·
Estrogen
activates oxytocin secretion and myometrial
gap junction formation.
Progesterone
suppresses production of maternal lymphocytic cytokines, which contribute to
immune rejection of the fetus. Progesterone produced by the corpus luteum is essential for pregnancy maintenance until the
eighth week. Progesterone suppositories are prescribed during the first 8 weeks
of gestation in women with suspected corpus luteum
deficiency.
hCG
regulates fetal testicular testosterone production, which is critical for the
development of male external genitalia. Elevated hCG is the most sensitive serum marker for Down
syndrome. Abnormally high levels of hCG
are seen in multiple gestation (twins).
hPL induces
lipolysis, which provides energy for the mother in
the form of fatty acids. hPL
also provides energy for the fetus by elevating ketone
levels.
Prolactin is produced not only by the decidual tissue of the uterus, but also by the maternal and
fetal pituitary glands. Lactation does not occur during pregnancy because
estrogen inhibits the action of prolactin on the
breast.
Low levels of estriol are associated with placental
sulfatase deficiency.
Anencephaly contributes to lack of ACTH production; therefore, the fetal adrenal
cortex is not stimulated properly to convert pregnenolone
to DHEA and DHEAS, which are essential in the production of estriol.
·
The differential diagnosis of recurrent spontaneous abortions
in women includes deficiencies of protein C and
protein S, and the presence of the lupus
anticoagulant, which is part of the anti-phospholipid
syndrome.
·
It is not
uncommon for patients with osteogenesis imperfecta type II—the
lethal form—to have dozens of fractures before birth. Osteogenesis imperfecta types I
and III, which are compatible with life and may cause blue scleras (type I),
are often not detectable before birth.
·
Anencephaly is, of course, incompatible with life and is the only condition
for which a termination of pregnancy is generally permissible at any
gestational age.
The incidence of neural tube defects in the general population is
approximately 1.4 to 2.0/1000. It is a multifactorial
defect and is not influenced by maternal age. Women who have a previously affected child have a neural tube defect recurrence
risk of about 3 to 4%. A chorionic villus
sampling will determine a fetus’s chromosomal makeup but will give no
information regarding AFP levels or risk for a neural tube defect. Hyperthermia
at the time of neural tube formation in the embryo, as can occur with maternal
fever or sauna baths, can increase the relative risk of a neural tube defect up
to sixfold.
·
Vaccines for
measles and mumps are generally considered to be contraindicated in pregnancy
as these are live viruses, although the rubella
vaccine, which is known to have been administered inadvertently to
over 1000 pregnant women, has never caused a
problem and in fact can be used in selected circumstances of exposure.
No cases of congenital
rubella syndrome have been reported in this group of patients.
Administration of rabies vaccine is unaffected by
pregnancy.
Immunization for yellow fever is recommended
before travel to a high-risk area. ( confusion ??)
·
Moderate
consumption of coffee has not
been associated with any fetal risks. Consumption of more than five
cups of coffee a day has been shown to be associated with a slightly increased
risk of spontaneous abortion in some studies. Cocaine
use has been associated with an increased incidence of placental
abruption and a constellation of congenital anomalies (skull defects,
disruptions in urinary tract development, limb defects, and cardiac anomalies).
Marijuana has not been
associated with any adverse fetal effects. Lysergic acid diethylamide (LSD) has not been found to be a human teratogen. Tobacco
use has been associated with a number of adverse pregnancy outcomes including spontaneous
abortion, preterm labor, growth restriction, placental abruption, placenta previa, and attention deficit disorder and behavior and
learning problems.
·
Chorionic villus sampling performed at a
gestational age of less than 9 weeks has been associated with fetal limb
reduction defects.
·
A high level
of hCG
in the second trimester is the most sensitive marker for Down
syndrome. A high level of hCG
in the first trimester is suggestive of molar pregnancy. hCG is part of the quadruple
screen in the second trimester, not the first trimester. A low level of hCG is suggestive of ectopic
pregnancy. hCG stimulates
production of TSH, not TRH, leading to hyperthyroidism.
·
Ultrasound
examination in the first trimester provides the most accurate dating.
Measurement of the crown-rump length (CRL)
is accurate to within 5 to 7 days of the actual gestational age. Second-
and third-trimester ultrasound uses several parameters for determining
gestational age. These parameters include the biparietal diameter (BPD), the femur length (FL), and the
abdominal circumference (AC). In the second trimester, the BPD is
the most accurate but only to within 14 days of the actual gestational
age. Measurements in the third trimester may have an error up to ±21 days
of the actual gestational age.
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