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Pregnancy Week By Week

For even more information on “Counting 40 Weeks,” first, second, and third trimesters, and more—please read our How To Calculate Your Due Date resource on our website.

Weeks 1-2

Getting Things Ready

A lot is happening now, but you can’t see it with the naked eye. This is when your body is ovulating and your uterus is getting ready to possibly conceive by the thickening of the uterine wall and releasing an unfertilized egg.

Week 3

Here is the big moment. This is the week where ovulation and implantation can occur. When the one single sperm meets the egg, there you have it…conception. At conception, the fetus’s eye color, hair color, gender and more have already been determined.

Right now, the fetus is actually called an embryo and some major things are happening. The embryo’s brain, spinal cord, heart, and gastrointestinal tract are all being developed.

Week 4

Time to Take a Pregnancy Test

It’s now time to take a pregnancy test. Most women discover their pregnancies between weeks 4-7. Pregnancy symptoms may start to develop such as a missed period or breast tenderness. Since ovulation times are different for every woman, it’s important that you take a free, medical-grade pregnancy test and receive a free ultrasound so we can determine exactly how far along you are.

Your embryo is experiencing some major growth here. The beginning stages of the nervous system, skin, nails, hair, mammary glands, sweat glands and enamel for teeth begin to develop. Also, the foundations of the heart, lungs, skeletal system, liver and much more are being created. Even arms and legs begin to develop this week.

Week 5

Heartbeat!

Your embryo’s heartbeat is steady and the eyes and ears are forming but some women begin experiencing morning sickness this week.

Week 6

You may begin to experience more pregnancy symptoms by week 6. Heartburn, some slight cramping, and light bleeding are super normal this week. Your breasts may still be pretty tender and you might even notice that they make look a little bit darker than normal.

Week 7
Essential Organs, Eye Lids, and hair follicles. Your baby is now developing a tongue, hair follicles, and eyelids. Every essential organ that a human being needs to survive has already been forming at this point.
Week 8
Embryo Is About the Size of a Grapefruit

Your baby now contains every body part that an adult has but they are not fully developed. The facial features begin to become more defined, and their muscles are even able to contract.

Week 9
The fetus can also start sucking its thumb this week.
Week 10
Baby Starts Kicking! The fetus’s kidneys, liver, brain, and lungs are now functioning. Plus, fetuses start to kick their newly developed legs this week.
Week 11
Your body is continually changing along with the ever-changing fetus. Your fetus is very active at this point. The skeleton is beginning to harden and your fetus’ head is almost half of its entire length.
Week 12

Fetus’s Kidneys Develop

You are almost out of your first trimester at this point. Your ever-growing uterus is expanding. Your fetus is continually growing as well. Its kidneys can now secrete urine and the facial features become more recognizable.

Week 13

Your fetus now has its very own fingerprints.

Second Trimester: 14-27 Weeks

Week 14
Fetus Can Make Facial Expressions! Because of your fetus’s developing brain, it can now make facial expressions with its facial muscles. Its liver and spleen have also begun to develop more.
Week 15
You can actually see your fetus’s skeleton on an x-ray if it were taken this week.
Week 16

“Pregnancy Glow”

You may be experiencing that “pregnancy glow” due to the increased blood volume and overactive oil glands. Your fetus’s circulatory and urinary systems are beginning to function now, along with some other body systems.

Week 17
Fetus Begins to Develop Hearing. Most women see a noticeable baby bump by now. Your other internal organs begin to make room for your growing uterus. Your fetus’s hearing is beginning to develop.
Week 18
Your fetus’s genitals are beginning to form externally now. It is typically possible to distinguish whether it’s a male or female on ultrasound by this point.
Week 19
Fetus Develops Hair. As other parts of the fetus’s development continue, hair is beginning to grow on the fetus’s head.
Week 20

Halfway Through!

You made it halfway through your pregnancy! Yay! Typical weight gain at this point is between 8-10 lbs.

Week 21
Digestive System Develops. Your fetus is now swallowing amniotic fluid and the digestive system is continuing to develop.
Week 22-23
Your fetus is beginning to gain weight rapidly and looks more and more like a newborn baby.
Week 24
Fetus’s Brain Developing Quickly. Your fetus’s brain is developing quickly. It is also beginning to develop taste buds during this time.
Week 25

Boy Or Girl?

Right now, the uterus is about the size of a soccer ball. Your fetus’ gender should be distinguishable with ultrasound by now (or even before).

Week 26

Lungs Developing and Responds to Sounds. Your fetus’s lungs are continuing to develop and it is actually able to respond to sound.

Week 27
Fetus Can Open Eyes & Hiccup. Your fetus may be able to open its eyes at this point and now has a regular sleep and wake cycle. Let’s just hope it’s the same as yours!

Third Trimester: 28-40 Weeks

Week 28
You’re In the Home Stretch! Your fetus is continuing to gain weight and has eyelashes and eyebrows.
Week 29
Brain Growth Continues – Stay Healthy! The fetus is experiencing some pretty amazing brain development. Make sure to continue to eat foods that are high in folic acid and other vitamins. Plus, continue taking those prenatal vitamins.
Week 30
The fetus is continually growing and now able to distinguish between light and dark inside the womb.
Week 31
Your fetus is continuing to gain weight and develop its lungs.
Week 32

May Experience Braxton Hicks Contractions

You may experience Braxton Hicks contractions during this time. They are completely normal and it’s your body’s way to “practice” labor. If you are not aware if you are experiencing Braxton Hicks contractions or real labor, contact your doctor.

Week 33
Fetus’s Bone Hardening! Your fetus’ bones are all beginning to get hard (except for the skull which needs to remain moldable for delivery).
Week 34
Body Preparing for Delivery – Fetus Central Nervous System Developing. Your fetus’ central nervous system is still developing and it’s still gaining a consistent amount of weight.
Week 35
The fetus is pretty much done growing by this point. It will continue to gain weight but the kidneys have totally developed. Since there is less room for the fetus to kick, you should still be able to feel it move consistently.
Week 36-37
Most fetuses at this point are head down toward the pelvis. Getting close to delivery! Your fetus is continually enjoying its womb for the time. But the move-out day is approaching!
Week 38
All of the fetus’ organs are fully functioning (except the brain and lungs which continue to develop after birth).
Week 39-40
Your fetus is still gaining weight and now is at full term! You and your doctor have probably already talked about birthing possibilities and what to do if you go over 40 weeks. Your pregnancy has been a continual journey of preparation for labor. Most full-term babies are between 19-21 inches long and weigh between 6 ¾ – 10 pounds.
Citations

Johnson, T. C. (2020, May 15). Pregnancy timeline: Fetal development week-by-week with pictures. WebMD. Retrieved February 16, 2022, from shorturl.at/bBZ23