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Module 4

1. Module 4

1.11. Page 4

Lesson 2

Module 4—From Fertilization to Birth

Lesson Summary

 

The following focusing questions were addressed in this lesson:

  • What are the major events of each trimester?

  • What is the significance of the first trimester?
  • What is the significance of the effects of teratogens on embryonic and fetal development?

Prenatal development is divided into three trimesters and two developmental periods. Embryonic development begins at fertilization and ends after about the eighth week of pregnancy. Fetal development begins at the ninth week and continues until birth. Both embryonic and the first events of fetal development occur within the first trimester. The first trimester is the time when the developing embryo and, later, the fetus are most vulnerable to improper nutritional requirements and exposure to harmful teratogenic agents. This is the time when the most sensitive embryonic and fetal development is taking place. The fetal development period consists of significant events related to the progressing months of pregnancy. Most of the fetal development period is occupied by further development of the organ systems. Understanding the significant developmental events that occur during pregnancy helps doctors and parents follow the development of the maturing fetus right up until birth.

 

Refer to “Table 15.2” on page 521 of the textbook for a review of the major events in prenatal development.

 

Lesson Glossary

 

fetal alcohol spectrum disorder: a permanent syndrome of birth defects caused by maternal intake of alcohol during pregnancy; includes disorders of growth, behaviour, and cognitive abilities

 

folic acid (folate): Vitamin B9; ingestion prior to and during pregnancy prevents neural tube defects, such as spina bifida

 

lactation: the production and secretion of milk from the breast; also known as “nursing”

 

parturition: childbirth or labour

 

prenatal: before birth

 

teratogen: a substance or other factor that can cause developmental abnormalities during fetal development; e.g., chemicals, viruses, or radiation

 

trimester: one-third of the gestational period

 

There are three trimesters of pregnancy.

 

vernix: a cheesy, oily substance covering the fetus; has antibacterial properties