Prenatal Development

The life of a human child begins long before birth.

Your Life Began at the Moment of Fertilization!

Fertilization is the moment at which the sperm penetrates the ovum (egg) and the two unite.

Once fertilized, he or she is called a zygote, a unique human being with its own genetic code distinct from mother or father. Forty-six chromosomes, 23 from the father and 23 from the mother, combine and predetermine all human growth, development, and physical characteristics of that human for the rest of its life.

After fertilization, if development on this unique human being remains unbroken, a child will be born nine months later.

30 hours after Fertilization

The picture on the right is the zygote only thirty hours after fertilization. Magnified here, he or she is no larger than the head of a pin. Still rapidly dividing, the developing embryo floats down from the fallopian tube towards the uterus.

6-8 Days After Fertilization

In the uterus, the embryo may float freely in the uterus for about 48 hours before implanting in the uterine wall. Upon implantation, typically about 8 days after fertilization, complex connections between the mother and embryo develop to form the placenta. After implantation, the fertilized ovum, called a blastocyst, releases hCG, a hormore that indicates to the mother’s body to suppress menstruation. At this point, a sensitive pregnancy test could indicate pregnancy to the mother, but it depends on the strength of the hCG hormone released by the child.

Week Three

While your mother probably did not know she was pregnant yet, your heart was already beating and sending your own blood throughout your body. Because of your uniqueness from your mother, you might even have a different blood type than your mother. You were very small, but yet rapidly developing. The brain is forming and dividing into its three primary sections.


Week 4

Arms and Legs are forming, along with the spinal cord and muscles.

In only four weeks, the embryo is already 10,000 times larger than the original fertilized egg! Can you do that?

Week 5

Five fingers are visible as wrists and hands have solidified. Permanent kidneys are present, along with eyes which have darkened in pigment.

Day 40

Brain waves are recordable!


Week 6

The brain begins to coordinate operations and the movements of muscles. The child reacts to stimuli and may be able to feel pain. The liver has taken over production of creation of blood cells.

Week 7

Facial features are visible, including the mouth, gums, jaw, and tongue. Even teeth buds have begun to appear in the gums.

The eyelids of the child now begin to close to protect the sensitive eyes. They will reopen around the seventh month. The major muscle system is developed, and the unborn child practices moving.

Week 8

Your unborn child is a little more than an inch long. At this stage, the developing life is often called a ‘fetus’- Latin for ‘young one’. The tiny person is protected by the amnionic sac, filled with fluid. Inside, the child moves gracefully.

Most structures of a fully formed adult are present in the fetus in the eighth week.

Week 10

Fingerprints are forming, along with fingernails. The number of connections between nerves and muscles has tripled in one week!

Week 12

Vocal chords are complete, and your child can and does sometimes cry (silently)! What an awesome baby you have! The fetus has urinated and has even begun to practice breathing with his or her own lungs. The fetus may suck his or her thumb. When an object touches the palm, the fetus can wrap his/her hand around the object!

Week 14

The fetus is now 3 inches long and weighs almost an ounce. Sex differentiation is now apparent. The child's spontaneous movements can be observed: Muscles lengthen and become organized. You will soon start feeling the first flutters of the unborn child kicking and moving within.

15 weeks

The fetus has an adult's taste buds and may be able to savor the mother's meals.This little one is already sucking his thumb!

4th Month

By the end of this month, the fetus is eight to ten inches in length and weighs a half pound or more. The mother will probably start to "show" now. The ears are functioning, and there is evidence that the fetus hears the mother's voice and heartbeat as well as external noises. The umbilical cord has become an engineering marvel, transporting 300 quarts of fluids per day and completing a round-trip of fluids every 30 seconds.

5th Month

Half the pregnancy has now passed, and the fetus is about 12 inches long. The mother has definitely begun to feel movement by now. If a sound is especially loud or startling, the fetus may jump in reaction to it.

6th Month

Oil and sweat glands are functioning. The delicate skin of the growing baby is protected from the fetal waters by a special ointment called "vernix." If the baby were born in this month and given the proper care, he would survive.


7th Month

The baby now uses the four senses of vision, hearing, taste and touch. He can recognize the mother's voice.

8th and Early 9th Month

The skin begins to thicken, with a layer of fat stored underneath for insulation and nourishment. Antibodies increasingly build up. The baby absorbs a gallon of amniotic fluid per day: the fluid is completely replaced every three hours.


Birth in human beings typically occurs 270 days after conception, near the end of a full 9 months. This marks the end of the normal gestational period. Your child, now approximately seven and a half pounds and after nine months of developing, is ready for life outside the womb!

Shortly before birth (typically a few weeks for first births but sometimes only a few hours for later pregnancies), the child usually rotates into a head-downward position. This movement is referred to as "lightening" because it releases pressure on the mother's abdomen.

At birth the placenta will detach from the side of the uterus and the umbilical cord will cease working as the child takes his first breaths of air. The child's breathing will trigger changes in the structure of the heart and bypass arteries which will force all blood to now travel through the lungs.

The progression of the unborn child found here is a common scientific knowledge, though some information may change from study to study. Some wording is compiled from various sources, including Focus on the Family's The First Nine Months and the brochure Milestones of Early Life.