Fetal Development

First Trimester (0-13 Weeks)

Day 1

The first day of your pregnancy begins on the first day of your last menstrual period.

2 Weeks

Your baby is made when the egg and sperm meet. This creates a new cell called a zygote which contains all the genetic information your baby will every need including eye color, gender, and even fingerprints!

4 Weeks

By the time you miss your period you are about 4 weeks pregnant! Your baby is now completely attached to the lining of your uterus wall. This allows the baby to get the nutrients it needs to continue to grow.

5 Weeks

Your baby’s heart has begun to beat, and the baby’s brain is showing development! Every organ system the baby will need to survive has already begun to develop!

6 Weeks

Your baby’s eyes have begun to develop and leg buds and arm buds have begun to appear. Her beating heart can already be seen on an ultrasound! Your baby is about 1/6th of an inch long.

8 Weeks

Your baby’s lungs are developing, and taste buds and tooth buds have begun to form. Your baby is now 1/2 inch long.

10 Weeks

Your baby’s brain is growing so rapidly that every minute it is producing about 250,000 neurons (nerve cells that transmit electrical signals across the body). The outside of the baby’s ears are now developed. The baby is about 1 1/4 inches long.

12 Weeks

Your baby’s fingers and toes are distinct and even have nails! Your baby is now moving, although it is too early to be felt. Your baby is now about 2 1/2 inches long.

Second Trimester (14-27 Weeks)

14 Weeks

Your baby can now swallow and her kidneys are making urine. She can even suck her thumb! Your baby is now 3 1/2 inches long.

16 Weeks

You might be able to see the gender of your baby on an ultrasound! Some women will be able to feel their baby move by now. Your baby is now 4 3/4 inches long.

18 Weeks

Your baby has REM cycles which means she is already dreaming! She even has her own unique set of fingerprints which she will carry with her throughout her life! Your baby is now 5 inches long.

20 Weeks

Your baby can feel pain. She has respiratory movements and all of her organs are formed. Your baby is now 6 1/4 inches long!

22 Weeks

Your baby has visible hair! There is little chance before this time that she might able to survive outside the womb now with intense medical care. Your baby is now 7 1/2 inches long.

24 Weeks

Your baby can hear your voice, your breathing, and even your heartbeat! The lungs have developed enough that your baby may be able to survive outside the womb with intensive medical care. Your baby is now 8 1/4 inches long.

26 Weeks

Your baby can taste your amniotic fluid and tell whether its sweet, sour, or bitter! Your baby’s eyelashes and eyebrows are formed. Not only can she hear you, but she can hear other noises outside your body as well. She can even respond to light! Your baby is now 9 inches long.

Third Trimester (28-40 Weeks)

28 Weeks

Your babies eyes are partially opened. Her brain is developed enough to regulate her body temperature and help her breath rhythmically. 9 out of 10 babies born at this stage will survive with intensive care services. Your baby is now 10 inches long.

30 Weeks

Your babies lungs can breathe air, but some medical help may be required. Your baby can open her eyes and even cry. Almost all babies born at this point will be able to survive with intensive care. Your baby is 10 1/2 inches long.

32 Weeks

Your baby can remember music that she hears every day! She might even start moving to the beat! Your baby is now 11 inches long.

34 Weeks

Your baby’s skin is pink and smooth. Her eyes are wide open, so she may respond more to light at this stage. Your baby is 11 3/4 inches long.

36 Weeks

Your baby is rounding out and gaining weight. She can recognize your voice and be comforted by it. Almost all babies born at this stage will live. Your baby is now 12 1/2 inches long.

38 Weeks

Your baby has a firm grasp. She continues to suck her thumb, which helps prepare her for breastfeeding. Your baby is now 13 1/2 inches long.

40 Weeks

Your baby is full term and ready to be delivered. She will usually be head down in your pelvis waiting to be born. Your baby about 14 inches long which makes her about 20 inches overall! She will weigh about 6 1/2 to 10 pounds.

 

*All measurements are from head to rump. The baby’s legs are not included in her length measurement.

 

Resources:

-Vicki L. Dihle, PA-C and Bradley G. Beck M.D. The First Nine Months. Focus on the Family, 2010. Brochure.

-Louisiana Department of Health and Hospitals. Abortion Making a Decision.Department of Health and Hospitals/Office of Public Health. Booklet.

-Heritage House ’76, Inc. 800 858-3040. Earn While You Learn Curriculum, Lesson 3.3 Your Unborn Baby’s Secret World. Print.