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Developmental Psychology 101: Prenatal Development and Birth


The Developmental Psychology 101 series addresses the theories, periods, and implications of development in a human life from conception all the way through to the stage of adolescence. Developmental psychology is a field which is studied by psychology students and academic researchers; its purpose is to understand individuals based on the biological and psychological changes they experience throughout their lifespan. Development is defined as modifications that momentarily or permanently change an organism in the journey from conception to death (Cole et al., 2005). This 101 series of articles will refer to development from a psychological perspective, discussing its social, emotional, cognitive, and physical areas. Moreover, the debate of nature versus nurture will be discussed in the development of the following four stages of life: prenatal period, infancy, childhood, and adolescence.

The Developmental Psychology 101 series is divided into six chapters:

1. Developmental Psychology 101: Theories of Development

2. Developmental Psychology 101: Methods of Studying Development

3. Developmental Psychology 101: Prenatal Development and Birth

4. Developmental Psychology 101: Development in Infancy

5. Developmental Psychology 101: Development in Childhood

6. Developmental Psychology 101: Development in Adolescence

Developmental Psychology 101: Prenatal Development and Birth

For all living things, development begins with conception. This article strives to answer the following question: in the fight between nature and nurture, does the environment influence a developing fetus, or, at this stage, does nurture win? This question has an incredible importance in the field of developmental psychology, as the human in the prenatal period seems to be highly influenced by the pregnant person’s feeding habits, health, use of substances, stress levels, and many more aspects (Cole et al., 2005, p. 80). However, the genetic aspect influences development as the growth of the organism happens. For these reasons, both nature and nurture have an effect on a developing fetus.

Figure 1: Pregnancy representation (Houle, 2011).

For humans, existence begins at the zygote stage. A zygote is a fertilized cell that results from the harmonic fusion of a female gamete, or egg, and a male gamete, or sperm (Merriam-Webster., n.d.). The transformation of the zygote that activates development is found in the first cell divisions. There are three main periods categorized under the prenatal development stage of life (Cole et al., 2005, p. 81). The first stage is the germinal period that begins with conception, thus forming the zygote, and lasts for about 8 to 10 days, up until the cell attaches itself to the uterine wall. The second stage, the embryonic period, begins with this attachment and lasts until the eighth week of existence. While in the embryonic period, the organism grows and some of its organs start shaping. The last stage is the fetal period. At this stage, the organism starts hardening the bones, and it keeps growing until the baby can exist outside the pregnant person’s body. During any of these stages, development can suddenly come to an end. Wilcox et al. (1999), the researcher who studied the timeline of implantation in pregnancy, estimates that approximately 25% of pregnancies end before one even realizes they are pregnant.

Physical Development and Growth Inside the Uterus

The germinal period is the shortest period in prenatal development, and it represents the cell division of one cell until an embryo is formed through the process called mitosis. As the developing cell moves into the uterus, the next phase of the germinal period takes place. The implantation of the cell is the process in which the growing organism gets attached to the uterine wall. This is one of the most common stages in which a spontaneous termination of pregnancy can occur, as the pregnant body can negatively react to the implantation, a reaction which results in miscarriage (Cole et al., 2005, p. 82).

Figure 2: Stages of prenatal development (Iowa State University Digital Press, n.d.)

However, once the implantation is complete, the embryonic period begins. Between days 10 and 13 of the pregnancy, the cells separate into three layers. The first one is the ectoderm which later on separates into the outer surface of the skin, part of the teeth, the nails, the lens of the eye, the inner ear, and the central nervous system. The second layer is the endoderm, from which the digestive system and the lungs begin their formation. The third layer to appear is the mesoderm, which will eventually become bones, muscles, the inner parts of the skin, and the circulatory system (Gilbert, 2001). In the third week of pregnancy, the primal version of the brain is formed as well as primitive blood vessels and cells. The heart begins forming, and, by the end of this stage, it starts beating. By the sixth week, the major veins and arteries are formed, nerves appear in their primordial form, pre-muscle masses begin forming, the head grows as the lower jawbone fuses, and the external ears appear.

In the seventh week of the pregnancy, the face and the neck of the embryo begin to differentiate, the stomach and muscles move toward their final forms and positions, and the brain starts developing nerve cells. In this embryonic period of development, sexual differentiation occurs. In the seventh week, the embryo that is genetically male, due to it having an XY pair of chromosomes, begins to form testes from the gonadal ridges (Ostrer et al., 2007). The gonadal ridges of the organism with an XX pair of chromosomes do not change until the ovaries begin to form a few weeks later. Taking into consideration the existing gender stereotypes, the current scientific facts cannot ascertain that gendered behavior is a result of this separation of chromosomes; therefore, it cannot be confirmed that this genetic separation in the seventh week affects the play preferences of the child or any other aspects of the grown adult the embryo is to become (Jordan-Young, 2010). By the eighth week, the embryo is already capable of some movement (Cole et al., 2005, p. 84).

Figure 3: Physical development in stages (Cherry, 2020)

In the fetal period of prenatal development, the bones of the fetus start hardening, and the fetus continues growing until birth. In this stage, the baby grows in length from approximately 4 centimeters to 51 centimeters and in weight from approximately 0.09 kilograms to 3.2 kilograms (Cole et al., 2005, p. 85). It is important to note that in this period the fetus develops sensory capacities. This development already seems to influence the baby’s development with external factors, even before having been born. The fetus starts feeling changes in the pregnant person’s posture and adjusts itself accordingly at about five months into the pregnancy (Lecanuet & Jacquet, 2002). At 26 weeks after conception, the fetus can perceive light if it is held on the carrier’s belly, and it starts responding to sounds between the fifth and the sixth month of the pregnancy (Lecanuet & Schaal, 1996; Abrams et al., 1998). However, interestingly, the fetus can already recognize changes in sound between the sixth and seventh week after conception (Draganova et al., 2007). Moreover, the baby can be startled at around eight weeks after conception, starts breathing and stretching at around ten weeks, yawns at around eleven weeks, and can suck and swallow after twelve weeks (De Vries et al., 1982).

Environmental Effects on Prenatal Development

There are many behaviors and attitudes that a pregnant person can display during their pregnancy, and these can affect the way the fetus develops prenatally. Researcher and professor emeritus at the Hebrew University’s School of Pharmacy-Institute for Drug Research, Marta Weinstock (2005) has proven that the effects stress has on the pregnant person can have long-lasting effects on the baby. Professor of Biobehavioral Health at Pennsylvania State University, Elizabeth Susman and her team (2001), discovered that children born to people who had stressful environments while pregnant were more aggressive than children whose carrier did not produce elevated levels of cortisol because of stress. In 2010, professor at the UCI School of Medicine Claudia Buss, and her team of researchers, discovered that the pregnant person’s perceived anxiety in regard to pregnancy in the first trimester affected the normal development of gray matter in some areas of the baby’s brain. The reduction of the gray matter generated a lower IQ for the people that participated in this study due to the fact that this network of the brain is involved in processing information and contains nerve cells that contribute to the development of intellect.

Figure 4: Baby ultrasound (VeryWellFamily, 2021).

Another aspect of the environment to consider is a pregnant person’s nutrition. Studies show that poor maternal nutrition can lead to either miscarriage or lower weight of the baby after birth, which can imply that the baby has not yet developed completely and needs to be under supervision after birth (Mora & Nestel, 2000; Morton, 2006). In 1982, a study done by Dr. Lou Hicks, PhD, a research affiliate at Tulane University, and a team of researchers proved that food supplements taken in the first three months of the pregnancy can lead to an increase in the baby’s postnatal intellectual development. On the other hand, overnourished pregnant people can give birth to children who later in life develop obesity and diabetes (Baker et al., 2008). Although the effects of poor nutrition or overeating during pregnancy are correlational with the possible after-birth issues that can affect the baby, they should not be considered the biggest cause of diseases that might develop later in life (Cole et al., 2005, p. 93).

When discussing environmental effects, one must consider teratogens. These are “environmental agents such as toxins, disease, drugs, and alcohol that increase the risk of deviations in normal development and can lead to serious abnormalities or death” (Cole et al., 2005, p. 94). There are many studies done on the effects of numerous teratogens on prenatal development. This article will only focus on a few agents. Alcohol is one of the main agents that affect children in prenatal development as well as during their later lives (Molina et al., 2007). A fetus that has been exposed to substantial amounts of alcohol is in danger of being born with serious problems, including fetal alcohol syndrome that leads to an underdeveloped brain, congenital heart disease, and bodily malformations (O’Leary et al., 2010).

Figure 5: Nutrition in pregnancy (Riverside, N/A)

Drug use, such as cocaine use, can lead to premature births, possible strokes that the baby might have after being born, and birth defects if the drug is used while pregnant (Ursitti et al., 2001). The most common long-lasting effect on children that have been exposed to cocaine prenatally is difficulty in regulating emotions and irritability, or reactivity to environmental situations (Schuetze et al, 2009; Morrow et al., 2003). There are also a number of diseases that can be transmitted from a pregnant person to a baby in the process of giving birth such as AIDS and hepatitis. These conditions can endanger the baby and greatly affect their quality of life growing up (Cole et al., 2005, p. 100). All in all, the pregnant person’s lifestyle could influence prenatal development as well as the formation of preferences and personalities of the fetus after birth.

The process of giving birth can be stressful for both the person giving birth and the child. Hugo Lagercrantz and Theodore Slotkin (1986), two scientists passionate about development, postulate that stress is of utter importance for the baby’s adaptation to the world outside the womb. First of all, the released hormones of the baby at birth raise the baby's metabolic rate, thus increasing blood flow which helps the lungs and the brain to function properly. Second of all, as the baby adjusts to the new breathable air outside of the womb, breathing regulation becomes the most important action in raising alertness and beginning the process of learning. After birth, one of the most important aspects of a child’s development is the relationship that is formed with the parents. “Babyness” was discussed in a previous article, and it is one of the observed factors that influence this relationship. It was observed that parents who do not perceive their babies as “cute” are more likely to pay attention to other people in the room rather than to the baby (Langlois et al., 1995). Additionally, this relationship seems to either improve or remain stagnant based on the sex of the baby and the parent’s expectations and societal values; whether they wanted a boy or a girl influences how the parents perceive the baby (Basow, 2006).

Figure 6: Timeline of teratogens effects (Dunbar, n.d.)


Gender roles and stereotypes seem to be attached to a baby immediately after birth, but what about before its journey into this world? This article discussed whether nature or nurture influences a human prenatally and in what way. Clearly, genetics play their part, and the fetus is created by duplicating part of their blood relations’ DNA. Nature contributes to the development of sex inside the womb, and later on in life, the gender of the baby as well as their socially learned traits and inclinations. The way in which a pregnant person takes care of their physical and mental health during pregnancy clearly seems to influence prenatal development. Substance abuse, diseases, and stress can lead to losing the baby or giving birth to a malformed fetus. Hence, the conclusion is that nature and nurture both have an effect on prenatal development. The stages of development are almost always the same, playing out in the same order, and always affecting the development of the fetus and the baby. However, the child cannot be separated from the pregnant person’s body. This is the moment when the clear boundaries between the effects of nature and those of nurture become blurry, as the baby will always be affected by the habits of the pregnant person. Adults have a responsibility that starts prenatally, not just after birth, and the caregivers have an enlarged effect on how a child grows up and who they become.

Bibliographical References

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Basow, S. A., Phelan, J. E., & Capotosto, L. (2006). Gender patterns in college students' choices of their best and worst professors. Psychology of Women Quarterly, 30(1), 25-35.

Buss, C., Davis, E. P., Muftuler, L. T., Head, K., & Sandman, C. A. (2010). High pregnancy anxiety during mid-gestation is associated with decreased gray matter density in 6–9-year-old children. Psychoneuroendocrinology, 35(1), 141-153.

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Visual Sources

Cover image: Akeni, K. (2013). Womb's eye [Painting]. Retrieved from:

Figure 1: Houle, G. J. (2011). Baby belly art [Photo]. Retrieved from:

Figure 2: Iowa State University Digital Press. (N/A). Prenatal development [Illustration]. Retrieved from:

Figure 3: Cherry, K. (2020). Stages of prenatal development [Illustration]. Retrieved from:

Figure 4: Very Well Family. (2021). Ultrasound images of your growing baby boy [Photo]. Retrieved from:

Figure 5: Riverside. (N/A). Nutrition during pregnancy: Healthy recommendations [Photo]. Retrieved from:

Figure 6: Dunbar, J. (n.d.). Teratogen. What Is It, Examples, and More [Illustration]. Retrieved from: