Transcript FETAL GROWTH & DEVELOPMENT

FETAL
DEVELOPMENT
Peggy Pannell RN, MSN
Learning Goals
• Normal Fetal Development
– From ovulation to birth
• Teratogen
– Definition and potential effects on
development
Vocabulary
•
•
•
•
•
•
•
•
•
Blastocyst
Conception
Ductus arteriosus
Embryo
Fertilization
Fetus
Foramen Ovale
HCG
Implantation
•
•
•
•
•
•
•
•
•
L/S ration
Gestational age
Vernix
Zygote
Placenta
Quickening
Surfactant
Teratogens
Umbilical Cord
FERTILIZATION
• Begins with 46 pair of chromosomes,
splits off to 23 then combine for a unique
new 46 pair.
Stages and Time Frames
• Ovum
• Zygote
• Morula
• Blastocyst
• Embryo
• Fetus
(Oh, Zee my baby
eats fast)
IMPLANTATION
First weeks of human development:
Blastocyst embedded in endometrium.
PRIMARY GERM LAYERS
• Ectoderm
• Mesoderm
• Endoderm
GESTATIONAL AGE
• Gestational age=Time since last menstrual period
(LMP)
• EDC, EDD, EDB
• 266 Days after fertilization
• 280 Days after onset of LMP
Days
Weeks
Calendar Months
Lunar Months
Fertilization
266
38
8 3/4
9 1/2
LMP
280
40
9
10
GESTATIONAL AGE
Nagele’s Rule
• Add 7 days to the first day of the last
normal menstrual period, subtract 3
months and add 1 year.
• Example:
–
–
–
–
1st day of LNMP=December 16 2006
add 7 days = Dec. 23 2006
subtract 3 months = Sept 23 2006
add 1 year =Sept 23 2007, estimated due date
(EDD)
TRIMESTERS
Trimester
1st = week’s 1-13
2nd = week’s 14 - 26
3rd = week’s 27 and on
(38-40 WEEKS)
STAGES OF DEVELOPMENT
FETAL MEMBRANES
Decidua basalis
• Amnion
• Chorion
Developing placenta
Yolk sac
Amniotic cavity
Decidua capsularis
Intrauterine cavity
Decidua vera
Mucus plug
(operculum)
Villi of fetal
portion of
placenta filled
with fetal blood
Intrauterine cavity
Decidua capsularis
Decidua
vera
Lacunae in decidua
basalis filled with
maternal blood
Umbilical cord
(funis)
Membranes:
Amnion (blends
with umbilical cord)
Chorion (blends with placenta)
1 Month
• First Trimester
At the end of four weeks:
• Baby is 1/4 inch in length
• Heart, digestive system,
backbone and spinal cord
begin to form
• Placenta (sometimes called
"afterbirth") begins to
develop
• The single fertilized egg is
now 10,000 times larger
than size at conception
Month 2
• First Trimester
At the end of 8 weeks:
• Baby is 1-1/8 inches long
• Heart is functioning
• Eyes, nose, lips, tongue,
ears and teeth are forming
• Penis begins to appear in
boys
• Baby is moving, although
the mother can not yet feel
movement
Month 3
•
•
•
•
•
•
•
•
First Trimester
At the end of 12 weeks:
Baby is 2 1/2 to 3 inches long
Weight is about 1/2 to 1 ounce
Baby develops recognizable form.
Nails start to develop and
earlobes are formed
Arms, hands, fingers, legs, feet
and toes are fully formed
Eyes are almost fully developed
Baby has developed most of
his/her organs and tissues
Baby's heart rate can be heard at
10 weeks with a special
instrument called a Doppler
Month 4
•
•
•
•
•
•
•
•
•
•
Second Trimester
At the end of 4 months:
Baby is 6 1/2 to 7 inches long
Weight is about 6 to 7 ounces
Baby is developing reflexes, such
as sucking and swallowing and
may begin sucking his/her thumb
Tooth buds are developing
Sweat glands are forming on
palms and soles
Fingers and toes are well defined
Sex is identifiable
Skin is bright pink, transparent
and covered with soft, downy hair
Although recognizably human in
appearance, the baby would not
be able to survive outside the
mother's body
Month 5
• Second Trimester
At the end of 5 months:
• Baby is 8 to 10 inches long
• Weight is about 1 pound
• Hair begins to grow on baby's
head
• Soft woolly hair called lanugo
will cover its body. Some may
remain until a week after
birth, when it is shed.
• Mother begins to feel fetal
movement
• Internal organs are maturing
• Eyebrows, eyelids and
eyelashes appear
Month 6
• Second Trimester
At the end of 6 months:
• Baby is 11 to 14 inches
long
• Weight is about 1 3/4 to 2
pounds
• Eyelids begin to part and
eyes open sometimes for
short periods of time
• Skin is covered with
protective coating called
vernix
• Baby is able to hiccup
Month 7
• Third Trimester
At the end of 7 months:
• Baby is 14 to 16 inches long
• Weight is about 2 1/2 to 3 1/2
pounds
• Taste buds have developed
• Fat layers are forming
• Organs are maturing
• Skin is still wrinkled and red
• If born at this time, baby will
be considered a premature
baby and require special care
•
Month 8
•
•
•
•
•
•
•
•
•
•
Third Trimester
At the end of 8 months:
Baby is 16 1/2 to 18 inches long
Weight is about 4 to 6 pounds
Overall growth is rapid this month
Tremendous brain growth occurs
at this time
Most body organs are now
developed with the exception of
the lungs
Movements or "kicks" are strong
enough to be visible from the
outside
Kidneys are mature
Skin is less wrinkled
Fingernails now extend beyond
fingertips
Month 9
Third Trimester
At the end of 9 months:
• Baby is 19 to 20 inches
long
• Weight is about 7 to 7 1/2
pounds
• The lungs are mature
• Baby is now fully
developed and can survive
outside the mother's body
• Skin is pink and smooth
• Baby settles down lower in
the abdomen in
preparation for birth and
may seem less active
AMNIOTIC FLUID
• Clear, yellowish fluid surrounding the
developing fetus.
• Average amount 1000 ml.
• Having < 300ml – Oligohydramnios,
associated with fetal renal
abnormalities.
• Having > 2 L – Hydramnios,
associated with GI and other
malformations.
AMNIOTIC FLUID
• Protects Fetus
• Controls Temperature
• Supports Symmetrical Growth
• Prevents Adherence to amnion
• Allows Movement
• Source of oral fluid
• Acts as a excretion-collection
repository
UMBILICAL CORD
Connecting link between fetus and
placenta.
• Transports oxygen and nutrients to fetus
from the placenta and returns waste
products from the fetus to the placenta.
• Contains: 2 arteries and 1 vein
supported by mucoid material (wharton’s
jelly) to prevent kinking and knotting.
• Contains NO pain receptors.
PLACENTA
PLACENTA
mom
Baby
MOM
Baby
Schematic drawing of placenta: how it supplies oxygen and nutrition to embryo and removes waste
products. Deoxygenated blood leaves fetus through the umbilical arteries and enters placenta,
where it is oxygenated. Oxygenated blood leaves placenta through the umbilical vein, which enters
PLACENTA
Produce protein hormones:
• Human chorionic gonadotrophin
(HCG)- 8-10 days past conception, is
basis for pregnancy test
• Progesterone
• Estrogen
• Human Placental Lactogen
PLACENTA
• Sieve/filter – allows smaller particles
through and holds back larger
molecules. Passage of materials in
either direction is effected by:
– Diffusion: gases, water, electrolytes
– Facilitated transfer: glucose, amino
acids, minerals.
– Pinocytosis: movement of minute
particle
PLACENTA
• Mother transmits immunoglobulin G
(IgG) to fetus providing limited
passive immunity.
• Leakage: caused by membrane
defect: may allow maternal and fetal
blood mixing.
VIABILITY
• Capability of fetus
to survive outside
uterus at the
earliest gestational
age - 22-24 weeks
• Survival depends
on:
– Maturity of fetal
central nervous
system
– Maturity of lungs
RESPIRATORY SYSTEM
• Terminal SAC period - 24 Weeks to birth
• Growth of primitive alveoli
• Pulmonary surfactants
produced which act as
wetting agents that prevent
alveolar walls from sticking
• Insufficient surfactant - RDS
• Lecithin/Sphingomyelin-Phospho Lipids
L/S Ratio
30-32 Weeks
35 Weeks
1.2 : 1
2:1 (MATURITY)
CARDIOVASCULAR SYSTEM
• 1st System to
function
• FHR 120-160/Min
• Can hear FHR
with doppler at
10-12 Weeks
FETAL CIRCULATION
• Arteries in umbilical
cord and fetal body
carry deoxygenated
blood.
• Vein in cord and those
in fetal body carry
oxygenated blood
• Ductus venosus
connects umbilical vein
and inferior vena cava;
bypassing portal
circulation.
FETAL CIRCULATION
• Foramen Ovale
allows blood to
flow from right to
left atrium,
bypassing lungs.
• Ductus Arteriosus
allows blood flow
from pulmonary
artery to aorta,
bypassing fetal
lungs;
• HEPATIC SYSTEM
– Liver functions 4-6 weeks
– Full liver function after delivery
• MUSCULO-SKELETAL SYSTEM
– Bones and muscles develop by 4th week
– Fontanels – areas where >2 bones meet
– 7-8 Weeks arms & leg movements
GASTROINTESTINAL
SYSTEM
• Forms during 4th week
• Middle portion of the
intestine projects out into
cord during 5th week.
Returns during 10th week.
If this does not occurOmphalocele present at
birth
• Meconium – Dark green to
black tarry waste
accumulated in the fetal
intestine near term
RENAL SYSTEM
• Kidneys form in 5th week and begin to
function 4 weeks later.
• Voiding into amniotic fluid
• Low volume can show renal dysfunction
• Renal malformation can be diagnosed
in utero.
• GFR is low at birth
NEUROLOGICAL SYSTEM
• Formed from the ectoderm during
the 3rd week
• Respiratory effort
18 1/2 WKS
• Swallowing
12 1/2 WKS
• Sucking
29 WKS
• Fetal movement felt
16-20 WKS
(Quickening)
ENDOCRINE SYSTEM
• Thyroid gland 1st to develop
• Insulin produced at 20 weeks
INTEGUMENTARY SYSTEM
•
•
•
•
7th week – Two layers of cells
Vernix caseosa –Protects skin
Lanugo – Fine hair
10th week – Fingernails, toenails
IMMUNE SYSTEM
• Passive immunity - FROM MOM
• Active immunity - FROM FETUS
MULTIFETAL PREGNANCY
• TWINS
• MULTIFETAL
PREGNANCIES
Teratogens
• Environmental exposures that can
adversely effect the developing fetus
– Maternal Conditions
• Alcoholism, Diabetes, Endocrinopathies,
Phenylketonuria (PKU), Smoking, Nutritional
problems
– Infections Agents
• Rubella, Toxoplasmosis, Syphillis, Herpes Simplex,
Cytomegalic Inclusion Disease, Varicella, Venezuelan
Equine Encephalitis
– Mechanical Problems (deformations)
• Amniotic band constrictions, Umbilical Cord
constraint, Disparity in uterine size and uterine
contents
– Chemicals, drugs, radiation, hyperthermia
STAGES OF DEVELOPMENT