Child Development From Infancy to Adolescence. Laura E. Levine
alt="A person holding the hand of a new born baby between the first three fingers."/>
grandriver via Getty Images
Test Your Knowledge
Test your knowledge of child development by deciding whether each of the following statements is true or false, and then check your answers as you read the chapter.
1 T□ F□ A woman is more likely to miscarry a pregnancy if she is carrying a male fetus.
2 T□ F□ Using techniques that are available today, it is possible for some parents to choose the sex of their baby with 100% accuracy.
3 T□ F□ Research has shown that exposing a fetus to extra stimulation (for example, playing music near the pregnant woman’s stomach) can stimulate advanced cognitive development.
4 T□ F□ A pregnant woman is “eating for two” so she should double the number of calories she consumes each day.
5 T□ F□ The amount of alcohol that a woman consumes while she is pregnant doesn’t matter because all amounts of alcohol are equally harmful to the infant.
6 T□ F□ Children who were exposed to marijuana prenatally are more likely to smoke marijuana when they become teenagers.
7 T□ F□ The rate of maternal mortality in the United States is increasing.
8 T□ F□ An infant who is born prematurely will have developmental problems and lag behind other children of the same age.
9 T□ F□ When a woman gives birth she instinctively knows what to do to care for her new baby.
10 T□ F□ Following the birth of a baby, couples today pretty much share household and child care responsibilities equally.
Correct answers: (1) F, (2) T, (3) F, (4) F, (5) F, (6) T, (7) T, (8) F, (9) F, (10) F
Learning Questions
4.1 What happens during the three stages of prenatal development?
4.2 What are some risks and health issues during pregnancy?
4.3 What happens during the process of labor and delivery?
4.4 How do newborns function, and what threatens their well-being?
4.5 How do people experience the transition to parenthood?
From the moment a sperm unites with an egg in the process of fertilization, the complicated process of development begins. As you learned in Chapter 3, that moment determines the genetic makeup of the new individual, but from that very moment the fertilized egg, or zygote, also begins interacting with the environment. What happens in the prenatal environment of a woman’s womb over the next 9 months has a tremendous effect on the course of development. As you’ll see in this chapter, the process has some built-in safeguards that help ensure the newborn is healthy and fully ready to enter the world, but the system is not perfect, and the number of potential prenatal threats is substantial. Fortunately, we know a great deal today about ways to help a mother go through her pregnancy without complications and get the newborn off to the best possible start in life.
In this chapter, we describe the process of prenatal development. We also look at the experience of birth from the perspective of the parents and infant and see how the couple handles the transition to becoming a family.
The Three Stages of Prenatal Development
>> LQ 4.1 What happens during the three stages of prenatal development?
We begin by looking at the process of prenatal development, describing how, over the period of 9 months, a single fertilized cell develops into a fully formed and functional newborn. We also look at how assistive reproductive technology can help couples who are dealing with infertility.
The prenatal journey begins when a follicle in a woman’s ovary matures and releases an ovum or egg during her monthly menstrual cycle in the process called ovulation. The ovum begins to travel down the fallopian tube toward the uterus. This is where fertilization occurs, when the egg is penetrated by one of the approximately 300 million sperm cells released into the woman’s reproductive system during an act of intercourse. Usually only one child is conceived at a time, but as you learned in Chapter 3, multiple births can also occur.
Ovum: An unfertilized egg.
Ovulation: The release of a mature egg from an ovary.
Although the ratio of male–to-female conceptions has been a topic of debate for a number of years, the best current evidence is that there are an equal number of male and female conceptions (Orzack et al., 2015). Although more male than female fetuses are lost in the early weeks of a pregnancy and again near the end, the overall rate of loss during the prenatal period is higher for female fetuses (Orzack et al., 2015). Consequently, by the time babies are born, the number of males exceeds the number of females. In some countries, the selective abortion of female fetuses increases the worldwide male-to-female ratio even more (United Nations Population Fund, 2017).
T/F #1
A woman is more likely to miscarry a pregnancy if she is carrying a male fetus. False
Prenatal development is divided into three stages of very different lengths. We next describe what happens in each of these stages in detail.
The Germinal Stage (Conception to 2 Weeks)
The first stage of prenatal development, called the germinal stage, begins when the sperm penetrates the egg. Once fertilization occurs and there is a zygote or fertilized egg, the outside thickens so no other sperm will be able to enter. As the zygote continues the journey through the fallopian tube, the process of cell division begins (see Figure 4.1). It takes about 15 hours for that single cell to become 2 cells, and then the process continues with 2 cells becoming 4, then 8, and so on until there is a ball of 32 cells at 4 to 5 days following conception, which is then ready to implant in the lining of the uterus. During the woman’s menstrual cycle, her hormones have prepared the lining for just this purpose. If the ball of cells fails to implant for any reason, it passes out of the woman’s body without her even realizing there had been a conception. This is not at all uncommon. In fact, it is estimated that close to 50% of conceptions fail to implant and do not survive (Brosens et al., 2014).
Germinal stage: The prenatal stage that lasts from conception to 2 weeks postconception.
Figure 4.1 The germinal stage.
Source: BFIP/Photo Researchers, Inc.
As the cells continue to proliferate, the solid ball becomes a hollow ball called a blastocyst, which has a group of cells at one end called the inner cell mass and an outer ring of cells called the trophoblast (see Figure 4.2). The inner cell mass will go on to become the embryo and part of the amnion that surrounds the embryo, and the outer ring will become the support system for the pregnancy, which includes the placenta and the chorion. We describe these structures and their functions in the next stage of prenatal development.
Blastocyst: A hollow ball of cells that consists of the inner cell mass, which becomes the embryo, and an outer ring of cells, which becomes the placenta and chorion.
Inner cell mass: A solid clump of cells in the blastocyst, which later develops into the embryo.