Pregnancy occurs when an egg is fertilized by a sperm, and the egg grows inside a woman’s uterus also called a woman’s womb, and will develop into a baby. In humans, this process takes about 264 days, but the obstetrician will date from the last menstrual period or 280 days which is 40 weeks. There are a number of things that must fall into place in the right order to become pregnant and have a baby. The creation of a human being requires the right environment, the right timing, the right factors, and a great deal of luck.
The term intra-uterine pregnancy is used to describe when a fertilized egg is implanted in the uterus and an embryo grows. The length of time of a pregnancy is divided into three sections called trimesters or stages, which is about three months each. Each trimester has particular events and developmental markers. The first trimester or builds the foundation of the different organ systems. The first trimester or stage is the germinal period or the zygotic period. It is the first two weeks of prenatal development. Near the end of the two weeks the single-celled a zygot, developes into a cluster of cells called the embryo.
The second stage or trimester is called the embryonic period, which is week three through week eight. In the first month the embryo is usually 1/8th of an inch or . 275 cm long. I weighs about 3 grams. A yolk sac has already formed at this stage. Organs and major systems within the body of the embryo forms during this period. The embryo’s lifeline is the umbilical cord, which provide the embryo nourishment, oxygen, and water from the mother. The umbilical cord also carries away waste. The placenta is also developed, protecting the embryo, by keeping the mother’s blood from mingling with the developing embryo.
It also protects the embryo by preventing harmful substances in the mother’s blood from reaching the embryo, such as teratogens. Teratogens are harmful substances that can cause birth defects. By three weeks the baby’s brain cells have started to form, creating a sheet of neural cells that curls and forms a neural tube lined with stem cells. At the top of the neural tube forms a bulge which later consists of the hind brain, mid brain, and fore brain. When the neural tube expands, it creates ventricals and the core of the brain.
Ventricals that are filled with ceobraspinal fluid cushions the brain and also provides nutrients to the brain and spinal cord. In the second month, It is about an inch or 2. 5 cm long. It is 8. 7 grams heavy. The head, tail and the umbilical cord are formed and the sex glands are determined. The limbs, toes, fingers, the skeleton and bone cells have also been formed at this stage. A distinctively human appearance develops. Facial features, the main organ systems also take shape. By the end of the eighth week, the structures of the brain, heart, liver, limbs, ears, nose and eyes evolve.
This is a most critical period of development. Harmful medications, drugs and alcohol may disturb the processes of development and cause defects or snags in the embryo. The fetal period or trimester is the third month to actual birth of the baby. At this stage the baby is called the fetus with distinctively human features. At the end of the third month the baby can move its arms, legs, mouth and head, although at this moment of time, the movements are uncoordinated and cannot be felt by the mother. The fetus is now one to three inches long and weighs roughly an ounce. The baby can also start using reflexive responses .
During the fourth month the mother can feel quickening, which is the baby moving inside the uterus. At five months all brain cells of the baby for birth are developed. During this period the baby has sleep and wake cycles. In the sixth month the fetus’s brain activity is similar to that of a newborn baby. The final two months the fetus usually doubles in weight. The fetus will usually add on about three to four pounds of body fat. This additional body fat will help the newborn baby adjust to different temperatures outside the womb. The closer to birth, the fetus’s growth slows and the actions of the body systems become more regular.
At about forty weeks or 280 days, the fetus is ready to emerge in the world. At birth a baby’s brain is only one forth the size of an adult’s brain. The brain will weight at birth less than a pound. After a baby is born the neurons grow in size and continue to develop. A newborn enters the world with a array of physical and sensory capabilities. In the beginning right at birth a baby’s behavior is mostly reflex moves that are to enable his survival in the new world. In conclusion, a baby is a very precious and wonder gift that some women are blessed with. It is very mportant for a new expectant mother to understand the stages of pregnancy. A new mother should research and read all that she can read to gain knowledge of what is going to happen in the months to come. The more knowledge a new mother has is very beneficial for her well being and also to interact with her physician about symptoms and problems if any arise.