FETAL DEVELOPMENT

Fetal Development

Fetal Development

Normal events of fetal development

From the 8th week of pregnancy until birth (around 38 weeks), the developing organism is called a fetus. The fetus is not as sensitive to damage from environmental exposures as the embryo. The majority of structures are already formed in the fetus, but they continue to grow and become functional.

Week One: The egg and sperm meet in the mother's fallopian tube. In a process known as conception (or fertilization), the two combine into a single cell. In this single cell, the gender (male or female) of the individual has already been determined. The baby now has all the genetic information he will ever have: a unique combination of 46 human chromosomes resides in this single cell, half of them from the egg and half of them from the sperm. For the rest of his life, nothing new will be added to his makeup, only nutrition and oxygen. Cell division begins about a day after conception. By the time this new individual burrows into his mother's uterine lining (a process known as implantation) at 7-10 days after conception he will have grown from a single cell into 128 to 256 cells.( Wilcox AJ, 1999 )

18-25 Days: The baby is only 1/100 of an inch long, but his tiny heart is already beating. By the 20th day, the foundation for the nervous system is laid down.

Week Four: By now, blood circulation is well-established. The larynx and inner ear are beginning to form, as are the legs and arms. The liver, pancreas, lungs, and stomach are also forming. By this point, the baby is 4-6 millimeters long from head to rump.

Week Five: The baby is now about 7-9 mm from head to rump. In the process of developing, the baby will go through three sets of kidneys. This week, the last set of kidneys appears.

42 DAYS: The skeleton is complete and reflexes are present. Brain waves (the presence or absence of which are used as a legal means to declare a born person living or dead) can be detected.( Prechtl, 2008)

Week Ten: The baby's brain now has the same structure it will have at birth. Within the next week, all body systems will begin functioning.

Week Fourteen: Mothers who are very thin or who have already had children might be able to feel the baby move by now. First-time mothers may not feel the movements for another 6-8 weeks. Using ultrasound, the baby's gender may be detected.

Week Fifteen: The baby weighs about 142 grams (5 ounces). Loud noises might startle him.

Week Seventeen: Girl babies will now have primitive egg cells in their ovaries. The buds that will become the permanent teeth have formed behind the baby's milk teeth.

Week Twenty-Four: Four out of 10 babies will live if born now.

Week Twenty-Seven: The baby urinates about a half liter of urine everyday. Mothers may notice smaller movements such as those of the baby's elbow and knees.

Week Thirty-Eight: Now the baby is ready to be ...