Fetal Development
Fertilization
Day 1 (Conception Day) – Sperm and egg join forming one cell. The fertilized egg has a normal quota of 46 chromosomes – 23 from mom and 23 from dad. These 46 chromosomes contain all of the genetic information for this individual's human development - gender, hair and eye color, height, skin tone.
First Trimester
Days 2 to 5 –The fertilized egg is now called an embryo. During this time the embryo travels down the fallopian tube to the uterus where the mucous lining has become soft to nestle and nourish this new life.
Days 6 to 10 – Implantation occurs around day 6. Hormones send signals to the mother’s body to nurture the embryo and prevent monthly periods.
Week 2 – The pregnancy hormone, hCG can be found in the mother’s urine by this time. A pregnancy test can measure this hormone determining pregnancy.
Day 18 to 21 – Before the mother’s period is one week late the embryo’s heart begins to beat. The brain is developing; the eyes, lungs, intestine and stomach are appearing.
Days 28 to 31 – The baby is now 10,000 times larger than the original fertilized egg (measuring 1/8 of an inch long) and is developing rapidly. The backbone, which protects the spinal cord, has formed. Arms, legs, eyes and ears have begun to show. The embryo makes his own blood and the heart beats 65 times a minute.
Day 35 – During this week the testicles or ovaries are beginning to form, depending on the baby’s gender.
Day 40 – Brain waves can be detected and recorded.
Week 6 – The baby is now ½ of an inch long. The eyes are wide open though eyelids and irises have not formed yet. Fingers have grown to the first joint, but are still webbed as are the toes.
Week 7 – The embryo begins to move. The jaw forms and teeth buds are in the gums. The mother is about to miss her second period.
Days 6 to 10 – Implantation occurs around day 6. Hormones send signals to the mother’s body to nurture the embryo and prevent monthly periods.
Week 2 – The pregnancy hormone, hCG can be found in the mother’s urine by this time. A pregnancy test can measure this hormone determining pregnancy.
Day 18 to 21 – Before the mother’s period is one week late the embryo’s heart begins to beat. The brain is developing; the eyes, lungs, intestine and stomach are appearing.
Days 28 to 31 – The baby is now 10,000 times larger than the original fertilized egg (measuring 1/8 of an inch long) and is developing rapidly. The backbone, which protects the spinal cord, has formed. Arms, legs, eyes and ears have begun to show. The embryo makes his own blood and the heart beats 65 times a minute.
Day 35 – During this week the testicles or ovaries are beginning to form, depending on the baby’s gender.
Day 40 – Brain waves can be detected and recorded.
Week 6 – The baby is now ½ of an inch long. The eyes are wide open though eyelids and irises have not formed yet. Fingers have grown to the first joint, but are still webbed as are the toes.
Week 7 – The embryo begins to move. The jaw forms and teeth buds are in the gums. The mother is about to miss her second period.
Week 8 – Now about 1 ½ inches long (40 millimeters), the embryo is now called a fetus - Latin for "young one" or "offspring." Everything is now present that will be found in the fully developed adult. The heart has been beating for a month. The stomach and kidneys have begun to function, and there are approximately 40 muscle sets beginning to function through the direction of the nervous system.
Week 9 – Fingerprints are evident.
Week 9 – Fingerprints are evident.
Day 35 – During this week the testicles or ovaries are beginning to form, depending on the baby’s gender.
Day 40 – Brain waves can be detected and recorded.
Week 6 – The baby is now ½ of an inch long. The eyes are wide open though eyelids and irises have not formed yet. Fingers have grown to the first joint, but are still webbed as are the toes.
Week 7 – The embryo begins to move. The jaw forms and teeth buds are in the gums. The mother is about to miss her second period.
Day 40 – Brain waves can be detected and recorded.
Week 6 – The baby is now ½ of an inch long. The eyes are wide open though eyelids and irises have not formed yet. Fingers have grown to the first joint, but are still webbed as are the toes.
Week 7 – The embryo begins to move. The jaw forms and teeth buds are in the gums. The mother is about to miss her second period.
Week 11 – The fetus is now 2 inches long. Muscle movements are becoming more coordinated. The umbilical cord brings blood so the baby can get oxygen.
Week 12 – All external body features have appeared: fingers and toes can be seen and genitalia are becoming distinguishable. The brain is fully formed, which some think, allows the baby to feel pain. The baby now has sleep and wake cycles. He exercises his muscles energetically, turning his head, curling his toes, opening and closing his mouth, and sucking his thumb.
Week 12 – All external body features have appeared: fingers and toes can be seen and genitalia are becoming distinguishable. The brain is fully formed, which some think, allows the baby to feel pain. The baby now has sleep and wake cycles. He exercises his muscles energetically, turning his head, curling his toes, opening and closing his mouth, and sucking his thumb.
Next: Second Trimester
Note: All information on this website is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your physician.
All pictures are used for illustration purposes only. The models are not connected to Cornerstone Women's Resource Centers or its services.
All pictures are used for illustration purposes only. The models are not connected to Cornerstone Women's Resource Centers or its services.
