Week 1
The male's sperm unites with the female's ovum at fertilization. The resulting cell is a zygote, containing all of the
genetic information of the new human, uniquely combined from the mother and father. The zygote quickly divides, and the cells multiply.
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Week 2
The zygote forms into a ball of cells called a blastocyst. The outer cells will form the placenta.
The new embryo anchors, or implants itself, to the uterus.
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Week 3-4
The placenta forms to provide the embryo with nourishment. The embryo's heart begins beating with its own blood, sometimes
a different type than either parent. The spine, nervous system, and internal organs begin to form. Small balls of cells
that will grow into the baby's muscles and bones appear. At 4 weeks, sensory cells begin to form eyes, ears and nose, and
arms start to bud out.
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Week 8
This is the last week for the baby to be called an embroyo. After this he or she is termed a fetus—Latin for "young one." Fingerprints are forming,
the baby begins to hear, and her responses to stimuli increase.
All organs are present. They will mature through the rest of the pregnancy. Cartilage begins to be replaced by bone.
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Week 9-12
The baby's teeth and fingernails start to form. Baby boys begin producing testosterone. Genital organs are recognizable.
The fetus can make a tight fist, and she can suck her thumb. She begins to make urine.
You may be able to feel when she kicks or hiccups.
See the perfection of the baby's feet and legs in these photos at 11 and 12 weeks. Notice how translucent the skin is at this point.
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Week 13-16 (Month 4)
From week 13-16 the fetus will grow from about 3 inches to 6 inches long. Her muscles are getting longer and her bones are hardening.
Her eyebrows and eyelashes develop.
By now she can hear her mother's voice and other sounds, and she can feel pain.
You can usually feel the baby's movements as she grows bigger and stronger.
By the end of week 16, her heart is pumping 25 quarts of blood per day.
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Week 17-20 (Month 5)
By week 17, the baby can dream. By week 20 she is recognizing her mother's voice. A fine hair called lanugo covers her body. Sex organs become more obvious.
Notice the eyebrows, hair and fingernails on the five-month-old babies shown.
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Month 6
The baby's skin turns from almost transparent to opaque. Oil and sweat glands develop, and a waxy substance
called vernix protects the skin.
Her brain matures and reflexes develop, including the
reflex to startle at sudden loud noises.
She practices breathing by inhaling amniotic fluid.
By the end of the sixth month, the baby weighs around two pounds and can be up to 12 inches long.
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Amillia Sonja Taylor (above) was born at a mere 21 weeks and six days on October 24, 2006. At birth she weighed under 10 ounces and was 9-1/2 inches long. She spent 4 months in the hospital before she got to go home.
The photo below shows her later.
Month 7-9
The baby's brain develops quickly during this period. Her skin thickens, and she develops a layer of subcutaneous "baby fat" to
insulate her and store up nourishment. She can open and close her eyelids.
The baby's likelihood to survive birth jumps from 60% at 25 weeks to 90% just three weeks later. Just before birth her heart pumps 300 quarts
of blood every day.
During the last few weeks before birth, the average baby reaches 7 to 8 pounds and a length of 14 to 20 inches. The baby is running
out of room, as you can see in the picture of this 8-month-old boy. When the baby is ready, she triggers labor, and the mother's body delivers her.
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More Information
For more infomation, visit these resources, from which the information on this page was compiled:
Fetal Development -- From Conception to Birth is a simple
presentation by the National Right to Life Committee.
Human Development in Utero - Physicians for Life
Embryology for K12 Students - University of New South Wales has very
detailed medical information on fetal development complete with photos at every stage. Dr. Mark Hill also explains and illustrates
the Carnegie stages of development as they apply to humans and babies of other species.
Fetal Development - Westside Pregnancy Resource Center is clear and easy-to-understand with excellent color photos.
Embryoscopy and Fetoscopy - Stand Up Girl
Prenatal Development - Abort73.com
Cesarean Voices - Babies are Conscious. David Chamberlain, PhD, shares details about the physical, mental, and emotional development of babies in the womb.
Mayo Clinic - Fetal Development: The First Trimester
The photos on this page are taken from the above sites. Those from the National Right to Life Committee are used by permission.
All others are included for educational, non-commercial purposes under fair use guidelines.
