Fetal Development

Conception

A mature ovum and sperm have united, each carrying 23 chromosomes.

The living, single cell is called a "zygote".

Three hours after conception, cell division begins.

By the fourth day there are 16 cells.

Implantation

This occurs approximately one week after conception.

The embryo produces a hormone that prepares the womb as a suitable environment.

Second and Third Weeks

The heart begins to beat between the 18th and 25th day.

All major organs are beginning to develop.

At 26 days the baby is 1/8" long.

Four Weeks

The mother's period is overdue by about one week...she may be suspecting her pregnancy

Five Weeks

The baby is now 1/3" long

Eyes have retina and lens

Blood is exchanged between mother & child

Six Weeks

The baby is 1/2" long

Facial features are visible

The mouth & tongue formed

Major muscle system developed

Eight Weeks

Name is changed from "embryo" to "fetus"

All organs are present, all that is needed is more time for them to mature.

The baby is 1" long

Fingers and toes are complete

Brain is complete

Baby is capable of feeling pain

Nine Weeks

Responds to touch by closing eyes or closing their hands.

Baby squints, swallows & retracts tongue

Twelve Weeks

Baby moves his/her arms & legs

Sucks thumb

Inhales & exhales amniotic fluid

The baby is 3-4" long; weighs 1/2 oz.

Vocal cords complete

The bones are beginning to calcify: cartilage is being replaced by hard bone.

12 weeks

16 Weeks

Genital organs clearly distinguishable

Able to grasp with its hands

The baby's swimming and kicking is not felt by mother

The baby measures 5 1/2", and weighs approximately 6 oz.

Fingerprints have formed

18 Weeks

Vocal cords working...can cry

The baby is 8" long

16 weeks

20 Weeks

Hair appears on head

The baby measures 12", and weighs one pound

Has a small chance of survival as pre-mature infant

Responds to noise

24 Weeks - 40 Weeks

The baby's eyes are sensitive to varying intensities of light and darkness.

Begins to gain weight rapidly, reaching an average of 7 1/2 pounds.

Growth takes place and averages 20" at the time of birth.

Around 36-38 weeks the baby descends head first into the pelvis in preparation for birth.

Birth takes place around the 40th week - the birth date is determined by the infant.