- Describe the stages of prenatal development and the significance of prenatal care
- Describe infant reflexes
- Explain the physical development that occurs from infancy through childhood
- Explain key milestones in Piaget’s sensorimotor and preoperational stages
- Explain key milestones in Piaget’s concrete operational and formal operational stages
Developmental psychologists study how people grow in three major areas: physical, cognitive, and psychosocial development. Just as Erikson outlined psychosocial stages across the lifespan, we can also look at physical and cognitive development in stages—from prenatal development to infancy, childhood, adolescence, and adulthood.
Prenatal Development
There are three stages of prenatal development: germinal, embryonic, and fetal. Let’s take a look at what happens to the developing baby in each of these stages.
Germinal Stage (Weeks 1–2)
Prenatal development begins at conception, when the sperm fertilizes the egg to form a zygote—a one-cell organism containing all the genetic material that determines sex and inherited traits.
During the first two weeks:
- The zygote divides repeatedly through mitosis (2 cells → 4 cells → 8 cells → …). This is a fragile process, and fewer than one-half of all zygotes survive beyond the first two weeks (Hall, 2004).
- As the cells divide, they become more specialized.
- In the germinal stage, the mass of cells has yet to attach itself to the lining of the uterus.
Embryonic Stage (Weeks 3–8)
After the zygote divides for about 7–10 days and has 150 cells, it travels down the fallopian tubes and implants itself in the lining of the uterus. Upon implantation, this multi-cellular organism is called an embryo.
Key developments during this stage:
- The placenta forms and connects to the uterus, providing nutrients and oxygen.
- Major structures—head, chest, abdomen—begin to develop.
- The heart starts beating, and vital organs begin to function.
- The neural tube forms, which will become the brain and spinal cord.
Fetal Stage (Weeks 9–40)
By nine weeks, the organism is called a fetus. Development continues rapidly through distinct periods:
- Weeks 9-12: The fetus reaches kidney bean size. Sex organs begin differentiating, and the “tail” disappears. Fingers and toes are fully developed.
- Week 16: The fetus measures approximately 4.5 inches long. Fingerprints are visible.
- Week 24 (6 months): The fetus weighs up to 1.4 pounds. Hearing has developed, allowing the fetus to respond to sounds. The internal organs—lungs, heart, stomach, and intestines—have formed enough that a fetus born prematurely at this point has a chance to survive outside the womb.
- Weeks 16-28: Throughout this period, the brain continues to grow and develop, nearly doubling in size.
- Week 36: The fetus is almost ready for birth. It weighs about 6 pounds and is about 18.5 inches long.
- Week 37 onward: By week 37, all of the fetus’s organ systems are developed enough that it could survive outside the uterus without many of the risks associated with premature birth. The fetus continues to gain weight and grow in length until approximately 40 weeks. By then, the fetus has very little room to move around, and birth becomes imminent.
The Importance of Prenatal Care
During each prenatal stage, genetic and environmental factors can affect development. The developing fetus is completely dependent on the gestational parent for life.
Prenatal care encompasses medical care during pregnancy for both the gestational parent and the fetus. It plays a crucial role in promoting optimal development, monitoring overall health, early detection of potential risks, and providing essential education and guidance.
According to the National Institutes of Health, routine prenatal care reduces the risk of complications during pregnancy. People who are trying to become pregnant should discuss pregnancy planning with a healthcare professional. They may be advised to take a vitamin containing folic acid, which helps prevent certain birth defects, or to monitor aspects of their diet or exercise routines.
Prenatal Influences: Teratogens and Environmental Factors
Recall that when the zygote attaches to the wall of the gestational parent’s uterus, the placenta is formed. The placenta provides nourishment and oxygen to the fetus. Most everything the parent ingests, including food, liquid, and even medication, travels through the placenta to the fetus, hence the common phrase “eating for two.” Anything the gestational parent is exposed to in the environment affects the fetus; if they are exposed to something harmful, the child can show lifelong effects.
What Are Teratogens?
A teratogen is any environmental agent—biological, chemical, or physical—that causes damage to the developing embryo or fetus.
Alcohol
Alcohol is not safe to drink in any amount during pregnancy. It crosses the placenta and affects the fetus. Alcohol use during pregnancy is the leading preventable cause of intellectual disability in children in the United States (Maier & West, 2001).
Fetal Alcohol Spectrum Disorders (FASD) are a collection of birth defects associated with alcohol consumption during pregnancy, with life-long consequences ranging from minor to major.
Physical characteristics may include:
- Small head size
- Abnormal facial features (see Table 1)
Cognitive and behavioral effects may include:
- Poor judgment and impulse control
- Higher rates of ADHD
- Learning issues and lower IQ scores
These developmental problems persist into adulthood (Streissguth et al., 2004). Animal studies suggest that prenatal alcohol exposure may predispose a child to prefer alcohol later in life (Youngentob et al., 2007).
| Facial Feature | Potential Effect of Fetal Alcohol Syndrome |
|---|---|
| Head size | Below-average head circumference |
| Eyes | Smaller than average eye opening, skin folds at corners of eyes |
| Nose | Low nasal bridge, short nose |
| Midface | Smaller than average midface size |
| Lip and philtrum | Thin upper lip, indistinct philtrum |
Nicotine (Smoking)
Smoking is a teratogen because nicotine travels through the placenta to the fetus. When the gestational parent smokes, the developing baby experiences reduced blood oxygen levels. According to the Centers for Disease Control and Prevention (2013), smoking while pregnant can result in:
- Premature birth
- Low birth weight
- Stillbirth
- Sudden infant death syndrome (SIDS)
Other Drugs and Teratogens
Heroin, cocaine, methamphetamine, most prescription medicines, and many over-the-counter medications are teratogens. Babies exposed to these substances may experience withdrawal symptoms or exhibit physiological responses reflecting their prenatal experiences. Appropriate medical care and support are essential for their safety and well-being.
Other teratogens include radiation, viruses such as HIV and herpes, and rubella—though most people in the U.S. receive childhood vaccinations against rubella.
Critical Periods in Development
Each organ develops during a specific critical period or sensitive period in pregnancy when it is most vulnerable to damage. For example, research with primate models of FASD has demonstrated that alcohol exposure limited to day 19 or 20 of gestation can lead to significant facial abnormalities (Ashley, Magnuson, Omnell, & Clarren, 1999). Different brain regions also show sensitive periods when they are most susceptible to alcohol’s teratogenic effects (Tran & Kelly, 2003).
The “Crack Baby” Myth
In the 1980s, concerns about crack cocaine’s impact during pregnancy led to the term “crack babies.” Chasnoff (1989) found high premature birth rates among individuals living in poverty who had used cocaine during pregnancy. However, subsequent research showed that these infants did not experience the predicted long-term brain damage or severe developmental problems.
Problems with the Original Research
Chasnoff’s research focused on a specific group of individuals living in poverty who used cocaine—primarily low-income urban populations with multiple risk factors. Methodological limitations made it problematic to generalize the findings to the broader population of pregnant individuals using cocaine.
Harmful Consequences
The media’s portrayal of crack babies perpetuated anti-Black stereotypes, disproportionately affecting communities of color and reinforcing misconceptions that linked drug use to moral character. This focus on crack cocaine overshadowed other social factors contributing to substance abuse and obscured the broader context of maternal health. The crack baby myth perpetuated harmful stereotypes and overlooked systemic issues surrounding drug addiction and maternal well-being.
Ethical Considerations: Drug Use and Pregnancy
Addressing substance use during pregnancy requires thoughtful consideration of effective and ethical approaches to support pregnant individuals and promote the well-being of both mothers and children.
The Interagency Policy on Management of Substance Abuse During Pregnancy implemented in Charleston aimed to deter drug use through mandatory screenings and legal actions. However, it faced significant challenges and negative outcomes.
This policy seemed to deter pregnant people from seeking prenatal care, deterred them from seeking other social services, and was applied solely to low-income women, resulting in lawsuits. The program was canceled after 5 years, during which 42 women were arrested. A federal agency later determined that the program involved human experimentation without the approval and oversight of an institutional review board (IRB).
- What were the flaws in the program, and how would you correct them?
- What are the ethical implications of charging pregnant women with child abuse?