Wednesday February 12 2014 Developmental Psychology Chapter 4 The Prenatal Period and Birth Nature and Nurture Prenatal development is the product of complex interactions involving genetic instructions inherited from parents and the expectant woman s physical and emotional conditions as well as exposure to drugs diseases hazardous chemicals and medications before and during pregnancy and during labor We have seen for example that differentiation of organs and systems in the embryo typically obeys principles established by biochemical and physiological processes Yet these processes do not operate in a vacuum Teratogens and various intrauterine conditions can radically alter the normal developmental path Thus events in the life of the woman may change the immediate environment within her womb with drastic consequences for the fetus Sociocultural Influence The immediate internal environment of the fetus and the perinatal environment provided for the newborn can be influenced dramatically by the larger social economic and cultural settings in which pregnancy and birth take place The woman s actions during pregnancy are often modified or regulated by a network of expectations advice and resources within the culture in which she lives An expectant woman in one community for example may have access to medical and other kinds of care that provide a more healthy environment for the fetus than a woman in another community Industry or governmental units may legislate controls on chemical pollution in one country and ignore them in another Scientific and technological advances in prenatal testing birthing practices and newborn care may be available in one region of the world but not in another even when available however not all parents may have the economic resources or the desire to use them 1 Wednesday February 12 2014 Continuous Discontinuous When the zygote attaches to the uterine wall and taps a new source of nourishment its course of development changes dramatically Once the various organs and systems are formed and become less susceptible to environmental disruptions the fetus achieves a vastly different status The process of birth itself is a major transition Such spectacular changes fit with discontinuous or stage like descriptions of development So do the marked shifts in vulnerability to teratogens observed during prenatal development Underlying the progressions however are biochemical and physiological processes governing cell proliferation differentiation and the emergence and functioning of biological systems that can be seen as continuous Many dramatic changes are essentially the product of modest accumulative modifications in the multifaceted complex environment that promotes development Risk Resilience Newborns everywhere undergo many common gestational experiences however differences in development arise because the fetus is not immune to the influences of the larger world Because of exposure to teratogens and other maternal conditions babies will differ in their physical and behavioral qualities and their ability to cope with and adapt to their new environment Low birth weight for example is an important element in increasing risk for a newborn Greater knowledge of and sensitivity to those differences by caregivers whether exhibited by a newborn with special needs such as one with low birth weight or by an infant who falls within the typical range for newborns can help to ensure success for the continued development of every child The Stages of Prenatal Development The prenatal period extends from conception to birth The perinatal 2 period extends from about the seventh month of Wednesday February 12 2014 pregnancy until 28 days after birth The postnatal period is the time that follows birth Fertilization normally takes place in the Fallopian tube when an ovum or egg cell in penetrated by a single sperm cell During the germinal period about the first ten to fourteen days after conception the zygote migrates from the Fallopian tube to the uterus becomes multicelled and implants itself in the uterine wall to gain access to a new source of nutrients obtained from the mother The embryonic period is marked by development of the placenta and other supportive structures within the uterine environment and by the differentiation of cells into tissues that form the major organs and systems of the embryo The fetal period beginning in about the eighth week after conception and lasting until birth is marked by substantial growth and by refinement of organs and systems By the last trimester the ability of the fetus to survive on its own viability improves For human infants birth typically occurs around 274 days gestational age The major body organs and systems including the brain and nervous system differentiate during the embryonic phase Neurons continue to form and migrate during the fetal period Brain activity sensory reactions and movement are exhibited by the fetus Among the assisted reproduction technologies and associated procedures used to facilitate the birth of offspring are artificial insemination by donor egg donation fertility drugs gamete intrafallopian transfer in vitro fertilization and maternal surrogacy Some of the issues raised by these technologies include the competence of the practitioners the fact that children born with these methods may not know about their biological heritage and the increased risk associated with multiple pregnancies that result from such procedures Environmental Factors Influencing Prenatal Development 3 Wednesday February 12 2014 The placenta serves as the major organ for transfer of nutrients from the mother s circulatory system and for expelling waste products from the fetus The umbilical cord connects the fetus to the placenta The amniotic sac provides a fluid filled protective surrounding in which development of the fetus occurs During both the embryonic and fetal development teratogens or environmental agents harmful to the organism can disrupt development and interfere with later behavior The effects of teratogens differ depending on the genetic susceptibility of the embryo or fetus how the teratogen reaches the prenatal environment its level of dosage and manner of exposure and where it interferes with cellular activity A teratogen s effects also differ depending on the time at which exposure occurs during prenatal development Not all the consequences are observed immediately they may not even be evident until well into the