PRENATAL AND NEWBORN
DEVELOPMENT
RG 9c
CONCEPTION
●when male’s sperm fertilizes female’s egg
o At this point, the egg blocks all other sperm
o Women are born with all the eggs they will ever
have (1/5000 actually mature)
o Men begin producing sperm at puberty and
produce it 24/7 for the rest of their life
GENETICS
●This new one-cell entity contains 23 pairs of
chromosomes…one member of the pair
from the mother and the other from the
father
o Each chromosome contains thousands of
genes…either individually or in combination,
genes produce the particular characteristics of
each person
GENETICS
● Genes are composed of sequences of DNA
(deoxyribonucleic acid) molecules
● Some genes are responsible for the development of
systems common to all humans (heart,
circulatory
system, brain, lungs, etc.), while others control
characteristics that make each human unique (like eye
color, height, facial features, etc.)
● Sex is also determined by combination of genes
23rd chromosome)
(the
PRENATAL DEVELOPMENT
●Zygote – fertilized egg
oFewer than ½ survive the 1st 2 weeks
●Embryonic stage (weeks 2-8)
oAt 2 weeks, zygote becomes an embryo
oBy 4 weeks, embryo has developed a
rudimentary beating heart, brain and intestinal
tract (these organs are very primitive…but can
be recognized)
oBy 8 weeks, embryo is about an inch
long…has arms, legs and face that are distinct
ZYGOTE TO EMBRYO
6 days old
4 weeks
8 weeks
20 week fetus
20 week fetus
PRENATAL DEVELOPMENT
●Fetal stage (from 8 weeks to birth)
o At week 8, now called a fetus
o By around 4 months, fetal movement strong
enough to be detected by mother
o At around 6 months, eye lids open and fetus has
well-developed grasp and taste buds
PRENATAL DEVELOPMENT
● Fetus reaches age of viability or the point at which
it can survive if born prematurely at 24 weeks
(about 50% of premie babies survive at this age
and % increase as each week passes)
● Fetus continues to grow and gain weight during the
last two months…at the end of a normal 38 week
(9 ½ month) pregnancy, fetus typically weighs
around 7 lbs and is about 20 inches in length
PRENATAL INFLUENCES – GENETICS
● Genetic factors (major cause of genetic defects is faulty
genes or chromosomes)
o Phenylketonuria (PKU): protein builds up in the body. Digestive issues.
o Tay-Sachs disease: body is unable to break down fat, which causes these
substances to build up in and destroy brain and nerve cells, until the nervous
system shuts down
 babies usually start exhibiting signs of the disease around 4-6 months old
 children usually die by age of 5
 if parents both carry genetic defect, child has a 1 in 4 chance of being born
with the disease
 seems to occur most frequently in Central and Eastern European Jews
(and descendants)
o Down Syndrome
DOWN SYNDROME
●occurs when a zygote receives an extra
chromosome at the moment of
conception…causes mental retardation
(usually in the mild to moderate range)
o Often related to a mother’s age…more common in babies
born to mothers over the age of 35
o Characteristic facial features…including upward slanted
eyes, smaller noses, ears and mouth, and sometimes
smaller hands and shorter necks
o Often accompanied by other health problems…heart,
vision and hearing
ENVIRONMENTAL FACTORS
●Teratogens: environmental agents such as
drugs, chemicals, viruses or other factors
that can produce birth defects
o Mother’s illness
 Rubella (german measles) can cause
blindness, deafness, heart abnormalities and
stillbirth
 Syphilis can cause mental retardation,
physical deformities and miscarriage for
mother
 AIDS can be passed on to child prior to birth
ENVIRONMENTAL FACTORS
● Teratogens continued…
o Mother’s use of drugs
 Illegal drugs like cocaine can result in baby being born addicted to
the drug
 Even some legal drugs can cause fetal abnormalities
o Alcohol and nicotine use
 Fetal alcohol syndrome: condition resulting in mental and growth
retardation
 Some physical features associated with FAS – abnormally small,
small eyes and upturned nose, and small or abnormally formed
brain
 Most have some degree of mental retardation and many exhibit
problems with attention span, learning, coordination and behavior
 Smoking can lead to fewer nutrients received by the fetus which
results in lower birth weight…heavy smoking may affect the brain
NEWBORNS
●All babies are born with a number of reflexes
(unlearned, involuntary responses that occur
automatically in the presence of certain stimuli
 Rooting reflex – automatic turn of head when cheek is
touched
 Sucking reflex – suck anything that touches lips
 Startle reflex – infant flings arms, fans fingers and arches back
in response to sudden noise
 Babinski reflex – toes fan out when out edge of sole of foot is
stroked
 These reflexes are lost after first few months of age and
are replaced by more complex behaviors
NEWBORNS