Fetal development is an important component of overall child development. It can greatly affect an individual's psychological, emotional, and physical potential. Prenatal development of a child occurs in three distinct stages: germinal, embryonic, and fetal.
Stages Of Fetal Development: Germinal Stage (0-2 Weeks)
This stage begins at conception when a sperm and an ova merge in the fallopian tube. It yields a fertilized egg which is known as a zygote. After its creation, the zygote travels to the uterus, where it gets implanted for the rest of the pregnancy. 24 to 36 hours later, the process of further cell division called mitosis occurs, where the zygote starts dividing. Once the zygote divides itself into eight parts, the cells gain specific characteristics. The outer cells eventually become the placenta while the inner cells develop into the embryo.
This stage lasts from fertilization to 2 weeks. The cells become blastocysts made up of three layers. These layers eventually become different structures of the fetus's body. The ectoderm layer gets constructed into the skin and nervous system. The endoderm membrane ends up evolving into the digestive and respiratory systems. Lastly, the mesoderm morphs into the musculoskeletal system.
This stage also includes the process of implantation. Implantation is when the zygote attaches itself to the uterine wall. Implantation leads to hormonal changes that culturally signify the onset of pregnancy, such as nausea, changing appetite, food preferences, etc.
Stages Of Fetal Development: Embryonic Stage (3-8 Weeks)
The third week after successful conception marks the embryonic stage. In this stage, the previous zygote turns into a mass of numerous cells. It further develops and starts becoming distinctly human. In this stage, the zygote becomes the embryo.
This stage is significant due to the high proportion of brain development. Roughly four weeks after conception, the neural tubes begin developing. These tubes ultimately become the central nervous system, including the brain and the spinal cord.
Around the same time, the head, eyes, nose, ears, and mouth start developing. The blood vessel, which will finally become the heart, begins pulsing. In the fifth week, buds that will, in due course, become the arms and the legs materialize.
By the end of the embryonic period, around eight weeks after conception, the embryo develops the basic structures of the central nervous system and the peripheral nervous system. In this stage, cell differentiation is primarily finished.
Stages Of Fetal Development: Fetal Stage (9 Weeks- Birth)
The fetal stage begins around nine weeks and lasts until birth. In this stage, the developed embryo is called a fetus. The rough systems and structures formed earlier in the embryonic stage further develop. The neural tube evolves into the brain and the spinal cord. Neurons begin developing and creating networks.
Between the ninth and twelfth weeks of gestation, reflexes are acquired. Reflexes are involuntary movements. The fetus begins moving its arms and legs around this time.
In the third month of gestation, sex organs emerge. By the end of the third month, all parts of the fetus's body would have formed. The end of the third month signifies the end of the pregnancy's first trimester.
Stages Of Fetal Development: Beyond the three stages
The second trimester, which lasts from months four to six (or weeks 13 to 26), marks further development of the fetus, including massive physical growth. The last is the third trimester which continues from week 27 to week 40. The child's birth marks the end of the third trimester.