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Get to Know the Fetal Development Week by Week

So, either you are pregnant or if you are planning to start a family of your own and are curious to know about fetal development week by week, right? First of all, congratulations! The growing healthy baby, or development fetus in medical terms, goes through a gestation period of 9 months, or 36 weeks or so as a little cell develops into a healthy baby.

Fetal development chart for the First Trimester of Pregnancy

Week 1 & 2

The first two weeks mark the time when you ovulate and when the fertilization of the egg or ovum takes place. After a sperm penetrates an egg/ovum, the fertilization takes place within 12 to 24 hours. Once the egg is fertilized, it leads to a series of complicated processes which finally leads to the birth of a healthy baby. After fertilization, the egg starts to multiply into several cells and moves from the fallopian tube to the uterus to get embedded and start receiving the nutrition for growth.

Week 3

The fertilized egg is nestled comfortably in the nutrient-dense lining of the uterus now. It is a ball of multiple rapidly multiplying cells which are required to make a healthy baby. This ball is called a blastocyst and starts producing the pregnancy hormone called HCG. The rise in the levels of pregnancy hormone sends a message to the ovaries that the implantation of the fertilized egg has happened in the uterus, and thus it should stop releasing the eggs. It is the levels of HCG that are measured by various pregnancy tests to confirm the same.

Also Read: 5 Super Easy, Quick and Healthy Recipes for Pregnant Women

Week 4

The successfully implanted egg has now grown into an embryo, and you are 4-weeks away from your last period. When you take a home pregnancy test, you will find that you are positive. The size of the embryo is that of a poppy seed.

Week 5

The size of your baby at week 5 is equivalent to that of a sesame seed, and it appears to look more like a tadpole. The blood circulation system has started to develop, and a tiny heart starts beating now.

Week 6

During the sixth week on the fetal development chart, your baby’s size is that of a lentil, but you can see that baby’s mouth, ears and nose have started shaping up, and the intestines and brain development have started.

Week 7

This is when the size of the healthy baby almost doubles the size it was a week before. It is almost like a blueberry now. It might still have a tail at the end, but it will soon begin to disappear. The smaller paddle-like shape appears in place of arms and legs as the fetal development happens.

Week 8

Fetal development week by week brings newer progress reports. During Week 8, your baby is the size of a kidney bean. The primitive neural pathways have started developing, and the breathing tubes extend from the throat to the lungs now. By this week, the baby has started to move inside, but you might not start feeling it yet.

Week 9

After the first two months, during the ninth week of pregnancy, the embryonic tail of the baby has disappeared, and the basic physiology is in place now. It also has tiny earlobes now. The healthy baby is the size of a grape and weighs about an ounce. This is when it will start gaining weight quickly and considerably.

Week 10

During the tenth week, your healthy baby has crossed the crucial part of development. His skin might still be translucent, but the finer details like nails have begun to develop.

Week 11

So, your healthy baby is almost completely formed now. He/she is the size of a fig and has started stretching, kicking, and even hiccupping as the development of the diaphragm happens, but you might not start feeling it yet.

Week 12

The fetal development week by week is happening rapidly now. The baby is the size of a lemon now and will feel it when you gently poke your tummy. This week marks the end of the first trimester of your pregnancy, and this is also when the reflexes of your healthy baby kick in. She can now open and close her hands or curl her toes.

Fetal development chart for the Second Trimester of Pregnancy

Week 13

This week marks the starting of the second trimester. This is when the symptoms like nausea, morning sickness and tiredness disappear, and you might start feeling energetic again. The size of your baby is that of a pea pod. Your baby’s tiny little finger has developed its unique fingerprints, and if it is a girl, her ovaries contain over 2 million eggs now!

Week 14 & 15

This is when the baby has started using his reflexes and facial muscles. During an ultrasound, you might even catch him sucking his thumb. The eyes might still be closed, but he can sense light. If you direct a beam of light towards your tummy, he will move away from the beam. This is also when you can get to know the gender of the baby. His size is that of an apple.

Week 16

The patterns on his scalp are developing, but the hair is yet to grow. The ears are also closer to the final position and shape. He has started using his legs and hands more. So get ready to feel his first kick during this week!

Week 17 & 18

During these weeks, your baby grows from a turnip to the size of a bell pepper. The skeleton, which was earlier present as soft cartilage, has started to harden as bones. You can start feeling his movement inside more prominently now.

Week 19 & 20

During these weeks of fetal development, your baby is big as an heirloom tomato. Her senses – vision, hearing, smell, taste and touch are starting to develop more prominently. During this fetal development week by week is when you can start talking to her, and she will be able to hear your voice. Your baby’s digestive system has also started working, and she has started accumulating meconium, which is the dark, sticky goo which she will pass as her first poop.

Week 21 & 22

Your baby has fully grown into a miniature baby and has been full-on kicking against the walls of your womb. You might have grown familiar with her activity now. She is as big as a carrot now.

Week 23 & 24

In the fetal development chart during these weeks, your baby is big as an ear of corn now. He hearing has developed and she would also be able to recognize a few sounds outside the womb now. Week 24 also marks the end of the second trimester.

Fetal development chart for the Third Trimester of Pregnancy

Week 25 & 26

With the start of the third trimester of your pregnancy, your baby’s skin has started to fill with baby fat. Her features like lips and eyes are more distinct now. She is also inhaling and exhaling the amniotic fluid which is necessary for the development of the lungs. This is a good practice for her first breath in the fresh air outside.

Week 27 & 28

Your baby is fully developed and has started taking room inside your body. She is the size of a large eggplant now. You might start feeling pressure on the bladder and have been peeing a lot now. She also has a waking and sleeping time and her brain is quite active now. Her lungs are fully developed as well. Her eyesight is developing and she can now move her eyelids.

Week 29 & 30

Your healthy baby’s muscles are ready to function outside your womb but her head is still growing to make room for her developing brain. She is the size of a very large cabbage now.

Week 31 & 32

These are some of the most crucial weeks of the fetal development chart as your body enters the last month of pregnancy. Your baby is almost ready for a life outside. Her brain and neural systems are fully developed. This is also the time when you must be gaining from half a kilo to a kilo per day. Half of that weight goes directly to your baby as the skin is getting stuffed with the fat. Her kidneys are now completely developed and the liver can also process the waste now. This is also the time when she has started losing the fine down now, a waxy substance that covered and protected her skin.

Many babies can get born during this period and have no health complications as such.

Week 33 & 34

You are close to your due date now and the wombs are getting quite smaller for your baby to fit into now. You might get into labor any time. Your baby is fully developed and is ready for a life outside. Before leaving your womb and entering this world, your baby might still be putting on fat to be able to regulate his temperature in the world outside.

Also Read: 10 Things Women Ought To Know Before Birthing

Labor & Delivery

It is quite exciting to meet your baby for the first time and it is very normal to feel nervous about the labour and delivery as well. Make sure that you have a birthing plan ready. Be sure to speak with your physician about other alternative delivery procedures to prepare yourself mentally in case of any complications.

Sneha Bisht
Sneha Bisht
Sneha Bisht have completed her master's in public health from Delhi University. She has expertise in writing on Pediatrics, Critical Care, Parenting related topics. Read More..

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