Fetal Development

Welcome to your fetal development area! Here's where you can see what's happening with your baby week-by-week! Check out the videos that go along with your story to the right! Want a full overview? Try here! You can also page through the weeks below. See how your baby grows daily with our Pregnancy Calendar!

First Trimester:Weeks 1-4 | Week 5 | Week 6 | Week 7 | Week 8 | Week 9 | Week 10 | Week 11 | Week 12 | Week 13 | Week 14

Second Trimester:Week 15 | Week 16 | Week 17 | Week 18 | Week 19 | Week 20 | Week 21 | Week 22 | Week 23 | Week 24 | Week 25 | Week 26 | Week 27

Third Trimester:Week 28 | Week 29 | Week 30 | Week 31 | Week 32 | Week 33 | Week 34 | Week 35 | Week 36 | Week 37 | Week 38 | Week 39 | Week 40

1-4 Weeks Pregnant

Trimester: 
First

Go to: Week 5
Return to Fetal Development Overview

Ovulation occurs - The time is right; now you just need this egg to be fertilized!

Conception occurs - Did you know that during your pregnancy that your uterus will increase its capacity by 1000 times?!

Gender is determined - Immediately upon fertilization your little one is set as a boy or a girl. Ladies, this is one that you can't take credit for since it is up to the sperm to determine the sex of your baby. Sperm carries either a "X" (girl) chromosome or a "Y" (boy) chromosome. (*Hint:* You will have to hold off on picking out the pink or blue until at least the second trimester when the gender will be visible via ultrasound.)

• Implantation - Some spotting (also known as implantation bleeding) may occur about 10 - 14 days after conception. You may believe you are starting your period but generally this bleeding is extremely light and lasts only a day or so.

Neural tube forms at 1-4 weeks of your pregnancy - It will develop into the nervous system (Brain, spinal cord, hair, and skin). Already your baby has the foundation for thought, senses, feeling, and more!

• At 1-4 weeks pregnant, heart and primitive circulatory system rapidly form - While still in its beginning stages, this is the very life support system that will carry your child throughout his or her life.

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