Warm up 8/31
• List everything that you know about
pregnancy and in-utero development.
Prenatal Development &
Complications
Fertilization
• Midway through
menstrual cycle –
ovulation occurs
• When sperm
penetrates egg all
other sperm are
repelled.
• Unified cell called a
zygote.
First Trimester
• Zygote (fertilization to three weeks)
• Embryo (fourth through eight weeks)
• Fetus (ninth week through birth)
– First trimester ends during the third month
– Second trimester ends during the sixth month
The zygote at
two different
stages of
development
The Germinal Period: First
21 Days
• Division of zygote
begins within 36
hours of fertilization
• Implantation in
uterus happens
about six days after
fertilization
The Germinal Period: First
21 Days
• During the third week of
the germinal period, the
zygote forms the
embryonic disc
– the ectoderm (skin and
nervous system)
– the mesoderm (muscles,
bones, and the circulatory,
excretory, and reproductive
systems)
– The endoderm (digestive
system and lungs)
– neural tube develops
(central nervous system)
The Embryo: Weeks Four - Eight
• Fourth week: head and blood vessels begin to
develop and heart begins to beat
• End of the first month: eyes, ears, nose, and
mouth start to form; buds that will become arms
and legs appear
– 1/5th inch long
• Second month: upper arms, forearms, hands,
and fingers appear, followed by legs, feet, and
toes; fingers and toes separate (no longer
webbed)
The Embryo: Weeks Four - Eight
• End of the second month: head is more
rounded, features of the face fully formed;
has all basic organs except sex organs;
buds for first baby teeth
– 1/30th ounce and 1 inch long
• All sex organs are the same
until the X or Y chromosome
calls for testes or ovaries
The Fetus: Weeks Nine - Birth
• Third month: muscles develop, cartilage
replaced by bone; all major organs complete
their formation, including stomach, heart, lungs,
and kidneys; sex organs take discernable
shape
• End of the third month: can move almost every
part of body (kicking legs, sucking thumb,
squinting, and frowning); has fully formed
fingerprints
– 3 ounces and 3 inches
Trimester Two
• Time for essential organ and brain maturation
• Hair, including eyebrows and eyelashes, begins
to grow
• Fingernails, toenails, and buds for adult teeth
form
Fetus at 23 weeks
Trimester Two
•
•
•
•
Fifth month: mother can feel the baby move
The brain increases sixfold in size
22 weeks: 22 ounces
26 weeks: 2 pounds
Trimester Three
• Time for final prenatal maturation
• Lungs begin to expand and contract so infant
can breath outside the womb
• Valves of the heart go through final maturation
• Brain development is also ongoing; at 34
weeks, distinct sleeping and waking patterns
can be measured
• Substantial weight gain (from approx. two
pounds to approx. 7.5 pounds)
Complications
• Diseases
– Rubella
– HIV
– Syphilis
– Genital herpes
• Drugs
– Alcohol
– Tobacco
– Heroin/Methadone
– Cocaine/Marijuana
Complications – Diseases
• Rubella
– Also called German measles
– Contracted early in pregnancy, may cause
blindness, deafness, heart abnormalities, and brain
damage
• HIV
– When a woman who carries the HIV virus becomes
pregnant, there is a 15 – 30% chance that her fetus
will become HIV-positive
– 50% of HIV-positive infants die by age three
Complications – Diseases
• Syphilis
– Can be cured with penicillin
– Disease-causing organisms cannot cross placenta
during first three months of pregnancy, so it’s
important for early treatment
– If not treated, fetus may die or suffer bone or brain
damage
• Genital herpes
– Can cause infant death, blindness, and mental
retardation
Complications – Drugs
• Alcohol
– Fetal Alcohol Syndrome (FAS)
• Estimated 3 out of 1,000 babies are born with FAS
– Distinctive symptoms: growth retardation; brain
damage; facial abnormalities (small heads,
abnormally spaced eyes,
flattened noses, low-set,
unparallel ears;
abnormalities of the skeleton
and joints
Complications – Drugs
• Tobacco
– Every puff of a tobacco product reduces the amount
of oxygen to the fetus and increases the toxins,
impeding nutrition
– Smoking during pregnancy increases the possibility
of lowered birth weight and shorter length
– Other possible complications: spontaneous
abortion, death in uterus, premature separation of
the placenta from the uterus, greater need for
intensive care, possibly asthma, cleft lip and palate
and lower scores on cognitive tests
Complications – Drugs
• Heroin/Methadone
– Babies born to addicted mothers are born addicted
as well
– Can possibly die of withdrawal symptoms if not
treated at birth
– Addicted babies more likely to suffer from learning
disabilities
– Other complications: low birth weight, jaundice,
breathing difficulties,
Complications – Drugs
• Cocaine/Marijuana
– Possible complications include premature labor and
more time spent in intensive care, restricted blood
flow to the placenta, resulting in poorer prenatal
brain development, and babies who are quick to
start and slow to adjust to the sights and sounds
around them
– Cocaine users are more likely to have premature
babies with low birth weights and attention
problems
– Heavy marijuana use can lead to sleep
disturbances and premature birth