Week by Week Pregnancy: Learn How Your Baby Develops Each Week

Any mother who tracks her week by week pregnancy can sleep soundly knowing her baby is growing to become a healthy human being. Most moms take the fetal development week by week for granted, but it is very important for any pregnancy concerns you might have. If you are wondering, “How can I calculate my weeks of pregnancy?” this will certainly help. It’s also partly how doctors estimate when your baby is due. Find out how your baby develops every week!

Week by Week Pregnancy: What You Should Know

1. Week One

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In the first week, there is practically nothing to think about yet. During your first week, changes happen more to your body than to your baby. Hormones change, certain bodily responses change. Your body is preparing for his or her arrival!

2. Week Two

The pace picks up during the second week of pregnancy. The fertilized egg travels from the Fallopian tube down to the uterus. In the uterus, cells divide and a zygote forms.

3. Week Three

If you’re wondering when you’ll start noticing that you’re pregnant, it’s usually during the third week. The blastocyst, or fertilized egg, starts its long development process; it will eventually become the placenta and embryo. The level of maternal hormones also rises and now you really feel your pregnancy.

4. Week Four

Because you feel things more strongly now, the fourth week is usually when you start keeping track of your week by week pregnancy. At this point, your baby is about the size of a poppy seed. He or she is still too little to resemble anything in a sonogram, but you can feel something is growing inside you. Also, the cells at this point start to form layers that will become the different parts of your baby.

5. Week Five

From the size of a poppy seed, your baby is now the size of a sesame seed! Keeping a record of your week by week pregnancy will sometimes make you feel like there’s not much of a difference, but every baby step counts. During the fifth week, the baby is called an embryo and the three layers that began to develop earlier are more distinct. You now have the ectoderm, mesoderm, and endoderm.

6. Week Six

During the sixth week, your baby is the size of a lentil! Organs are starting to take shape as well. The baby’s shape is slightly distinct too, but he or she still doesn’t look like our idea of a baby.

7. Week Seven

If you’re excited to see your baby’s face, week seven is the week to wait for. At this stage, the baby, though still called an embryo, is starting to develop his or her face and brain. Nostrils and eyelids are also more noticeable. Your baby starts to have little hands as well.

8. Week Eight

From resembling a little tailed creature in the previous weeks, your baby, during the eighth week, starts to look like an actual baby! All your baby’s body parts now take on a different shape. The hands and feet are more pronounced, the eyelids start finding their place, and, more importantly, the embryonic tail is gone. The baby’s nervous and muscular systems are also beginning to function.

9. Week Nine

Perhaps the most important thing in week nine is the maturing of the baby’s heart. Your baby’s heartbeat has always been there, but during the ninth week, it starts growing into its four chambers. Plus, the placenta is now fully formed. Everything is set for your baby’s growth!

10. Week Ten

Although your baby is still only about an inch long, he or she is ready to become a new human being and is now entering the fetal stage. During the tenth week of pregnancy, the baby’s vital organs are starting to perform their functions. This includes the beginning of his or her spinal column’s growth, which is essential to any human being’s consciousness.

11. Week Eleven

This is the week when your baby starts learning how to breathe. Although the baby is technically not breathing air, he or she has amniotic fluid to provide life. The tongue, palate, and nasal passages also start finding their place during the eleventh week so the baby can inhale and exhale in his or her own way.

12. Week Twelve

Week twelve of pregnancy is a sort of blessing. At this point, your pregnancy hormones are stabilizing. Along with this, your baby’s head is starting to resemble an actual human head! The most noticeable thing about this stage is the movement of your baby’s eyes and ears. They are now in their right places.

13. Week Thirteen

You could call the thirteenth week of pregnancy the week of identity formation because this is when your baby’s fingertips develop fingerprints! Even before your baby sees the world, the womb prepares him or her for a lifelong process of letting the world know who he or she is.

14. Week Fourteen

At week fourteen, the baby starts to “sit” upright and his or her neck is now longer. Growth of hair and eyebrows are possible although, of course, this is hardly visible. You’ll also be pleased to know that at this stage, the baby’s digestive and excretory systems are working well.

15. Week Fifteen

Three weeks into your second trimester, your baby’s body starts to resemble a human baby’s body. The best thing about this stage is that the baby starts responding to light! Even though his or her eyes are still shut, the baby becomes sensitive to light and even responds to it.

16. Week Sixteen

The baby’s interaction with the world at week sixteen becomes even more exciting. At this stage, bones that will become the baby’s ear fall into place and your baby can hear you! Your baby also has the capacity to make some facial expressions because bones and muscles on the face are starting to develop.

17. Week Seventeen

At week seventeen, everything that’s starting to form in your baby will develop at a much faster pace. The placenta becomes even more functional, giving your baby all the nutrients he or she needs. Eyes, nose, tongue, and most of the body are now clearly recognizable in a sonogram. You’ll have a hard time hiding your excitement over your baby’s birth!

18. Week Eighteen

Your baby’s favorite activity during the eighteenth week will be opening and closing his or her palms. Since the baby is still in the womb, there will be lots of times when she or he clings to the umbilical cord. Genitals and teeth also start forming at this stage, so if you want, you can ask your doctor whether you’re having a boy or a girl.

19. Week Nineteen

Sensory response and coordination are the main developments of your baby during the nineteenth week. Your baby’s skin and some cartilaginous body parts are also starting to form. In the early stage in the womb, babies are translucent, but they start losing that quality at this point.

20. Week Twenty

Movement starts to become more prominent halfway through your pregnancy. During your twentieth week, your baby is exploring skills and doing flips inside your womb. He or she is also learning how to swallow, truly preparing to become the growing kid he or she will soon be.

21. Week Twenty-One

At week twenty-one, your baby gets even more excited about tasting things because this is when taste buds start to fully develop and become functional. Yes, it is true that the baby eats what you eat, so at this stage, it is best to get him or her accustomed to the types of food you want him or her to eat.

22. Week Twenty-Two

Hormones and more movement characterize week twenty-two of pregnancy. Your baby is now starting to get used to his or her sense of touch, so your baby will want to move around a lot more. If you know pregnant women who say that their babies in the womb have their own schedule, they are probably at this point in their pregnancy.

23. Week Twenty-Three

At week twenty-three, fat is ready to form inside your baby’s body. Soon, the fact that a human being is growing inside of you will feel even more real. At this stage, your baby is also preparing to learn how to breathe in air the moment she or he is born. The best part about all this is that you finally get to hear a steady sign of life by using a stethoscope.

24. Week Twenty-Four

Upon entering week twenty-four of pregnancy, you should start bracing yourself. Your baby is growing faster than ever. Soon you’ll experience some back pains and difficulty moving because you’re carrying a live human being inside of you. Facial features start to become more pronounced and fat deposits fill the baby’s body.

25. Week Twenty-Five

During the twenty-fifth week, your baby’s nostrils start to open a bit more, preparing him or her for breathing. To carry oxygen throughout the body, your baby’s circulatory system becomes more functional. In an advanced sonogram, your baby starts to show amazing signs of life through color and movement.

26. Week Twenty-Six

If you’re having a boy, week twenty-six is very important. The baby’s scrotum starts to descend at this stage thanks to the continuous production of important hormones in the womb. His sense of sight and hearing is also starting to sharpen, so now is a good time to introduce him to sounds you’ll want him to remember.

27. Week Twenty-Seven

The brain activity of babies starts to heighten during the twenty-seventh week. All the movement and skills your baby has been trying out the past couple of weeks will become more evident at this stage. So, yes, prepare yourself for some intense action inside of you.

28. Week Twenty-Eight

During the twenty-eighth week, your baby takes on a position that will be crucial for when she or he leaves the womb. Some babies have their heads down in a vertical position, which is the ideal position for when the baby comes out. Sometimes the baby has his or her bum down; this is okay too, and there is nothing to worry about. At this point, some of your baby’s favorite activities will be sucking his or her thumb and coughing.

29. Week Twenty-Nine

For some moms, babies on their twenty-ninth week move non-stop. Thanks to the growth spurt of your baby’s brain and lungs, he or she is more active than ever. It will almost feel like you are in constant interaction with your baby. This is when it starts to become truly difficult yet special for moms-to-be.

30. Week Thirty

Even if your baby is born this early, she or he has a good chance of surviving because almost all development is complete. Brain activity is higher and the baby can follow light with his or her eyes. Of course, the baby will still become a bit heavier, but this is a good sign of a healthy, growing baby.

31. Week Thirty-One

During the thirty-first week, all your baby’s five senses are working together so well that he or she will start to remember what being inside the womb feels like. This is why some babies sleep better at night with white noise or anything that reminds them of their time in the womb. Your connection with your baby can only get stronger from here.

32. Week Thirty-Two

Even while inside the womb, babies already have a routine of their own. During the thirty-second week, your baby will make sure you are aware of his or her schedule and activities. When your baby is awake, she or he will do everything that she or he has learned to do inside your womb. You get to sleep when the baby sleeps, which is up to your baby. In a way, this is preparing you to become a mother raising a child.

33. Week Thirty-Three

Your baby’s skeletal system develops very interestingly during the thirty-third week. The bones of the rest of your baby’s body are becoming solid enough for birth, but the skull is still soft and has yet to fuse. This makes the baby’s passage through the birth canal easier, ensuring that she or he is delivered correctly.

34. Week Thirty-Four

Your baby’s antibodies and immune system become stronger during the thirty-fourth week of your pregnancy. Once your baby enters the world, he or she is exposed to all sorts of organisms, and your baby has to be ready for that. Now that your baby knows how to breathe, he or she also has the means to fight those things that he or she shouldn’t be breathing in.

35. Week Thirty-Five

All the little things that make your baby truly human are present during week thirty-five. Hair, nails, toes, and little fingers — all are moving and functional. Your baby’s nervous and immune systems are also preparing him or her for arrival into the world. Your baby is even blinking and is fascinated by all sorts of sounds and sensations!

36. Weeks Thirty-Six to Thirty-Nine

These last few weeks of pregnancy don’t see many drastic developments, but they are still very important. You could call these weeks a time for your baby to toughen up as birth approaches. All bodily systems are functioning well and your baby is learning how to respond to the real world. As your baby crosses early term to full term, his or her skin pigmentation becomes more apparent.

Your baby is also finding the best position to be in for when the time comes. Some moms are lucky that their babies find themselves in the right position for birth — in a vertical position, with their heads down. If this is not the case during week thirty-six, don’t worry; there’s still time for your baby to figure it out.

37. Week Forty

Congratulations! You did it. Your baby is ready to see the world! He or she has had nine full months to prepare for this moment, and now the time has come. The last parts of your baby to develop will be the fontanelles or two soft spots on your baby’s skull, which will adjust as the baby’s brain grows.

They say motherhood begins the minute your baby is born, but tracking your baby’s growth week by week will make you feel like you’ve already been a mother for nine months! If you think this time is truly special and magical, just wait until your baby becomes a child whom you’ll love no matter what. Despite the difficulty, pregnancy and motherhood are truly worth it.

Do you have any advice for pregnant moms-to-be? Let us know in the comments section below!

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