Chapter 4: Zygote to Newborn Dr. M. Davis-Brantley

Germinal Period: The First 14 days Referred to as the first 2 weeks of development after conception Ovum>Egg travels the Fallopian tube>Sperm fertilizes egg>fertilized egg is later implanted in the uterus During these first days while the fertilized egg travels the fallopian tube there is rapid duplication and multiplication By the eight-celled stage, differentiation occurs –Meaning early “stem” cells take on distinct characteristics and gravitate toward particular locations (the areas they will later become) The outer cells are to become the placenta their task is to achieve implantation –60% (natural conceptions) & 70% (in vitro conceptions) fail to implant Video—The 1 st MonthVideo—The 1 st Month First 14 Days

Embryo: 3 rd week through 8 th week Video about the Embryonic Period Video—The Embryo Takes Shape Characterized by the cells becoming a distinct being –4 th week: (1/8 inch) head, ears, eyes, nose, mouth blood vessel which will become the heart Cardiovascular system begins to show activity –5 th week: Embryo has grown twice in size Buds that will become arms and legs appear and tail-like appendage extends to form a spine

Fetus: 9 th week until Birth 3 rd month: sex organs begin to take shape End of 3 rd month: – the fetus has all its body parts –Weighs ~3 oz., and is ~3 inches Video--Fetal Stage Video—Feeding the Growing Fetus

Fetus: 9 th week until Birth 2 nd Trimester –Heartbeat becomes stronger –Digestive system develops –Excretory system develops –Fingernails, toenails, and buds for teeth form –Hair grows Brain: significant growth (grown 6 times in size) Undergoing significant neurogenesis (develop new neurons) Undergoing significant synaptogenesis (connections b/n neurons) Age of Viability –The age (22 weeks) at which the fetus can survive outside of the mother’s uterus with specialized care –Based on fetal brain functioning since the brain regulates the basic body functions

Fetus: 9 th week until Birth 3 rd trimester –Odds of survival outside of the womb increase significantly each day –There is maturation of the respiratory and cardiovascular systems Lungs begin to expand and contract –Body weight increases rapidly to ensure that the developing brain is well nourished This decreases defects and difficulties in learning in the future –Video—3 rd TrimesterVideo—3 rd Trimester

Risk Reduction Teratogens are agents and conditions that can impair prenatal development and lead to birth defects or even death –Teratogens can include viruses, drugs, chemicals, stressors, and malnutrition Behavioral Teratogens are teratogens that can harm the prenatal brain which results in the child having difficulty with learning, hyperactivity, and antisocial behavior

Risk Reduction Some teratogens cause damage only during specific prenatal periods Critical Period refers to the time when a particular organ or body part is most susceptible to teratogenic damage This is why obstetricians recommend couples get counseling, take multivitamins, stop taking medications before pregnancy

Risk Reduction Threshold effect—Some teratogens are virtually harmless until exposure reaches a certain level –Ex: Prenatal vitamins in excess can cause fetal abnormalities Interaction effect—Condition whereby the risk of a teratogen causing harm increases when one substance intensifies the effects of another teratogen –Ex: Alcohol, tobacco, and marijuana

Risk Reduction Genes can determine whether a specific teratogen will be harmful –Ex: degree of FAS, birth disorders such as cleft lip, cleft palate, and clubbing –Ex: Genes are implicated in the teratogenic effect that results in spina bifida

Specific/Preventable Teratogens HIV as a teratogen –Mothers transmit the virus during pregnancy and through breast feeding –Can prevent transmission by Taking antiretroviral drugs beginning 14 weeks Give birth by cesarean section Does not breast feed Fetal Alcohol Syndrome (FAS) –A cluster of birth defects caused by mother consuming alcohol during pregnancy Defects include abnormal facial features, slowed physical growth, slowed mental development –Damage increases when alcohol is combined with other psychoactive drugs (cigs, cocaine, meth, LSD, psychotropic medications, etc…)

Small Babies Low birth babies –A birthweight of less than 5 ½ pounds –Due to the fetus growing too slowly Preterm birth –Birth that occurs 3 or more weeks before full term, that is 35 or less weeks Small for gestational age –Birthweight significantly lower than expected –Typically a sign of serious problems –Psychoactive substance use, malnutrition

The Birth Process During the final month, fetus typically changes position to prepare for birth proces –Short VIDEO and Extended VIDEOVIDEOExtended VIDEO Babies that are breech are positioned so that buttocks, feet, or knees first (1 in 20 babies are breech) At 266 th day after conception, the fetal brain sends a message to release certain hormones that pass through the mother’s bloodstream This hormone triggers uterine muscles to contract and relax, which begins active labor Babies are born, on average, after 8 hours of active labor and 3 hours for subsequent births

Newborn’s First Minutes Babies typically begin to breathe on their own and take first breaths with spontaneous cries Oxygen is entering for the first time and changes the babies skin color because of circulation Eyes open wide, Finger began to grab, toes stretch and retract Those attending to the child must remove mucus from the throat, umbilical cord must be cut to detach the placenta, baby is wrapped to preserve body heat

Newborn’s First Minutes Apgar Scale is a means of quickly assessing a newborn’s body functioning The following is checked at birth and again 5 minutes after birth: –Baby’s color –Heart rate –Reflexes –Muscle tone –Respiratory Effort A total score of 7 or higher indicates no danger

Variations in Births Cesarean section is a surgical childbirth where there is an incision through the mother’s abdomen and uterus to allow the fetus to be removed quickly –Fewest Cesarean Sections occur in Ghana, Kenya –Most take place in Mexico and Brazil

Birth Complications Cerebral Palsy –A disorder that results from damage to the brain’s motor centers. People with cerebral palsy have difficulty with muscle control, which can affect speech or other body movements –Believed to be caused by excessive pain medication, slow breech birth, forceps but now discovered it often results from genetic vulnerability and maybe worsened by teratogens Anoxia –A temporary lack of oxygen that can cause brain damage or death

After Birth and Bonding Parental Alliance –Cooperation b/n the mother and father because of their mutual commitment to their children. –In a parental alliance, both parents agree to support each other in their shared parental roles Postpartum Depression –A mother’s feelings of sadness, inadequacy, and hopelessness in the days/weeks after giving birth –Feelings are partly due to physiological (especially hormonal) and partly cultural, especially if the woman does not receive adequate assistance and encouragement from the father and helpers Parent-Infant Bond –A strong loving connection that forms as parents hold, examine, and feed their newborn