Stages of Fetal Development


About two weeks from the first day of your last period, ovulation occurs. Once the sperm has penetrated the egg, the egg shuts down, admitting no more sperm.

Now your baby has more than 200 genetically-determined characteristics such as sex, eye color, and hair color. Your baby is at the zygote stage and has half of their genetic makeup from you and half from their father. Over the next five days, the new life travels down the fallopian tube and implants in the lining of the uterus.
Once the baby is successfully implanted, it starts making pregnancy hormone β-hCG, giving you a positive pregnancy test.

First Trimester

The weeks of pregnancy are determined from the first day of your last period:

Week 4 – Positive pregnancy test

Week 5 – Brain, spinal cord, and heart begin to develop

Week 6 – Neural tube that will become the spine closes and the heart is pumping blood

Week 7 – Nostrils and eye lenses start to form

Week 8 – Brainwave activity begins and the baby’s arms and legs have grown longer

Week 9 – Elbows and toes can be seen and all the internal organs are forming
Week 10 – Breathing movements begin but the baby still gets oxygen through the umbilical cord

Week 11 – Facial features develop

Weeks 12-14 – Baby makes its own blood cells, can form a fist and is developing tooth buds. The nose and lips are completely developed.

Second Trimester

Weeks 15-18 – Baby will suck its thumb and kick and now has fine hair. The intestinal tract is functioning.

Weeks 19-21 – Baby can hear you singing and talking and can feel pain. Fingernails are almost fully grown. You can feel your baby move.

Weeks 22-25 – Baby has eyelashes and fingernails and is very active. The bone marrow is making blood cells, and the lungs are developing but do not make surfactant which is necessary for the baby to breathe outside of the womb.

Weeks 26-28 – Baby’s hearing and sight are completely developed now. Your baby can now create tears. If born at this time, your baby would have an 85% survival rate.

Third Trimester

Weeks 29-31 – Rhythmic breathing and body temperature are now controlled by the brain. The lungs are capable of breathing air, although medical help may be needed.

Week 32-34 – Baby has eyes that are open during alert times and closed during sleep. Almost all babies born at this stage of growth will survive.

Week 35-37 – Baby weights about 5.5 pounds at this stage. Muscle and bones are fully developed.

Week 38-40 – Your baby could be born any day now. At the time of birth, a baby has more than 70 reflex behaviors, which are automatic behaviors necessary for survival.

If you are considering an abortion, you have the right to have all your questions answered before making any decisions. This fetal development information will allow you to understand the growth of your baby through each stage of pregnancy.

If you have any other questions or would like to learn more about the options you have, please contact one of our clinics to make an appointment. To learn about available support, please visit our parenting page.

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