Milestones of fetal development

First Trimester – 1 day to 12 weeks

Day 1: Sperm joins with egg to form one cell no bigger than a grain of sugar. The new life has 46 chromosomes, 23 from each parent. The complete genetic blueprint is there: the child’s sex, hair color, eye color, skin tone and height. Everything is there, the baby just needs to grow, inside and outside the womb. The one cell continues to divide into two, four, eight, sixteen, thirty-two cells…
Days 5-9: The fertilized egg implants in the lining of the uterus to begin to get nourishment from the mother.
Day 10: The developing baby begins to produce a hormone that prevents the mother from menstruating.
Day 20: Foundations of the brain, spinal cord, and nervous system are established.
Day 21: The heart begins to beat.
Day 28: The backbone and muscles are forming. Arms, legs, ears and eyes have begun to show.
Day 30: At one month old the baby is 10,000 times larger than the original fertilized egg.
Day 35: Five fingers can be discerned in the hand. The eyes darken as pigment is produced.
Day 40: Brain waves can be detected and recorded.
Week 6: The liver is now taking over the production of blood cells and the brain begins to control movement of muscles and organs. Week 7: The baby begins to move spontaneously. The jaw forms, including teeth buds in the gums.
Week 8: The baby is a little more than an inch long. Everything is now present that will be found in a fully developed adult. Week 9: Fingerprints are already evident in the skin. The baby will curve its fingers around an object placed in its hand.
Week 10: The uterus has doubled in size. The baby can squint, swallow and wrinkle its forehead. Week 11: The baby is about 2 inches long. Urination occurs. Muscle movements are becoming more coordinated.
Week 12: The baby now exercises its muscles — turning its head, curling its toes, and opening and closing its mouth. The baby breaths amniotic fluid to help develop its respiratory system.

Second Trimester – 13 to 24 weeks

Week 13: Gender differentiation has become apparent.
Month 4: By the end of this month, the baby is 8 to 10 inches in length and weighs a half pound or more. The mother will probably start to “show.” The ears are functioning and can hear the mother’s voice and heartbeat, as well as external noises.
Month 5: The baby is about 12 inches long. The mother definitely has begun to feel movement.
Month 6: Oil and sweat glands are functioning. If the baby were born this month and given proper care, he/she would survive.

Third Trimester – 25 weeks to birth

Month 7: The baby now uses the four senses of vision, hearing, taste, and touch. She can recognize her mother’s voice.
Month 8: The baby’s skin begins to thicken with a layer of fat stored underneath for insulation and nourishment. Antibodies are increasingly building.
Month 9: Toward the end of this month, the baby is ready to be born. By this time he typically weighs between 6 and 9 pounds and his heart is pumping 300 gallons of blood per day.