Fertilization: Day 1: Life Begins
- Life begins when the sperm and ovum (mature egg) unite to form a single cell (zygote, or fertilized egg)¹.
- 23 chromosomes are from the male and
- 23 chromosomes are from the female.
- The combined 46 chromosomes are now a zygote.
- This zygote is unique.
- It is a cell which never existed before.
- This cell has the genetic blueprint for eye color, gender, intelligence, height, hair color, skin tone, facial features, body type and personality characteristics.
- THE EMBRYO: 3-5 days after fertilization, the zygote becomes an embryo.
- The embryo travels down the fallopian tube and
- enters the uterus to implant into the uterine wall.
Week 2 – Embryo Growth
- The embryo implants into the uterine wall by the seventh day.
- The embryo begins to draw nutrients.
- Now hormones prevent the menstrual period (for most pregnant women).
Week 3 – Embryo Growth
- The brain, spinal cord, and nervous system begin to develop.
- The growing backbone causes the body to curl.
- The beginning of future organs are visible.
- The heart is formed.
- The heart beats around day 20.
Week 4 – Embryo Growth
- Simple kidneys, liver, and digestive system form.
- Arms, legs, eyes, and ears form.
- At 28 days old, this embryo is 10,000 times larger than the original fertilized egg.
Month 2 (Week 8) The Fetus
- The beating heart is visible on an ultrasound monitor.
- Brain waves can be recorded as early as 40 days.
- Impulses begin to control and regulate circulation, digestion, and waste elimination.
- Facial features are beginning to form: eyes, ears, lips, tongue.
- The jaw forms, including 20 tiny tooth buds in the gums.
- The eyelids seal to protect the light-sensitive eyes.
- At 8 weeks the embryo becomes a fetus (Latin word meaning “Young one.”)
- Elbows and fingers are now evident.
- The fetus is a half an inch in length.
- Everything is now present that will be found in a fully-formed and developed adult.
- The heart has been beating for more than a month.
- Immature lungs, kidneys, liver, brain, nervous system and digestive system are present.
- Forty muscle sets have begun to operate in conjunction with the nervous system.
- The fetus is capable of responding to touch.
Month 3 (Week 12) Fetal Growth
- The fetus is an average length of 2 inches.
- The soft, bony limb tissue now begins to calcify.
- The fetus has a routine: sleeps, wakes, exercises.
- Other developments:
- Curls its toes
- Turns its head
- Opens and closes its mouth
- “Breathes” amniotic fluid
- The iris of the eye is developing.
- Fingers and toes are forming, and fingernails begin to appear.
- The fetus has fingerprints, a unique identity that will identify him or her for the rest of its life.
- The fetus will move away if touched.
- Grasps fingers around an object
- If the palm is stroked, the fetus will make a tight fist.
- The fetus is able to experience pain.
- Sexual differentiation is apparent.
- All organic systems are functioning.
- The fetus has skeletal structure, nerves, and circulation.
- The fetus can now yawn and suck.
- The fetus can cry, and tries to do this in the uterus at times.
Month 4 (Week 16)
- The heart is beating. (It pumps 25 quarts of blood a day.)
- The ears are functioning.
- There is strong evidence that the fetus can hear quite a bit, including its mother’s voice and her heartbeat.
- The pregnant woman reports feeling movement within.
- The fetus is nourished an hour or two after the mother eats.
- The fetus can now urinate and swallow.
- By the end of this month the fetus is 7 inches in length.
- At 16 weeks the gender of the fetus can be seen on ultrasound.
Month 5 (20 Weeks) “Quickening”
- The fetus is approximately 12 inches long and weighs approximately one and a half pounds.
- The fetus curls when the mother moves and stretches out when the mother rests.
- Some pregnant women report being able to feel and sense this movement.
- Fetal movement felt by the pregnant women is called “quickening.”
- The female fetus now has a uterus and ovaries containing eggs.
- Loud noises may startle the fetus and cause him or her to jump in response.
- At this point the fetus rests when the mother rests.
- This is the halfway point of pregnancy.
Month 6 (Week 24)
- Vernix (white, waxy ointment) covers the fetus’ skin as protection.
- The skin is pink, translucent and wrinkly.
- Rapid eye movements are noted.
- The fetus has a blink-startle response if stimulated by loud noises.
- If born now (prematurely), and given the proper care, survival is possible.
- The lungs are well-developed and nearly ready to work.
- Hair is now visible.
- Unborn males have testicles which are ready to descend from the abdomen to the scrotum.
- From week 22 to week 32, the fetus experiences pain more intensely than at any other time in development.
- At 24 weeks, the fetus weighs slightly more than a pound.
Month 7 (Week 28)
- Hearing, vision, taste, and touch are in process.
- Eyelashes are clearly visible and the eyes begin to open.
- The fetus has fully-functioning taste buds on her or his tongue.
- Now the fetus can experience motion and do flips in the womb.
- The fetus can suck its thumb.
- The fetus now weighs approximately 3 pounds and is approximately 11 inches in length.
- If born at this age, the fetus can breathe air on its own.
- The brain is developed enough to coordinate rhythmic breathing and regulate its body temperature.
- Pregnant women report Braxton-Hicks Contractions at this point. These contractions occur in the third trimester (month 6-9 or weeks 24-36) and prepare the pregnant woman for childbirth.
Month 8 (Week 32)
- The fetus’ skin thickens and stores a layer of fat for insulation and nourishment.
- Antibodies form to give protection from disease and give immunity.
- The heart is now pumping 300 gallons of blood a day.
- The fetus absorbs a gallon of amniotic fluid per day and completely replaces that fluid every three hours.
- The fetus now has definite, active cycles of sleep and wakefulness.
Month 9 (Week 36 weeks to Week 40)
- The fetus is now 20 inches in length.
- Its body is more plump.
- The fetus has a firm grasp.
- Approximately one week before the 260th day, the fetus stops growing and drops its head downward into the pregnant mother’s pelvic cavity, preparing for birth.
- The average pregnancy is 280 days from the first day of the pregnant woman’s last period.
- Most babies are born between 266 and 294 days.
- They weigh between 6 and 9 pounds.
- The fetus is capable of living outside of the womb.
See: Images of Early Development