Prenatal Developement

Not long ago, the first nine months of human development were a mystery to all. Only in recent years have scientific and technological advances allowed us to directly observe life as it develops within the womb. We now know in great detail how the unborn fetus looks, acts and grows.Day 1: Conception Day: The egg and sperm most often unite in the fallopian tube (tube from the ovary to the uterus) to form a single cell called a zygote. The new life has inherited 23 chromosomes from each parent, 46 in all. This tiny new cell, smaller than a grain of salt, contains all the complex genetic blueprint for every detail of human development – the baby’s sex, hair and eye color, height and skin tone.
  • Day 6 – 10: (after conception) The embryo (developing fertilized egg) begins to implant in the lining of the uterus. Once this occurs, hormones trigger the mother’s body to sustain the pregnancy and prevent her monthly periods. The embryo around day 8 is about the size of the “period” used in this sentence (or 0.1 mm).
  • Day 21: The heart begins to beat.
  • Week 4: By now, the embryo is completely attached to the lining of the uterus. There is enough of the pregnancy hormone (hCG) circulating in the mother’s blood to give a positive pregnancy test.
  • Week 5: The foundation for every organ system is already established and beginning to develop. At this age, the first signs of brain development are evident, and the ribs, vertebrae and muscles begin to form. The developing lungs are evident, and the beating heart can be seen on ultrasound.
  • Week 6: At this stage, the origin of the entire central nervous system (brain and spinal cord) is laid down. The jaws and upper limb buds are now visible. By the end of week 6, the lower limb buds can also be seen.
  • Week 8: At a little more than an inch long, the developing life is now called a fetus – Latin for “young one.” 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. Forty muscle sets begin to operate in conjunction with the nervous system. The fetus’ body responds to touch, although the mother will not be able to feel movement until the fourth or fifth month.
  • Week 9: Fingerprints are already evident in the skin. The developing ears and nose are visible and there is pigment in the retina.
  • Week 11: At this stage of development, the fetus is about two inches long. During the next several weeks, the baby’s body will grow rapidly, and the tissues and organ systems will continue to mature and differentiate. The eyelids are fully formed and closed to protect the developing eyes. The baby can yawn and suck.
  • Month 4: By the end of this month, the fetus is eight to ten inches in length and weighs 8 ounces or more. 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. You can see the beginnings of the fingernails and toenails. The baby is coordinated enough to find its thumb and suck it.
  • Month 5: Half the pregnancy has now passed, and the fetus is about 12 inches long. The mother can definitely feel movement by now. If the baby is female, her uterus is already formed and her ovaries contain eggs. If the baby is male, his testicles are fully formed and are beginning to descent from the abdomen to the scrotum.
  • Month 6: Oil and sweat glands are functioning. With the support of intensive care, a baby born at this state is capable of breathing air, and the brain is developed enough to coordinate rhythmic breathing and regulate body temperature. The eyelashes are clearly evident, and the eyes begin to open.
  • Month 7: The baby now uses the four senses of vision, hearing, taste and touch. He can recognize his mother’s voice.
  • Month 8: The baby, now about 19 inches long from head to toe and weighing about 5 pounds, continues to grow and mature. The skin begins to thicken, with a layer of fat stored underneath for insulation and nourishment. Antibodies increasingly build up. The head is covered in hair and the fingernails have reached the tips of the fingers. The baby has active sleep and wake cycles.
  • Month 9: Toward the end of this month, the baby is ready for birth. The average duration of pregnancy is 280 days from the first day of the mother’s last menstrual period. Most babies are born somewhere between 266 and 294 days. The baby is now roughly 20 or more inches long and weighs between 6 to 9 pounds. Typically, the baby is head down in the mother’s pelvis and awaiting birth.