Fetal development Morphological/ physiological/ biochemical aspect

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Transcript Fetal development Morphological/ physiological/ biochemical aspect

Fetal development
Morphological/ physiological/
biochemical aspect
and clinical correlation
รองศาสตราจารย์ นายแพทย์ อติวทุ ธ กมุทมาศ
Morphological aspect
and clinical correlation
Dating of pregnancy
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Obstetricians : Menstrual age/ gestational
age : LMP (first day) = 2 wk before
ovulation/ fertilization , 3 wk before
implantation of blastocyst
Embryologists : ovulation age/
postconception age
Clinical correlation
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EDC = LMP + 7 days – 3 months
Pregnant duration = 40 wk/ 280 d/ 9 1/3 mo
3 trimesters : 1 / 2 / 3
Before 28 wk = abortion (USA < 20 wk)
28 – 36 wk = preterm
37 – 42 wk = term
> 42 wk = postterm
The ovum, zygote, blastocyst
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Ovulation
Fertilization of the ovum
Formation of free blastocyst
Implantation of the blastocyst
Clinical correlation
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Time to test for pregnancy : serum hCG = 3
wk (gestational age) (not for UPT)
Implantation bleeding (Hartman’s sign) : 3
wk GA
Wrong date by implantation bleeding
Not include in threatened abortion
The embryo
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At the beginning of the 3rd wk after
ovulation (3 wk OA/ 5 wk GA)
Embryonic disc is well defined
Body stalk is differentiated
The chorionic sac = 1 cm
Clinical correlation
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Time for UPT positive
Begin to detect by ultrasound : vaginal
probe/ abdominal probe
GA calculated by mean sac diameter
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Sac 1 cm = 5 wk GA
Sac 2 cm = 6 wk GA
Sac 3 cm = 7 wk GA
The embryo (cont)
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4th wk Ovulation age (6 wk GA)
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chorionic sac = 2-3 cm in diameter
embryo = 4-5 mm in length
fetal heart beat = movement
8 wk GA
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Embryo = 22-24 mm in length
Head found and quite large
Clinical correlation
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GA calculated by CRL (crown rump length)
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CRL (cm) + 6.5 = GA (wk)
If bleeding = threatened abortion/ blighted ovum/
dead embryo can be diagnosed by ultrasound at
this time (after 6 wk GA)
GA by CRL is accurate as ± 4.7 days
The fetus
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8 wk after ovulation (GA 10 wk)
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4 cm long
Major structures are formed
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12 weeks fetus
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CRL = 6-7 cm
Centers of ossification appear
Fingers and toes are differentiated
Nails present
Rudiments of hair appear
External genitalia begins to show
Clinical correlation
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Uterus begins to be palpable (as 1/3 above
pubic symphysis)
Morning sickness is improved
16 weeks fetus
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CRL = 12 cm
Wt = 110 gm
Clinical correlation
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Uterus 2/3 above pubic symphysis
Doing well
Quickening
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Primigravida = 18-20 wk
Multiparity = 16-18 wk
Fetal heart beat detected by stethoscope
Fetal gender detected by ultrasound
20 weeks fetus
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Mid point of pregnancy
Wt = 300 gm
Fetal skin has become less transparent
Lanugo hairs cover entire body
Scalp hair visible
Clinical correlation
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Uterus at umbilicus
Midpoint of pregnancy : size of uterus is
mostly reliable regardless of factors such
as thickness of abdominal wall, experience
of the examiners
24 weeks fetus
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Wt = 630 gm
Skin : wrinkled
Fat : deposit
Eyebrows / eyelashes recognizable
Clinical correlation
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Uterus size = 1/4 above umbilicus (24 cm
by Jeminez)
If delivered = baby (newborn/ infant)
attempt to breathe , but almost always dies
shortly after birth
28 weeks fetus
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CRL = 25 cm
Wt = 1100 gm
Skin : red, covered with vernix caseosa
Pupillary membrane has just disappeared
from the eyes
Clinical correlation
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Uterus size = 2/4 above umbilicus, 28 cm
Viable period
Infant born : limbs quite energetic, cries
weakly, survive with expert care (NICU)
32 weeks fetus
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28 cm long
1800 gm
Skin still red and wrinkle
36 weeks fetus
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32 cm
2500 gm
More deposition of subcutaneous fat :
wrinkle is lost
40 weeks fetus
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36 cm
3400 gm (average)
Full term (37 - 42 weeks GA)
After 42 weeks
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Postterm
Skin become wrinkle again
Amniotic fluid decreased
Placental dysfunction
Fetal compromised
Fetal death in utero/ still birth
Fertilization
Fertilized ovum
Blastocyst formation
Embryo development
Biochemical aspect
and clinical correlation
Nutrition of the fetus
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First 2 months : embryo consists almost
entirely of water
In later months : relatively more solids are
added
Because small amount of yolk : most
nutrients early obtained from mother
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During the first few days after implantation :
the nutrition of the blastocyst arises directly
from the interstitial fluid of the endometrium
and from the surrounding maternal tissue
Within the next week : intervillous spaces
are formed, lacunae filled with maternal
blood
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Maternal diet is the source of the nutrients
supplied to the fetus
If mother is fasting : glucose is released
from glycogen but storage is not adequate
Cleavage of triacylglycerols (stored in
adipose tissue) provide the mother with
energy in the form of free fatty acid
Glucose
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Facilitated diffusion
A major nutrient for growth and energy of
the fetus
hPL : blocking the peripheral uptake and
utilization of glucose by maternal tissue
while promoting the mobilization and
utilization of free fatty acid
Lactate
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Transports across the placenta by
facilitated diffusion
Co-transport with hydrogen ion : lactate is
probably transported as lactic acid
Beware of lactic acidosis
Free fatty acid and triglycerides
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Neutral fat (triglycerides) does not cross the
placenta
Glycerol : cross the placenta
The apoprotein and cholesterol esters of LDL are
hydrolyzed by lysosomal enzymes in trophoblasts
: and give
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Cholesterol for progesterone synthesis
Free amino acids (including essential amino acids)
Essential fatty acid
Amino acid
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By the use of LDL
Also directly cross the placenta by diffusion
Proteins and other large molecules
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Larger proteins (ie albumin) : limited
transfer across the placenta
Globulin (IgG) cross the placenta in major
amounts
IgM : increased amount is found only fetal
infection in utero
Iron and trace elements
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Active transport
Clinical correlations
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Iron : active transport ; maternal iron
deficiency anemia if no additional intake ; it
is recommended to supplement iron in
pregnancy with total 1000 mg throughout
pregnancy (absorbed form) or 6-7 mg/d
(absorbed form) or 30-60 mg/d (elemental
form) in singleton pregnancy
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IgM : indicated fetal infection
Risk of lactic acidosis : becareful in giving
any drugs to pregnant women
Risk of maternal DM and fetal macrosomia
: hPL (human placental lactogen),
glucagon, insulinase / glucose transport is
easily by facilitated diffusion
Physiological aspect
and clinical correlation
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Fetal physiology mostly not the same as
the newborn and moreover , the human
adult
Fetal circulation
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Three major shunts
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Ductus venosus
Foramen ovale
Ductus arteriosus
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All nutrient materials deliver from placenta
to fetus via umbilical vein
Single umbilical vein carries oxygenated ,
nutrient bearing blood
IVC consists of an admixture of arterial likeblood (more oxygenation than SVC)
IVC blood to heart then directly through
foramen ovale into left atrium
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Then into left ventricle then eject to 2 vital
structures : the heart and the brain
Bypass pulmonary circulation
Venous blood from SVC : into right
ventricle then to pulmonary trunk and
through ductus arteriosus into the
descending aorta
Clinical correlation
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Umbilical cord : 2 arteries / 1 vein ;
abnormality can be detected such as single
umbilical artery and associated with fetal
KUB anomaly
After birth: the umbilical vessels, ductus
arteriosus, foramen ovale, ductus venosus
normally constrict
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Cord clamp and expansion of lung and
breathing : induce constriction
PDA (patent ductus arteriosus) is common
Umbilical vein : ligamentum teres
Ductus venosus : ligamentum venosum
Fetal blood
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Hematopoiesis is demonstrable first in yolk
sac
The next major site of erythropoiesis is liver
The final site : bone marrow
The fetoplacental blood volume at term =
120 mg/kg of infant weight
Clinical correlation
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Embryonic hemoglobin = Gower 1 (€2/r2)
and Gower 2 (€2/α2)
Fetal hemoglobin = Hb F (α2/r2)
β thalassemia : no symptoms in utero but
symptoms will be present after birth due to
lack of Hb A (α2/β2)
Respiratory system
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Fetal breathing : enhance expansion of the
lung, distended alveoli, and promote
surfactant secretion
Pneumocyte type 2 : surfactant secretion
Surfactant excrete into amniotic fluid
Clinical correlation
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Oligohydramnios : lung hypoplasia
Lung maturity testing : amniotic fluid (from
amniocentesis) for shake test, L:S ratio,
phosphatidylglecerol level
Respiratory distress syndrome (RDS) found
more commonly in preterm birth due to
surface inadequacy
Conclusion
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To know embryology : to understand “why”
the infants are in trouble and “how” to treat
them
Clinical correlation in practice has related to
morphological/ biochemical/ physiological
aspects in fetal development
Thank you for your attention