Ultrasonography Monitoring: Chorionic sac during embryonic
period placental and fetal size multiple births abnormal
presentations biparietal diameter Uses reflection of very high
frequency sound waves of between 3.5 to 7.0 megahertz (i.e. 3.5 to
7 million cycles per second)
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Fetal Blood Sampling Usually from the scalp, fetal blood pH is
a good indicator of placental gas exchange. In the past, fetal
blood sampling was used only during labor through the mother's open
cervix to test blood from the fetal scalp for oxygenation. Today,
in many perinatal care centers, fetal blood sampling is performed
by specially trained perinatologists as part of diagnosing,
treating, and monitoring fetal problems at various times during
pregnancy.
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Fetal Blood Sampling A fetal blood sample may be taken to:
diagnose genetic or chromosome abnormalities. check for and treat
severe fetal anemia or other blood problems such as Rh disease.
check for fetal oxygen levels. check for fetal infection. give
certain medications to the fetus.
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How is fetal blood sampling performed? A long, thin needle is
inserted into the mother's uterus guided by ultrasound. Blood may
be taken from several sources: blood vessels of the umbilical cord
(also called cordocentesis, funicentesis, or percutaneous umbilical
blood sampling, or PUBS) a fetal blood vessel, usually in the liver
or heart Fetal blood transfusions may also be performed in
this
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used in prenatal diagnosis of chromosomal abnormalities and
fetal infections, in which a small amount of amniotic fluid, which
contains fetal tissues, is extracted from the amnion or amniotic
sac surrounding a developing fetus, and the fetal DNA is examined
for genetic abnormalities. Little amniotic fluid present prior to
12th week of gestation Amniocentesis also referred to as amniotic
fluid test or AFT
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Chorionic Villus Sampling chromosomal abnormalities etc. The
advantage of CVS is that it can be carried out 10-13 weeks after
the last period, earlier than amniocentesis (which is carried out
at 16-20 weeks).
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Alpha-Fetoprotein Assay AFP is a glycoprotein synthesized in
the fetal liver and yolk sac. The fetus normally excretes AFP into
its urine, hence into the amniotic fluid. High levels may also be
present due to: open neural tube defect open abdominal wall defect
skin disease or other failure of the interior or exterior body
surface. Various forms of tumours
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Factors Affecting Fetal Growth
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Placental Insufficiency Placental defects effectively reduce
available surface area reduced uteroplacental blood flow may also
occur due to maternal hypotension or renal disease.
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Multiple Pregnancy Individuals of multiple births usually weigh
considerably less in the third trimester placenta may not be able
to supply the total requirements for multiple births
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Small Babies Low birth weight: < 2,500g Premature: < 37
weeks of gestation Small for Date: Smaller than expected for
age
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Maturity
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Gradient vs Indicator Maturity Gradients assessment of the
relative rates of development of parts or structures of the body
Maturity Indicators Some characteristic of the body that has
distinct stages of development that all normally developing
children will pass through
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Maturity Gradient
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17 Upper Arm Maturity Gradient
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Three 13 year old Girls
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Three 14 year old Boys
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Bigness vs Maturity Do not confuse size with maturation Obesity
often associated with advanced maturation skeletally but not in
muscular development
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Maturity Indicators Age of Peak Height Velocity Skeletal Age
Dental Age Menarche Secondary Sexual Characteristics
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Skeletal Age
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Closer relationship of Age at Menarche with Skeletal Age (SA)
than Chronological Age (CA)