A Timeline of Fetal Development: Weeks 1-12
- LC Medical
- Mar 19
- 3 min read
Let’s take a look at the timeline of fetal development that happens in Weeks 1-12 of pregnancy!
If you are recently pregnant, or plan to be soon, we’re here to walk with you through all 40 weeks of the pregnancy journey. In this blog, we’re looking at all the interesting and fun milestones your baby will experience in the first 12 weeks.
Week 1 - Menstruation
Many people may not know this, but the very first week of pregnancy actually begins with your LMP (last menstrual period). Menstruation is the beginning of your ovulatory cycle. After your period, the follicular phase of your cycle begins and your ovaries begin to grow an egg. The uterus starts to thicken and becomes ready for implantation.
Week 2 - Ovulation & Conception
Depending on the length of your cycle, your ovulation may occur later than Week 2, but every woman’s cycle is different, so you’re okay! During ovulation, the egg is released and travels down the fallopian tube. There, it meets the sperm and conception happens! Your baby’s DNA is created, and a new life is living inside of you!
Weeks 3 & 4 - Implantation & Formation
Once conception has occurred, the fertilized egg will travel back up the fallopian tube and implant itself to the wall of your thickened uterus. There, cells will form and begin dividing into your baby’s organs. In the meantime, an amniotic sac and a yolk sac are formed.
Weeks 5 & 6 - Heart, Mind & More!
In week 5 of pregnancy, two tubes will begin to form - one for the brain and spinal cord, and the other for the baby’s heart. About halfway through this week, the baby’s heart will already be beating! By week 6, the eyes, lungs, limb buds, and digestive system begin forming. The brain and spinal cord that began developing in week 5 are formed by now.
Weeks 7 & 8 - Limbs & Facial Details
At this point in fetal development, we can finally begin to see the body of your baby developing its shape. Tiny arms and legs begin to sprout, as well as the baby’s hair and tongue. Many of the little facial details are being formed, such as the eyes, nose, ears and upper lips. By the end of the 8th week, webbed fingers and toes can be detected at the end of each limb.
Week 9 - Movement!
By the ninth week, the limbs are nearly finished forming. Obviously, the arms and legs will continue to grow throughout the entire rest of the pregnancy, but the shape is finished at this stage. This is also an exciting milestone for your baby, because at this point in development, the baby will begin making movements on his/her own!
Weeks 10 & 11 - All the Details
In this stage of development, a lot of little things will happen to determine your baby’s features. Fingers and toes will no longer be webbed, and the fingerprints will begin to form. The baby’s facial profile will be well-defined, and his/her eyes will open! By the end of the 11th week, genitalia will begin to form and the baby’s fingernails will start to harden.
Week 12 - Give Us a Smile!
By week 12 of fetal development, the kidneys will be functioning and will start producing urine. And finally, we get to see the baby’s teeth forming!
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We hope you’ve learned something new today! So much happens in a baby’s first 12 weeks of life! Fetal development is such an interesting and beautiful thing to explore. If you would like to learn more about the first trimester of pregnancy, we would love to start an education plan with you!
If you or anyone you know is currently pregnant, LC Medical & Support Services is here as a cost-free resource! We offer hundreds of free classes about pregnancy, childbirth, maternal health & wellness, and more! Contact us today to learn about our education program and our other parental support services!
