Fetal development is the progressive development that occurs between the fertilization of an egg to the birth of a baby sometimes illustrated in general periods of trimester. The first trimester is the initial 12 weeks; second trimester weeks begin from week 13 through week 27; and third trimester begins from week 28 to week 40. The first trimester is an important time of development when all the organ systems of the body are shaping and becoming functional. Cells in the embryo travel to major developmental positions, forming the human being as it takes on a human appearance. On the contrary, the second and third trimesters are phases of growth and enhancement of the organ system.
During the first trimester, during the 1st to the 12th week, nearly all the embryo’s physiological systems and body parts start to form. During the 1st day, fertilization takes places, as all human chromosomes are present; distinctive human life commences. From the 1st to the 5th day, the embryo starts an implantation in the uterus; it is about 0.6 centimeter long. By this time, three cell layers have formed: the ectoderm (outer layer), from which sense organs, nervous system, and the skin will grow; the mesoderm (middle layer), from which the excretory, circulatory, and muscular systems will form; and the endoderm (inner layer), from which the lungs, glandular systems and digestive system will develop. During the 22nd day, the heart starts to beat with the child’s blood type different from the mothers. In the 3rd week, the child’s nervous system and backbone spinal column form. During this period, the embryo’s intestines, kidneys and liver, start to take shape. By the close of the 4th week, the child is ten thousand times bigger than the fertilized egg.
During the 5th week, hands, legs, and eyes start to develop. In the 6th week, brain waves are evident; lips and mouth are observable; fingernails start to form. During the 7th week, toes, eyelids and nose take their shape. The baby begins to swim and kick. Within the 8th week, every organ is positioned, bones start to substitute cartilage, and fingerprints start to form. In addition, during the 2nd month the umbilical cord build ups and attaches the embryo to the placenta. By the 8th week the baby can start to hear. This all takes place within the first 2 months of pregnancy, which is referred to as embryonic stage. Throughout the 9th and the 10th week, teeth start to form and the fingernails grow. The baby can turn his head, hiccup and frown. During the 10th and 11th week, the baby can inhale amniotic fluid and urinate. In the 11th week, all organ systems are operational. The embryo has a digestive and a central nervous system along with a skeletal structure. The final week of first trimester, 12th week; the fetus has all parts required to experience pain, counting thalamus, nerves and spinal cord. Vocal cords are whole and the fetus can suck its thumb (Scott & Fong, 2009, p. 425).
The Second Trimester
During the 15th week, the baby has an adult's taste buds. During the 4th month, the first month of the second trimester, the utmost amount of fetal growth occurs. Bone marrow starts to form and the heart pumps 25 quarts of blood daily. By the end of the 4th month, the baby grows by 8 to10 inches long and weighs equal to half a pound, the lower body is progressively more larger and the head is now 1/3 the length of the body. The fetus can move, this movement is referred to as quickening, and is sensed by the mother. In the 17th week, the fetus may experience dream (REM) sleep. During the 20th week, the fetus identifies its' mothers voice. In the 5th month which is the central point of the pregnancy, the fetus weighs about 1 pound and is almost 12 inches long.
It sleeps and wakes and has a preferred body position. Within the 5th and the 6th month, the fetus tries to breath by inhaling amniotic fluid into its growing lungs. The fetus will take hold at the umbilical cord when it senses it. The fetus is now twelve inches long or more, and weighs up to one and a half pounds. During the 6th month, the fetus grows to about 2 inches long and adds another pound. The fetus is currently twelve inches long or more, and weighs equal to one and a half pounds. By this period, the fetus’s eyes are shaped and sensitive to light. Moreover, the fetus can hear uterine sounds. The skin is wrinkled and covered with fine hair. By the end of this trimester, modification of body features have transpired, movement is stronger, and additional growth has been attained (Scott and Fong, 2009, p. 425).
The Third Trimester
During the period of the third trimester, the baby poses itself more or less for birth. As a fat layer is laid beneath the skin, the fetus retains a baby like form. During the 7th to the 9th month, the baby uses four of the five senses, namely, sight, touch, taste and sound. Antibodies are developed and the baby's heart starts to pump 300 gallons of blood daily. By the end of the 8 month, the fetus weighs approximately 5 pounds and 4 ounces and is about 20 inches long. During the 8th and the 9th month, skin redness decreases and wrinkles start to vanish as the fetus starts to gain about 11/2 pound a week.
The nails reach the end of the fingers and toes and the fetus movements become limited because of its firm fit in the uterus. As birth becomes forthcoming, in the 38th to 40th week, the head is 60 per cent of its complete size, the fine body hair has vanished, and the skin becomes smoother and is now enclosed with a waxy protective substance called the vernix caseosa. During this last trimester, the fetus attains a weight and size that prepare it to live separately from the mother. Roughly 1 week before the birth the fetus discontinues growing, and the most common fetal position now is head down into the pelvic cavity. The baby is prepared for delivery and birth (Scott and Fong, 2009, p. 425).
Morning sickness, also referred to as nausea gravidarum, pregnancy sickness or nausea and vomiting of pregnancy (NVP), is a pregnancy symptom that affects approximately 50 and 80 percent of the pregnant women. It occurs mainly in the first trimester, when the fetus is most vulnerable to toxins, micro-organisms and parasites. Nausea and vomiting can be one of the foremost signs of pregnancy and generally starts around the 6th week of pregnancy and ends around the 12th week of pregnancy. It occurs at any time of the day but worsens in the morning since there is no food in the stomach.
Morning Sickness as a Defense Mechanism
Morning sickness is believed to be a trait that decreases ingestion of noxious agents, for instance toxins and pathogens, and thus protects the developing embryo and the expectant mother. Such noxious agents are inclined to be hazardous or indicators of hazardous substances within the food. Nausea occurs when a pregnant woman reacts to the smell or taste of secondary compounds that may as a result cause the evasion of avoidance or regurgitation of microbial and toxin-laden contaminated foods.
Fetal harm during the first trimester of pregnancy could have marked consequence, such as causing damage to minute number of cells during the fetus early development. This may result to considerable damage to organs or tissues that build up from those cells, causing miscarriages or birth defects. Heightened nausea in reaction to secondary chemicals in food may protect developing embryo and fetus from such harm. This hypothesis is supported by the timing of symptoms during pregnancy and decreased risks of miscarriage among women experiencing morning sickness.
This hypothesis speculates that morning sickness acts as a defense mechanism by helping pregnant women to avoid consumption of certain substances including coffee, tobacco, and alcohol that could be detrimental to the developing fetus. Moreover, during this period, pregnant women have a high dislike of fish, poultry, and eggs, as well as fatty and fried foods. They also tend to prefer bland foods and dislike spicy and pungent foods, which have a high quantity of toxic compounds. In light of this, scientists have found that animal products could be risky to an expectant mother and the embryo, possibly because these products have pesticides, parasites, and other disease-causing organisms.
The dislike during pregnancy for animal-originated food is believed to have protected pregnant women and their unborn babies for hundreds of generations. Hence, the pregnant mother has hormonally triggered mechanisms that influence her food choices with the intention of protecting the young fetus from toxins, and these mechanisms are active during the time the fetus is most at risk. These feeding and sickness mechanisms are stopped throughout the second and third trimester when the nutritional requirements of the fetus become bigger and the mother requires nutrients to maintain them both. Morning sickness is also attributed to the increase of progesterone and estrogen which irritate the stomach lining. Hence, morning sickness has permitted more fetuses to crossover healthily until delivery and birth.
A congenital disorder is a birth defect and disease that begins at conception or in the early phase of pregnancy. Congenital disorders differ widely in symptoms and abnormalities. The global incidence of congenital disorders is estimated have contributed to a high rate infant deaths in U.S. and around the globe. Congenital disorders account to a large percentage of the health problems observed in infants and children (Ebnezar & Johari, 2010, p. 487).
Congenital disorders may possibly be caused by genetic or environmental factors. Majority of the causes are unknown or may be caused by the multifaceted interaction between genetic, non-genetic and environmental factors, identified as multifactorial. Other congenital defects may be caused by recognized environmental exposures for instance, intake of drugs, viruses, environmental pollution, maternal addiction with tobacco, alcohol or smoking, x-ray exposure during pregnancy, anomalous intrauterine environment , and maternal diseases for example diabetes. Moreover, some congenital disorders are inherited through the genes in the ovum or sperm. The disorder may be connected to chromosomal abnormalities, single gene disorders or polygenic inheritance.
Gestational and acquired congenital disorders of the newborn are present at birth and are caused by prenatal and perinatal harm as a result of birth trauma, maternal infection, maternal disorders or disease, substance use, or abnormalities related to pregnancy. Roughly 2 percent of all newborns born have a major malfunction. These disorders affect the skeletal, central nervous, cardiovascular, genitourinary and gastrointestinal systems. Defects such as cleft lip, cleft palate and severe neural tube defects are apparent at birth, but others may be realized only after a full physical examination.
Congenital disorders, which report for more than 20 percent of infant deaths, are preventable in many occurrences. Some disorders, for example, hemophilia, Down syndrome and Tay-Sachs disease have a recognized genetic basis and can be prevented by prenatal diagnosis and/or genetic screening. Prevention of congenital disorders must be attained by particular attention to environmental factors rather than by endeavoring to improve heredity.