Читать книгу Infants and Children in Context - Tara L. Kuther - Страница 191

 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.