Book of Medical Disorders in Pregnancy - Tintash

continues after the end of the uterine
contraction. These decelerations are
always pathological and occur as a result
of fetal hypoxia.
Variable deceleration - They do not
have any set pattern of onset. Their
relationship contraction is not fixed.
Even the wave is variable in shape. If
variable exists for longer period, they
indicate fetal distress.
Oxytocin stress test - This test is based
on electronic monitoring of the fetal
heart rate and its response to a series of
uterine contractions induced by weak
oxytocin infusion. The change in fetal
heart rate in response to induced uterine
activity adequately demonstrates the
placental and fetal reserves. When there
is lack of placental reserve to maintain
adequate oxygenation during this test, it
indicates that the fetus is unable to
tolerate the stress of normal labor.
Biochemical assessment - Biochemical
assessment of the fetus in utero can not
be carried out without adopting invasive
techniques. The fetal blood can be
obtained by scalp puncture and reveal
PH, P02, pe02 and base excess. The fall
in pH and base excess shows pyruvate
and lactate production from glycogen
stores by anaerobic metabolism. PH
values below 7.2 reflect severe fetal
hypoxia. Single pH value is less useful
than serial, as it may reflect maternal
acidosis. PH measurements can be
applied for management in high risk
pregnancies.
Biophysical method:
(Ultrasonography) - proper timing of
delivery in pregnancy com plicated by
high risk factor is required, if better
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outcome of the mother and neonate is to
be expected.
The rate of fetal growth and maturity can
be measured from the fetal biparietal
diameter (details of this technique have
been provided under separate heading on
Ultrasonography
Ultrasonography: This is a noninvasive
procedure that is harmless to both the
fetus and the mother. High frequency
sound waves are utilized to produce
visible images from the pattern of the
echoes made by different tissues and
organs, including the baby in the
amniotic cavity. The developing embryo
can first be visualized at about 6 week’s
gestation. Recognition of the major
internal organs and extremities to
determine if any are abnormal can best
be accomplished between 16 to 20
weeks gestation. Although an ultrasound
examination can be quite useful to
determine the size and position of the
fetus, the size and position of the
placenta, the amount of amniotic fluid,
and the appearance of fetal anatomy,
there are limitations to this procedure.
Subtle abnormalities may not be
detected until later in pregnancy, or may
not be detected at all. A good example of
this is Down syndrome (trisomy 21)
where the morphologic abnormalities are
often not marked, but only subtle, such
as nuchal thickening.
The biparietal diameter increases by
about 1.6 to 1.8 mm per week. This
technique provides reproducible physical
assessment of intrauterine growth and
can be correlated with biochemical and
endocrinological technique for assessing
fetal health. Other indications for use of
ultrasound scan will be discussed in
chapter on imaging in pregnancy.