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Part I. Chapter Four. Prenatal Development and Birth. From Zygote to Newborn Risk Reduction Birth. From Zygote to Newborn. Prenatal development is divided into three main periods: germinal period (0-2 weeks) embryonic period (3-8 weeks) fetal period (9 weeks-birth).
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Part I Chapter Four Prenatal Development and Birth • From Zygote to Newborn • Risk Reduction • Birth
From Zygote to Newborn • Prenatal development is divided into three main periods: • germinal period (0-2 weeks) • embryonic period (3-8 weeks) • fetal period (9 weeks-birth)
Germinal: The First 14 Days • germinal period: • first two weeks of prenatal development after conception • Characterized by rapid cell division and the beginning of cell differentiation.
embryonic period: • approximately the third through eighth week after conception • all body structures, including internal organs, begin to develop • fetal period: • stage of prenatal development from ninth week after conception until birth, during which the organs grow in size and mature in functioning
Germinal: The First 14 Days • implantation: • process in which developing organism burrows into placenta that lines uterus • placenta: • organ that surrounds developing embryo and fetus, sustaining life via the umbilical cord
Embryo: From the Third Through the Eighth Week • Embryo: • name for a developing human organism from about the third through the eighth week after conception
Fetus: From the Ninth Week Until Birth • The developing organism is called a fetus from the start of the ninth week after conception until birth. • during the fetal period the fetus develops from tiny, sexless creature to a 7 1/2-pound, 20-inch boy or girl
The Third Month • At the end of the third month, the fetus has all its body parts. • Weighs approximately 3 ounces, and is about 3 inches long. • Early prenatal growth is very rapid, but there is considerable variation from fetus to fetus, especially in body weight.
In the fourth, fifth and sixth months: • heartbeat becomes stronger • cardiovascular system becomes more active • brain increases about six times in size
age of viability: • Age at which a fetus can survive outside the mother’s uterus if specialized medical care is available. • about 22 weeks after conception • In the final three months of prenatal life: • brain waves indicate responsiveness. • lungs expand and contract, using the amniotic fluid as a substitute for air. • heart valves, arteries, and veins circulate the fetal blood.
Risk Reduction • teratogens: agents and conditions that can: • harm the prenatal brain • impairing the future child’s intellectual and emotional functioning
Determining Risk • Once it was thought the placenta screened out all harmful substances. • Doctors on an Australian military base traced an increase in blindness among newborns to rubella (German measles) contracted by pregnant women a few months earlier. • Realized that some diseases during pregnancy could harm a fetus.
The effort to understand what triggered such damage gave rise to: • teratology: science of risk analysis, the study of birth defects • risk analysis: to determine likelihood of harm, science of weighing the potential effects of a particular: • event • substance • experience
Second important factor is the dose and/or frequency of exposure. • threshold effect: situation in which a certain teratogen is relatively harmless in small doses but harmful once exposure reaches certain level (the threshold) • interaction effect: result of a combination of teratogens • Sometimes risk is greatly magnified when embryo or fetus is exposed to more than one teratogen at the same time.
Several lines of evidence suggest that genes may be crucial. • Dizygotic twins, exposed to same teratogens but have only half their genes in common, are born with different abnormalities. • Suggests both protective and vulnerable genes. • Cleft lip, cleft palate, club foot more common in some families. • Suggests genetic vulnerability. Genetic Vulnerability
Impact of teratogens cannot be predicted before mid-pregnancy. • Some pregnant women are exposed to the tetragons with no evident harm. • Some defects occur even thought the woman avoids all known tetragons while pregnant. Protective Measures
A View From Science • Alcohol in high doses is a proven teratogen. • 40 years ago drinking during pregnancy was believed to be harmless. • Obstetricians noted that some patients who drank heavily while they were pregnant had babies with distorted faces. • fetal alcohol syndrome (FAS) • fetal alcohol effects (FAE)
fetal alcohol syndrome (FAS): cluster of birth defects, including: • abnormal facial characteristics • slow physical growth • retarded mental development • fetal alcohol effects (FAE): condition in which child has been exposed to alcohol before birth • has some signs of fetal alcohol syndrome but does not meet all the criteria
Benefits of Prenatal Care • Tests done during pregnancy can diagnose problems early on, and remedies can be put in place in some instances. • sonogram: image of unborn fetus (or an internal organ) produced by high-frequency sound waves (ultrasound)
For full-term fetus and a healthy mother, birth can be simple and quick.
The Newborn’s First Minutes • Most newborns begin to breathe as soon as their head emerges. • first breath causes infant’s color to change • eyes open wide • the tiny fingers grab • toes stretch and retract • mucus in the baby’s throat is removed • umbilical cord is cut to detach the placenta • placenta is expelled
Apgar scale: quick assessment of newborn’s condition including: • the baby’s color • heart rate • reflexes • muscle tone • respiratory effort
Medical Intervention • about 31% of births in the U.S. are cesarean section, (also called c-section) • incision through mother’s abdomen and uterus to allow fetus to be removed quickly, instead of being delivered through the vagina
Birth In Developing Nations • In the U.S. only 1% of births take place at home. • Worldwide most births occur at home. • doula- a woman who helps with the birth process - also helps with breastfeeding and newborn care.
Anoxia • anoxia: • lack of oxygen that can cause brain damage or death to the baby • means “no oxygen” • cerebral palsy: • disorder that results from damage to brain’s motor centers • People with cerebral palsy have difficulty with muscle control, so their speech and body movements are impaired.
Low Birthweight (LBW) • Average weight of a newborn is 7½ lbs. • low birthweight (LBW): a body weight at birth of less than 5½ lbs. • very low birthweight (VLBW): a body weight at birth of less than 3 lbs, 5oz. • extremely low birthweight (ELBW): a body weight at birth of less than 2 lbs, 3 oz.
pretermbirth: occurs 3 or more weeks before full 38 weeks of a typical pregnancy • Preterm babies are typically (but not always) LBW because they miss final weeks of weight gain. • small for dates or small for gestational age (SGA)- birth weight is lower than expected given the time of conception.
The developing person is affected by quality of: • medical care • education • culture • social support • Fathers and other relatives, neighbors, cultures, and, clinics can reduce risk of birth complications Social Support
Mothers, Fathers, and a Good Start • Birth complications can have a lingering impact on the new family, depending partly on: • sensitivity of hospital care • the home • To reduce stress on an infant who has to stay in the hospital, parents are encouraged to help with early caregiving.
kangaroo care: form of child care in which the mother of a low-birthweight infant spends at least an hour a day holding the baby between her breast, like a kangaroo
Help from Fathers • Fathers can be crucial in the effort to produce a healthy baby. • Supportive father-to-be helps a mother-to-be: • stay healthy • well nourished • drug-free
parental alliance: cooperation between a mother and a father based on mutual commitment to their children • Parents agree to support each other in their shared parental roles.
Postpartum Depression • new mother’s feelings of inadequacy and sadness in days and weeks after giving birth including: • irritability • eating disruptions • sadness • feeling overwhelmed and inadequate • affects 10-15% of women
Bonding • parent-infant bond: strong, loving connection that forms as parents hold, examine, and feed newborn • cross-fostering: newborns are removed from their biological mothers in first days of life and raised by another female or even male