Overview of Fetal Development
By Sarah Terzo
Editor’s note. This appeared at clinicquotes.com.
Day 1: Sperm joins with ovum, to form one cell smaller than a grain 
of salt. The new life has inherited 23 chromosomes from each parent, 46 
in all. This one cell contains the complex genetic blueprint for every 
detail of human development – the child’s sex, hair and eye color, 
height, skin tone

day 21-25
 
Days 3 – 4: The fertilized egg travels down the fallopian tube into 
the uterus, where the lining has been prepared for implantation
Days 5 – 9: During this time, the fertilized egg implants itself in 
the rich lining of the uterus and begins to draw nourishment.
Days 10 – 14: The developing embryo signals its presence through 
placental chemicals and hormones, preventing the mother from 
menstruating
Day 20: Foundations of the brain, spinal cord, and nervous system are already established
Day 21: The heart begins to beat
Day 28: The back bone and muscles are forming. Arms, legs, eyes and ears have begun to show.
Day 30: At 1 month old, the embryo is 10,000 times larger than the 
original fertilized egg – and developing rapidly. The heart is pumping 
increasing quantities of blood through the circulatory system. The 
placenta forms a unique barrier that keeps the mother’s blood separate 
while allowing food and oxygen to pass through to the embryo.

day 37-40
 
Day 35:5 Fingers can be discerned on the hand. The eyes darken as pigment is produced.
Day 40: Brain waves can be detected and recorded

Week 6
 
Week 6: The liver is now taking over the production of blood cells, 
and the brain begins to control movement of muscles and organs. The 
mother is about to miss her 2nd period and has probably confirmed that 
she is pregnant.
Week 7: The embryo begins to move spontaneously. The jaw forms, 
including teeth buds in the gums. Soon the eyelids will seal to protect 
the embryo’s developing light-sensitive eyes, and will reopen at about 
the 7th month

week 7
 
Week 8: At a little more than an inch long, the developing life is 
now called a fetus – Latin for “young one” or “offspring.” Everything is
 now present that will be found in a fully developed adult. The heart 
has been beating for more than a month, the stomach produces digestive 
juices and the kidneys have begun to function. 40 muscle sets begin to 
operate in conjunction with the nervous system. The fetus’s body 
responds to touch, although the mother will not be able to feel movement
 until the 4th or 5th month.

Week
 9: Fingerprints are already evident in the skin. The fetus will curl 
its fingers around an object placed in the palm of its hand.
Week 10: The uterus has now doubled in size. The fetus can squint, swallow and wrinkle its forehead.

week 9-10
 

Week 10
 
Week 11: At this time, the fetus is about 2 inches long. Urination 
occurs. The face has assumed a baby’s profile, and muscle movements are 
becoming more coordinated

Week 12
 
Week 12: The fetus now sleeps, awakens and exercises its muscles 
energetically – turning its head, curling its toes, and opening and 
closing its mouth. The palm, when stroked, will make a tight fist. The 
fetus breathes amniotic fluid to help develop its respiratory system.
Week13: Fine hair has begun to grow on the head, and sexual differentiation has become apparent

14 weeks
 
Month 4: By the end of this month, the fetus is 8 to 10 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 quite a bit: 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 the round-trip 
of fluids every 30 seconds.

Week 16- 4th month
 
Month 5: 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

Week 20 (5th month)
 
Month 6: 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.

Month 7
 
Month 7: The baby now uses the 4 senses of vision, hearing, taste and touch. He can recognize his mother’s voice.
Month 8: 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 3 hours.

Month 8
 
Month 9: Toward the end of this month, the baby is ready for birth. 
The average duration of pregnancy is 280 days from the 1st day of the 
mother’s last menstrual period, but this varies. Most babies (85% to 
95%) are born somewhere between 266 and 294 days. By this time the 
infant normally weighs 6 to 9 pounds and his heart is pumping 300 
gallons of blood per day. He is fully capable of life outside the womb.
Source:  “The First 9 Months” Focus on the Family 1989
Source: NRLC News 
 
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