Chapter 4: Prenatal Development and Birth McGraw-Hill © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.

Prenatal Development

Prenatal development is divided into 3 periods and lasts approximately 266 days Germinal period: first 2 weeks after conception, zygote created (see Fig. 4.1) Embryonic period: occurs from 2 to 8 weeks after conception (see Fig. 4.2) Fetal period: begins 2 months after conception and lasts until birth

The Three Trimesters of Prenatal Development Conception to 4 wks To 8 weeks To 12 weeks To 16 weeks To 20 wks To 24 wks To 28 wks To 32 wks 36 to 38 weeks Less than 1/10th of an inch long Less than 1 inch long About 16.5–18 inches long, weighs 4 to 5 pounds 19 inches long, weighs 6 pounds About 5.5 inches long, weighs about 4 ounces About 10-12 inches long, weighs 1/2 to 1 pound About 11-14 inches long, weighs 1 to 1.5 pounds About 14-17 inches long, weighs 2.5 to 3 pounds About 3 inches long, weighs about 1 ounce First trimester begins Third trimester begins The Three Trimesters of Prenatal Development See Figure 4.3 in textbook for more details Fig. 4.3 Second trimester begins

Teratogen: any agent that causes birth defects Drugs (prescription, nonprescription) Alcohol, tobacco Environmental pollutants Infectious diseases Nutritional deficiencies Maternal stress Advanced age of a parent Severity of damage to the unborn depends on Dose Time of exposure Genetic susceptibility

Teratogens and Timing of Their Effects on Prenatal Development Zygote Embryonic period (wks) Fetal Period (wks) 1 2 3 4 5 6 7 8 9 16 32 38 Central nervous system Most serious damage from teratogens in first 2-8 wks Heart Arms Eyes Legs Ears Teeth Palate Period of susceptibility to structural defects External genitalia Period of susceptibility to functional defects Fig. 4.4

Fetal alcohol syndrome: abnormalities in newborn due to mother’s heavy use of alcohol in pregnancy Abnormalities include: Facial deformities Defective limbs, face, heart Most are below-average intelligence Some are mentally retarded

Moderate drinkers during pregnancy had babies who were less attentive and alert even at 4 years of age Maternal smoking can cause respiratory problems SIDS ADHD low birth weight

Illegal drugs that harm during pregnancy: Cocaine Marijuana Heroin Incompatible blood types (Rh factor) Environmental hazards: exposure to radiation or chemicals STDs, HIV infection, AIDS Other maternal and paternal factors

Percentage of U.S. Women Using Timely Prenatal Care: 1990 to 2001 100 1990 90 2001 80 70 60 50 Percentage 40 30 20 10 Non-Latino White women African American women Latino women Fig. 4.6

Birth

Three stages of birth: Uterine contractions begin at 15 to 20 minutes apart and last 1 minute; this stage lasts an average of 12 to 24 hours Baby’s head begins to move through dilated cervix opening; this stage lasts 1.5 hour on average Afterbirth: umbilical cord, placenta, and other membranes are detached and expelled

Birth complications include anoxia: insufficient oxygen to brain when delivery lasts too long Birth and delivery methods: Hospital delivery room Home delivery with midwife Lamaze method Comparing birthweights in the United States and other countries

Low Birthweight Rates by Country Percentage of low-birthweight infants Luxemburg Low Birthweight Rates by Country Sweden Canada China Czech Republic Switzerland Italy Cuba Kazakstan United Kingdom United States Mexico Ethiopia Nicaragua Turkey Philippines Nepal Pakistan Sierra Leone Haiti Bangladesh 5 10 15 20 25 30 Percentage of low-birthweight infants Fig. 4.7

Causes of low birthweight: Preterm babies Small-for-date babies Problems in developing countries Possible consequences of low birthweight: Brain injuries Lung and liver diseases Learning disabilities ADHD Lower levels in reading and math achievement Deficits are evident in adulthood

Full-term normal weight Comparison of Overall Cognitive Processing Skills of Middle School Students Who Were Born with Low Birthweight or Normal Birthweight 20 30 40 50 60 70 80 90 100 10 Overall cognitive skills score <750 g 750-1,499 g Full-term normal weight Fig. 4.8

About 50% of low-birthweight children are enrolled in special education programs Low birthweight is linked to asthma Some defects can be improved with Early speech therapy Intensive enrichment programs Kangaroo care and massage therapy

Weight Gain Comparison of Premature Infants Who Were Massaged with Those Not Massaged 3 lb. 7 oz 3 lb. 5 oz Premature infants who were not massaged 3 lb. 3 oz 3 lb. 1 oz Infant weight 2 lb. 15 oz 2 4 6 8 10 12 14 Age (days) Fig. 4.9

Measuring neonatal health and responsiveness: Apgar Scale, used 1–5 minutes after birth: evaluate heart rate, body color, muscle tone, respiratory effort, and reflex irritability Brazelton Neonatal Behavioral Assessment Scale performed within 24–36 hours after birth 27 items are organized into 4 categories – physiological, motoric, state, and interaction Assesses newborn’s neurological development, reflexes, and reactions to people

The Apgar Scale 1 2 Score Body Color Blue, pale 1 2 Body Color Blue, pale Body pink, extremities blue Entire body pink Heartbeat Absent Slow – less than 100 beats per min. Fast – 100 to 140 beats per min. Reflex Irritability No response Grimace Coughing, sneezing, crying Muscle Tone Limp and flaccid Inactive, weak, some flexion of extremities Strong, active motion Respiratory Effort Breathing for no more than 1 min. Irregular and slow Breathing good with normal crying Fig. 4.10

The Postpartum Period

Postpartum period lasts about 6 weeks after childbirth when woman adjusts physically and psychologically back to the prepregnant state Influenced by preceding conditions and experiences Mother learns to care for the baby, feel good about herself and those close to her Physical: hormone changes, weight loss, return to menstruation, loss of energy or fatigue Psychological: feelings of depression, anxiety, coping in new role, excessive worrying

Percentage of U.S. Women Who Experience Postpartum Blues and Postpartum Depression Postpartum blues: symptoms appear 2 to 3 days after delivery and subside within 2 to 3 weeks 10% 70% 20% No symptoms Postpartum depression: symptoms linger for weeks or months and interfere with daily functioning Fig. 4.11

Bonding (formation of emotional attachment) between infant and mother: Usually occurs in period shortly after birth Critical component in child’s development Isolation of premature baby and use of drugs in birth process may harm bonding process Some experts advocate a rooming-in arrangement while mother and child are in the hospital

The End