CHAPTER 9

STAGES OF PRENATAL DEVELOPMENT

GERMINAL STAGE

• The first two weeks after conception• The germinal stage spans the time from fertilization to implantation in the wall of the uterus.• For the first three or four days the mass of dividing cells moves about the uterus before implantation.

EMBRYONIC STAGE

• The period of 2 to 8 weeks after conception.•Major organ systems begin to take shape, which is now called the embryo.• Nervous system, head and blood vessels form at this time as well• During the 4th week, the heart starts beating

FETAL STAGE

• From the 9th week until birth.• All major organs as well as fingers and toes develop by the 12th week.• The fetus grows more than 30 fold in weight during the 2nd trimester (1 oz. to 2 lbs.)• The fetus reached the age of viability, where it could sustain life on its own outside of the womb.

THREATS TO PRENATAL DEVELOPMENT

•Maternal malnutrition is related to premature birth and low birth weight.

• The risk of spina bifida, a neural tube defect, can be reduced if vitamins containing folic acid are taken during pregnancy.

TERATOGENS

•Derived from the Greek root teras, meaning “monster”.•Can include;• Certain drugs taken by the mother• X-rays• Environmental contaminants such as

lead and mercury• Infectious organisms

TERATOGENS

• Can include infectious diseases such as rubella, which can lead to serious birth defects (heart disease, mental retardation, deafness)• HIV/AIDS and syphilis can be passed from mother to child during pregnancy.• Syphilis can lead to liver damage, impaired hearing and vision and deformities in teeth and bones.

SMOKING

• Can lead to miscarriage, premature birth, low birth weight and increased risk of infant mortality.• The more the mother smokes, the greater the risk.•Maternal smoking has also been linked to sudden infant death syndrome (SIDS)

SMOKING

•Maternal smoking can also lead to;• Lung problems• Childhood asthma• Developmental problems• Short attention span• Learning problems • Behavioral problems

ALCOHOL

•Maternal alcohol use can lead to fetal alcohol syndrome (FAS).• Alcohol is also the leading cause of mental retardation (facial deformities, underdeveloped upper jaw, widely spaced eyes).• There is no established “safe” limit for alcohol use during pregnancy

DRUGS

• Any drug used during pregnancy, whether legal or illicit, or any medication, whether prescribed or bought over the counter can potentially harm the fetus.

• Pregnant women should consult their doctors before taking any medication!