently feeling your baby’s movements. Your baby’s ears are now fully working, and they can be startled by loud noises, so quiet environments may be best.


You have 20 more weeks until your bundle of joy comes into this world! Check back next week to see how your baby develops in the remainder of your pregnancy.

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About Mithu Kuna

Mithu is a tech-savvy entrepreneur. He is a founder of Baby Doppler and enjoys incorporating AI driven technology in baby and maternity IoT devices.

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