Chapter 4 Prenatal Development and Birth • Germinal: The First 14 Days • Implantation occurs about a week after conception, the burrowing of the organism into the lining of the uterus, where it can be nourished and protected during growth. • An estimated 58 percent of all natural conceptions and 75 percent of all in vitro conceptions fail to become property implanted. • How Do Birth Control Pills Work • Embryo: From the Third Through the Eighth Week • During this period the zygote begins to differentiate into three distinct systems. At 22 days after conception these fold become the neural tube. • Fetus: From the Ninth Week Until Birth • During this period the indifferent gonad appear • The age of viability
Risk Reduction • Teratology is the science of risk analysis. Specifically, teratology refers to the causes, mechanisms, and manifestations of abnormal development. • Prenatal development may be disrupted by teratogens (drugs, diseases, chemicals, and radiation), which can attack the developing embryo or fetus and produce serious birth defects. • Critical period. Teratogens are dangerous throughout pregnancy; however, many of these agents are especially troublesome during the first eight weeks, when the major organs and body parts are developing. Many diseases may produce birth defects. Rubella, syphilis, herpes, and toxoplasmosis (from undercooked red meat and cat & cat feces) are particularly harmful. • In prenatal development the time when a particular organ or other body part is most susceptible to teratogenic damage. • There are two critical periods: • at the beginning of the pregnancy and • at the end of the pregnancy.
Specific Teratogens • Rubella is a mild but very contagious disease that is preventable with a vaccine. Other names for rubella are German measles and three-day measles. Rubella is dangerous because of its ability to harm unborn babies. Infection of a pregnant woman can result in miscarriage, stillbirth, or serious birth defects. The most common birth defects are blindness, deafness, heart damage, and mental retardation. • HIV is the virus that causes AIDS. It kills an important kind of blood cell - the CD4 T lymphocyte, or T cell. These T cells are the quarterbacks of the immune system. As they die off, the body becomes more and more vulnerable to other diseases. • AIDS is short for acquired immune deficiency syndrome. AIDS is a disease that slowly destroys the body's immune system.
Some drugs that may post particular problems include- Alcohol; - Amphetamines; - Antibiotics such as Streptomycin, Terramycin and Tetracycline; - Some anticonvulsants such as Dilantin for epilepsy; - Barbiturates, - Hallucinogens such as LSD and marijuana; - Tranquilizers such as Valium; - Narcotics; sex hormones such as those contained in birth control pills and drugs to prevent miscarriages; tobacco; and vitamins (A and D in excessive doses). These are known to cause congenital malformation and complications at birth. In addition, radiation and environmental chemical pollutants such as mercury and lead discharged into the air may have adverse effects on an unborn child.
Low Birthweight • In 2000, infants born to African-American mothers were twice as likely to be low birthweight (less than 2500 grams) and nearly three times as likely to be very low birthweight (less than 1500 grams) as infants born to white mothers. The respective rates of low birthweight and very low birthweight for African-American infants were 13.0 and 3.1 percent, compared to 6.5 and 1.1 percent for white infants. Rates of low and very low birthweight were also higher for Native American (6.8 and 1.2 percent, respectively) and Asian/Pacific Islander infants (7.3 and 1.0 percent, respectively). • Learning disabilities and low academic performance among children born at very low birthweight can persist even into young adulthood, according to a study published today in The New England Journal of Medicine. • "Half of the neurological disabilities in children are related to being born too soon," said Dr. Jennifer L. Howse, president of the March of Dimes. "We've known for some time that being born prematurely or at low birthweight (less than 5-1/2 pounds) can cause serious problems with learning during a child's early school years. Now we see that these disadvantages can last all through high school and beyond. We must learn more about preventing low birthweight and prematurely from occurring in the first place to give every child the best start in life."
Some Disorders Influenced by Heredity and Environment a. Alcoholism • Fetal Alcohol Syndrome (FAS) b. Schizophrenia c. Infantile Autism d. Depression Specific Teratogens • Nutrition and Poverty In 1968, it was estimated that 14 million Americans were going hungry. Nearly thirty years later, the U.S. Department of Agriculture reported that nearly 35 million Americans lived in households experiencing hunger and food insecurity. For school children, missing breakfast diminishes the ability to recall and use newly acquired information, verbal fluency, and control of attention.1 In addition, one study even links reduced rates of suspension with increased breakfast consumption.
Born Too Soon- Breathing problems Babies born before 32 weeks, and especially those weighing under 1,500g (3lb 5oz), usually have immature lungs which cannot secrete surfactant, a foamy substance that prevents the inner surfaces of the lungs from sticking together. This frequently results in severe breathing difficulties, a condition known as Respiratory Distress Syndrome (RDS). After 32 weeks, RDS is far less common.- Premature babies can be very prone to infection because their immune systems are not fully developed.- Premature babies may also suffer from jaundice because their livers are immature; they may be treated with phototherapy lamps, similar to ultraviolet light sun beds.
Small for Gestational AgeSmall for gestational age (SGA) is a term used to describe a baby who is smaller than the usual amount for the number of weeks of pregnancy. SGA babies usually have birth weights below the 10th percentile for babies of the same gestational age. This means that they are smaller than 90 percent of all other babies of the same gestational age. SGA babies may appear physically and neurologically mature but are smaller than other babies of the same gestational age. SGA babies may proportionately small (equally small all over) or they may be of normal length and size but have lower weight and body mass. SGA babies may be premature (born before 37 weeks of pregnancy), full term (37 to 41 weeks), or post term (after 42 weeks of pregnancy).
Some factors that may contribute to SGA include the following: Maternal factors: • high blood pressure • chronic kidney disease • advanced diabetes • heart or respiratory disease • malnutrition, anemia • infection • substance use (alcohol, drugs) • cigarette smoking
Factors involving the uterus and placenta: • decreased blood flow in the uterus and placenta • placental abruption (placenta detaches from the uterus) • placenta previa (placenta attaches low in the uterus) • infection in the tissues around the fetus Why is SGA a concern? When the fetus does not receive enough oxygen or nutrients during pregnancy, overall body and organs growth is limited, and tissue and organ cells may not grow as large or as numerous. Some of the conditions that cause SGA and IUGR restrict blood flow through the placenta. This can cause the fetus to receive less oxygen than normal, increasing the risks for the baby during pregnancy, delivery, and afterwards.
The Normal Birth • Signs of the start of labor are: - painful contractions with a certain regularity - effacement and/or dilatation of the cervix - leakage of amniotic fluid - bloody discharge • The beginning of the second stage is marked by the following symptoms: • the woman feels the urge to bear down, because the amniotic sac or the presenting part protrudes through the dilated cervix and presses against the rectum; • often the membranes rupture spontaneously; • usually there is full dilatation of the cervix, but sometimes the woman feels the urge to push at an earlier stage of dilatation. If a rim of cervix is left it will be pushed aside by the presenting part.
Normal Birth THE THIRD STAGE OF LABOUR • In this stage of labor placental separation and expulsion take place; for the mother the main risks are hemorrhage during or after separation of the placenta, and retention of the placenta. Postpartum hemorrhage is one of the main causes of maternal mortality; the large majority of these cases occur in developing countries (Kwast 1991). Birth Complications • Cerebral Palsy • Anoxia The Beginning of Bonding
The Newborn's First Minutes • Apgar Scale • Medical Attention • Episiotomy • Cesarean section • Most births in the USA occur in a medical facility. Birth Complications • Cerebral palsyis a term that describes a group of disorders that affect movement control. There is not one specific cause of cerebral palsy, however, it can be caused by injury to the brain before, during, or after birth. • Anoxia is a term is used to describe a deficiency in, or blockage of, the supply of oxygen in the body. Although not common, anoxia may occur during any stage of fetal development, infancy, or throughout life
Parent-newborn bond-the strong feelings of attachment that arise between parents and their newborn infants. • Social Construction Theory suggests that we learn from and among persons in social interaction and the main vehicles which convey this meaning: symbols, including language, cultural myths. Together, they influence and form our understanding of reality • Postpartum depression.Many women feel sad or "blue" shortly after their babies are born. These "postpartum blues" last about 3 to 7 days, are relatively mild, go away without treatment, and are considered to be a normal part of childbirth. In 10% to 15% of postpartum mothers, feelings of sadness, disinterest, and anxiety continue for 2 or more weeks.