67
Vernix caseosa 67
Age of viability 67
Teratogen 68
Sleeper effects 69
Fetal alcohol spectrum disorders 71
Fetal alcohol syndrome (FAS) 71
Spina bifida 75
Anencephaly 75
Prenatal care 77
Labor 79
Breech position 81
Cesarean section 81
Natural childbirth 81
Doula 81
Apgar scale 83
Brazelton Neonatal Behavioral Assessment Scale (NBAS) 83
States of arousal 84
REM sleep 84
Preterm 85
Small for date 85
Low birthweight 85
Very low birthweight 85
Extremely low birthweight 85
Kangaroo care 88
Summary
3.1 Describe the three periods of prenatal development.Conception occurs in the fallopian tube. During the germinal period, the zygote begins cell division and travels down the fallopian tube toward the uterus. During the embryonic period from weeks 2 to 8, the most rapid developments of the prenatal period take place. From 9 weeks until birth, the fetus grows rapidly, and the organs become more complex and begin to function.
3.2 Explain how exposure to teratogens and other environmental factors can influence the prenatal environment.Teratogens include diseases, drugs, and other agents that influence the prenatal environment to disrupt development. Generally, the effects of exposure to teratogens on prenatal development vary depending on the stage of prenatal development and dose. There are individual differences in effects, different teratogens can cause the same birth defect, a variety of birth defects can result from the same teratogen, and some teratogens have subtle effects that result in developmental delays that are not obvious at birth or not visible until many years later. Prescription and nonprescription drugs, maternal illnesses, and smoking and alcohol use can harm the developing fetus. Prenatal development can also be harmed by factors in the environment.
3.3 Summarize the process of childbirth.Childbirth progresses through three stages. The first stage of labor begins when the mother experiences regular uterine contractions that cause the cervix to dilate. During the second stage, the fetus passes through the birth canal. The placenta is passed during the third stage. Medication is used in most births, often in combination with breathing and relaxation techniques characteristic of natural births. About one-third of U.S. births are by cesarean section.
3.4 Discuss the neonate’s physical capacities, including development in low-birthweight infants.Developmental researchers now know that the newborn is more perceptually competent than ever imagined. The most well-developed sense is audition. Newborns display regular cycles of eating, elimination, and states of arousal or degrees of wakefulness, spending about 50% of their sleep time in REM, thought to permit the brain to stimulate itself. There are two types of low-birthweight infants, those who are preterm and those who are small for date. Low-birthweight infants struggle to survive. Low-birthweight infants experience higher rates of sensory, motor, and language problems as well as learning disabilities, behavior problems, and deficits in social skills into adolescence. The long-term outcomes of low birthweight vary considerably and depend on the environment in which the children are raised.
Review Questions
3.1 What are the three periods of prenatal development?What major milestones occur in each period?What are influences on prenatal care?
3.2 Define and provide three examples of teratogens.What are four principles that determine the effects of exposure to teratogens during prenatal development?
3.3 What are the three stages of childbirth?Describe characteristics of each stage.What are the differences among cesarean delivery, natural childbirth, and home birth?
3.4 How are neonates assessed at birth?Describe the neonate’s perceptual capabilities.What are two types of low-birthweight infants?What factors determine long-term outcomes for low-birthweight babies?
Descriptions of Images and Figures
Back to Figure
The parts labelled in the illustration are as follows.
Ovaries
Fallopian tube
Follicles
Corpus luteum
Uterus
Uterine wall
Cervix
Vagina
Back to Figure
The parts labelled are as follows.
Ovary
Corpus luteum[EI1]
Developing follicles
Ovulation
Fallopian tube
Fertilization (near the head of the Fallopian tube)
Cell division begins
Morula (where it enters the uterus)
Blastocyst with a noticeable inner cell mass
Implantation
Back to Figure
The details of the chart are as follows.
Weeks 1 and 2
Period of dividing zygote, implantation, and bilaminar embryo
Not susceptible to teratogenesis
Death of embryo and spontaneous abortion common
Weeks 3 to 8: Main embryonic period (in weeks)
Period of major congenital anomalies
Weeks 9 to 38: Fetal period (in weeks)
Period of functional defects and minor anomalies
Less Sensitive period:
Neural tube defects: weeks 3 to 6
Mental retardation: weeks 7 to 16
T A, A S D, and V S D: third week to sixth week
Amelia/Meromelia: weeks 4 to 5
Cleft lip: weeks 5 and 6
Low-set malformed ears and deafness: weeks 4 to 9
Microphthalmia, cataract, glaucoma: weeks 4 to 8
Enamel hypoplasia and staining: weeks 7 and 8
Cleft palate: weeks 7 to beginning of 9
Masculinization of female genitalia: middle of 7th week to week 9
Highly sensitive period:
C N S: weeks 32 to 38
Heart: end of week 6 to week 8