Each Day Matters

Pregnancy is a time of incredible transformation for mom and baby. Over the course of about nine months, a fertilized egg transforms from a tiny bundle of cells into a baby who is ready to meet the world. At the same time, your body adapts to meet the demands of your growing baby.

While modern NICUs are wonderfully equipped to care for preterm babies in the event of an early delivery, there is no doubt that the womb is natures preferred environment to nurture a growing fetus. By studying outcomes for preterm babies, scientists have learned that each week of development in the uterus translates into better survival rates and less time in the hospital.

baby laughing while laying on the bed

Explore your baby’s development, week by week:

1st Trimester
2nd Trimester
3rd Trimester
8 week digital image of a baby in the womb
8 weeks

What’s happening in the baby’s body: Baby’s facial features are beginning to develop. And while you won’t be able to feel it, your baby will start to make small movements this week.

What’s happening in mom’s body: You may be feeling quite a bit of nausea this week. In addition, aversions and cravings are often associated with nausea. These symptoms are thought to be due to rising hormone levels in your body.

9 week digital image of a baby in the womb
9 weeks

What’s happening in the baby’s body: The muscular diaphragm is beginning to develop. This will eventually allow your baby to breathe and even hiccup. Baby’s brain waves are also now detectable.

What’s happening in mom’s body: Your breasts will begin to get bigger, which may be very noticeable during this week of pregnancy. This is due to the rising hormones in your body.

10 week digital image of a baby in the womb
10 weeks

What’s happening in the baby’s body: This week, baby has graduated from embryo to fetus. Your baby will be able to start making breathing movements as the diaphragm is now complete. Ossification is also beginning to occur, which is when baby’s bones begin to form.

What’s happening in mom’s body: Your uterus is growing larger, and you’ll probably notice it. It’s likely as big as a tennis ball, which is double its pre-pregnancy size. You may begin to feel discomfort in your pelvis as the surrounding ligaments and muscles begin to stretch.

11 week digital image of a baby in the womb
11 weeks

What’s happening in the baby’s body: Baby is starting to get more active, doing things like flexing fingers, rolling over, stretching, and hiccupping.

At this point, the umbilical cord is fully developed. This allows nutrients from your bloodstream to be carried to baby.

What’s happening in mom’s body: You may start to notice pimples or acne appearing on your skin. This is due to the increased level of hormones, including progesterone, in your body.

12 week digital image of a baby in the womb
12 weeks

What’s happening in the baby’s body: Your baby’s arms and legs are getting longer, and baby is beginning to develop muscle control.

What’s happening in mom’s body: You’ve entered the second trimester! At this point, many women notice that pregnancy symptoms such as nausea and fatigue begin to subside.

13 week digital image of a baby in the womb
13 weeks

What’s happening in the baby’s body: Baby’s bladder is hard at work! Baby is swallowing amniotic fluid, filtering it through the kidney, and passing it as urine about every 30 minutes.

What’s happening in mom’s body: You may notice that your waistline is expanding; however, it will probably be a few weeks before your belly appears noticeably pregnant to others.

Note: Be sure to talk to your doctor to see if the PreTRM Test is right for you.

14 week digital image of a baby in the womb
14 weeks

What’s happening in the baby’s body: It may be possible to identify the gender of your baby as its external sex organs are now visible.

What’s happening in mom’s body: Your body likely has more circulating estrogen, which helps improve the condition of your skin. Your skin is also receiving an increased supply of blood, helping to give you that “pregnancy glow.”

Note: Be sure to talk to your doctor to see if the PreTRM Test is right for you.

15 week digital image of a baby in the womb
15 weeks

What’s happening in the baby’s body: Your baby is likely moving around inside of you with more frequency and may be active for up to five minutes at a time. You might feel some slight fluttering – that’s baby!

What’s happening in mom’s body: At this point, you may notice a definite “baby bump”, rather than just an expanding waistline.

Note: Be sure to talk to your doctor to see if the PreTRM Test is right for you.

16 week digital image of a baby in the womb
16 weeks

What’s happening in the baby’s body: Your baby’s mouth can open and close now. This happens regularly and comes with actions such as swallowing, hiccupping, and yawning.

What’s happening in mom’s body: Your pelvic area likely feels heavy and firm at this point. This is because you have almost a cup of amniotic fluid in your uterus.

Note: Be sure to talk to your doctor to see if the PreTRM Test is right for you.

17 week digital image of a baby in the womb
17 weeks

What’s happening in the baby’s body: Your baby is likely bigger than the placenta at this point. Baby will continue to outgrow the placenta during your pregnancy.

What’s happening in mom’s body: With the placenta being fully functional, you’ll likely have more energy. Your uterus is growing and is most likely large enough to give you that noticeable baby bump.

18 week digital image of a baby in the womb
18 weeks

What’s happening in the baby’s body: Your baby is beginning to develop fingerprints on the pads of the fingers.

What’s happening in mom’s body: You may begin to feel slight movements from your baby. They will likely come as a fluttery sensation. These first feelings of movements are called quickening.

19 week digital image of a baby in the womb
19 weeks

What’s happening in the baby’s body: Your baby has developed visible eyebrows. Baby also now has tooth buds in place.

What’s happening in mom’s body: Your baby and uterus are growing inside of you and you’re probably feeling that added weight. This may lead to discomfort and back pain and may make it hard to stand for long periods of time. Don’t be afraid to take short breaks!

Note: This is the first week you can visit a qualified phlebotomy center to receive the blood draw for the PreTRM Test. Be sure to talk to your doctor beforehand to see if the PreTRM Test is right for you.

20 week digital image of a baby in the womb
20 weeks

What’s happening in the baby’s body: Your baby’s brain is developing and picking up electrical signals from its body. Your baby can sense things such as temperature and pressure.

What’s happening in mom’s body: Your abdominal muscles are being stretched and pushed apart as baby grows. This may cause a bulge in the middle of your stomach when you lie down and raise your head.

Note: This is the last week you can visit a qualified phlebotomy center to receive the blood draw for the PreTRM Test. Be sure to talk to your doctor beforehand to see if the PreTRM Test is right for you.

21 week digital image of a baby in the womb
21 weeks

What’s happening in the baby’s body: Your baby now has fat stored beneath the skin. This fat helps with growth and development.

What’s happening in mom’s body: You may notice that you’ve begun to develop “pregnancy brain,” causing forgetfulness and loss of concentration. While the cause of this is not known, doctors believe it may be due to the hormonal changes happening in your body.

22 week digital image of a baby in the womb
22 weeks

What’s happening in the baby’s body: Your baby’s hearing will begin to improve as the inner ear organs are maturing. They can now send nerve signals to the brain.

What’s happening in mom’s body: Now may be a time when you feel quite emotional. That’s totally normal. Talking to other moms-to-be or friends can help.

23 week digital image of a baby in the womb
23 weeks

What’s happening in the baby’s body: Your baby’s lungs are developing quickly. They aren’t quite ready for full use, but they’re getting there!

What’s happening in mom’s body: You may notice that you’re hotter and sweating more than usual. This has to do with the extra weight you are carrying and the increased volume of blood pumping through your body.

24 week digital image of a baby in the womb
24 weeks

What’s happening in the baby’s body: Your baby is probably yawning often now. This may be a way to regulate the amount of fluid or blood in the lungs.

What’s happening in mom’s body: You may have begun developing stretch marks on your skin. Exercising and eating nutritious foods can help you to maintain a healthy weight and reduce the amount your skin stretches. Moisturizing the skin can help to keep the stretch marks smooth.

25 week digital image of a baby in the womb
25 weeks

What’s happening in the baby’s body: Your baby is very flexible, and movements are beginning to get stronger.

What’s happening in mom’s body: You’ve now entered the third trimester! You may feel some discomfort as your uterus expands and your rib cage is pushed outward. Getting up and moving around can help ease the discomfort.

26 week digital image of a baby in the womb
26 weeks

What’s happening in the baby’s body: Your baby’s eyelids are open this week! Baby can even blink.

What’s happening in mom’s body: The volume of blood in your body is 50 percent higher than normal.

27 week digital image of a baby in the womb
27 weeks

What’s happening in the baby’s body: It’s likely that your baby now has a regular sleep cycle.

What’s happening in mom’s body: The hormonal changes in your body may be causing some pain in your pelvic joint at this point in your pregnancy.

28 week digital image of a baby in the womb
28 weeks

What’s happening in the baby’s body: A fluid with a jelly-like consistency sits in the umbilical cord to ensure it won’t become compressed as your baby moves around.

What’s happening in mom’s body: Back pain is normal at this point in pregnancy. This is due to the weight of your baby straining your abdominal muscles and your ligaments being softened by pregnancy hormones.

29 week digital image of a baby in the womb
29 weeks

What’s happening in the baby’s body: Your baby now has brain wave activity that researchers believe may contribute to your baby dreaming.

What’s happening in mom’s body: You may notice that your breasts are starting to produce colostrum and may leak from time to time. This is due to an increase in prolactin levels in your body.

30 week digital image of a baby in the womb
30 weeks

What’s happening in the baby’s body: Your baby is likely able to track and sense light because of developments in the retina. So, if you were to move a flashlight back and forth over your belly in a dim room, baby may react!

What’s happening in mom’s body: You may begin to feel Braxton Hicks contractions this week. They often occur after exercise or sex, or when you become dehydrated or tired.

31 week digital image of a baby in the womb
31 weeks

What’s happening in the baby’s body: Baby’s skin is beginning to look less translucent, and creases can be found in the skin of the wrists and the palms of the hands.

What’s happening in mom’s body: Some women experience ptyalism during pregnancy, which is when the body produces too much saliva due to an increase in estrogen. To combat this, try sucking on hard candies or drinking plenty of fluid to increase swallowing.

32 week digital image of a baby in the womb
32 weeks

What’s happening in the baby’s body: Your baby is beginning to grow hair on their head! Your baby is also shedding lanugo, which is a fine layer of hair that previously covered baby’s entire body. Lanugo is an important source of protein for baby so they will eventually swallow it in the amniotic fluid.

What’s happening in mom’s body: You’ll continue to gain weight at this point in your pregnancy, although the weight gain will slow down during these last few weeks.

33 week digital image of a baby in the womb
33 weeks

What’s happening in the baby’s body: It is likely that your baby is now in the head-down position. This position prepares baby for birth and allows blood to flow to the brain, which aids in development.

What’s happening in mom’s body: The top of the uterus, which is called the fundus, is high in your abdomen at this point. This is likely causing pressure under your ribs that makes it difficult to eat a full meal without feeling some discomfort.

34 week digital image of a baby in the womb
34 weeks

What’s happening in the baby’s body: Right now, your baby’s lungs are filled with fluid. This fluid will disappear once baby is born and takes their first breath.

What’s happening in mom’s body: At this point, your uterus has grown quite a bit and is putting pressure on your bladder. This may lead to leakage of small amounts of urine when you cough, sneeze, or exercise. This is called stress incontinence.

35 week digital image of a baby in the womb
35 weeks

What’s happening in the baby’s body: Baby is still working on maturing their nervous and immune systems. However, baby’s lungs are structurally complete, and the air sacs are creating a lubricant that will keep the sacs open when baby takes their first breath of air.

What’s happening in mom’s body: You might notice that your feet are getting larger, and your shoes don’t fit as well. This is due to your growing baby and the weight gain associated with your pregnancy.

36 week digital image of a baby in the womb
36 weeks

What’s happening in the baby’s body: Baby’s ability to hear sound is improving. They may even start turning towards familiar sounds, such as your voice.

What’s happening in mom’s body: Breathing and eating should become easier at this point as baby is descending into your pelvis. However, baby will likely be putting more pressure on your bladder so you may be running to the bathroom even more than before.

37 week digital image of a baby in the womb
37 weeks

What’s happening in the baby’s body: Bones in baby’s skeleton are beginning to harden. This process is called ossification.

What’s happening in mom’s body: You may begin to feel that your joints have loosened. This is due to the hormone relaxin, which causes the smooth muscles in your body to unclench.

38 week digital image of a baby in the womb
38 weeks

What’s happening in the baby’s body: Baby continues to add connections between neurons in the brain.

What’s happening in mom’s body: You may feel occasional new discomforts because your baby’s position is likely low in your pelvis. Staying active can help lift your mood and reduce discomfort.

drawing of a baby inside the womb
39 weeks

What’s happening in the baby’s body: Your baby is still gaining weight and doesn’t have a lot of room to move around.

What’s happening in mom’s body: You likely feel very large and uncomfortable at this point. Your uterus has pushed other organs out of the way and is taking up most of your abdomen and pelvis.

digital representation of a baby inside the womb
40 weeks

What’s happening in the baby’s body: Your baby is now fully grown! Right now, your baby is receiving antibodies from the placenta that will last until about six months after birth.

What’s happening in mom’s body: If you don’t go into labor this week, you will be induced, usually by week 42. Soon after your baby is born you will have additional contractions that will separate the placenta from the uterus wall. Your healthcare provider will then help deliver the placenta.

With any medical illustration the artist takes certain liberties to communicate relative growth of a very complicated 3D object in a color rendition 2D space. These images are meant to show relative changes and development and are not meant to be interpreted as true to life representations.

Learn More About Preterm Birth

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