7. 9th week to birth embryology

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Information about 7. 9th week to birth embryology

Published on January 22, 2014

Author: revathithie

Source: slideshare.net

Sex Chromosomes • • • • • • XX = Female XY = Male XO = Female, Turner’s Syndrome XXY = Male, Kleinfelter’s Syndrome XYY = Male, Double Y Syndrome Fragile X = Male or Female Berch & Bender (1987); Berger, K. S. (2006); Doyle & Paludi (1998). 1

Part I Chapter Four Prenatal Development and Birth From Zygote to Newborn Risk Reduction Birth 2

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) 3

Timing • Pregnancy begins at conception – Start of gestational age – Obstetrician may use LMP – 14 days before conception • Length of pregnancy – 266 days, 38 weeks, or 9 months – LMP = 40 weeks 4

Timing • Trimesters (3 mo.) vs. germinal, embryonic, and fetal periods • Due date – Based on LMP – 5% babies born on that date – Full term = 3 weeks early or 2 weeks late (preterm and post-term) 5

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 6

• 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 7

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 8

Embryo: From the Third Through the Eighth Week • Embryo: a developing human organism from about the third through the eighth week after conception 4 weeks ¼ in. 5 weeks 7 wks. <1 in. 8 wks. 1 in. 9

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 10

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 11

• In the fourth, fifth and sixth months: – Heartbeat becomes stronger – Cardiovascular system becomes more active – Brain increases about six times in size 12

• 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 13

Final 3 Months • 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 14


Risk Reduction • Teratogens: agents and conditions that can – Harm the prenatal brain – Impair the future child’s intellectual and emotional functioning 16

Determining Risk • Once it was thought the placenta screened out all harmful substances. 17

– 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 18

Timing of Exposure 19

– Threshold effect: situation in which a certain teratogen is relatively harmless in small doses but harmful once exposure reaches certain level (the threshold) • Vitamin A beneficial in low doses, dangerous in high doses – Interaction effect: result of a combination of teratogens • Alcohol, tobacco, and marijuana 20

Genetic Vulnerability – 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 – Neural tube defects 21

Protective Measures • 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 though the woman avoids all known tetragons while pregnant 22

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 23

• Fetal alcohol syndrome (FAS) : cluster of birth defects – – – – Abnormal facial characteristics Slow physical growth Cognitive delays or deficits Impulsiveness • Fetal alcohol effects (FAE) : condition in which child has been exposed to alcohol before birth – Some signs of fetal alcohol syndrome but does not meet all the criteria 24

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) 25

• For full-term fetus and a healthy mother, birth can be simple and quick 26

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 27

Apgar scale: quick assessment of newborn’s condition including: – – – – – the baby’s color heart rate reflexes muscle tone respiratory effort 28

Medical Intervention • About 31% of births in the U.S. are cesarean section, (also called c-section) 29

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 30

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. 31

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. 32

• Preterm birth: 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 33

Social Support • 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 34

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. 35

• 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 36

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 37

• 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 38

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 39

Bonding • Parent-infant bond: strong, loving connection that forms as parents hold, examine, and feed newborn 40

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