Book of Medical Disorders in Pregnancy - Tintash

maternal circulation. If the child's red
cells are of group A or group B and the
maternal serum contains anti A or anti B,
the antibodies will destroy the invading
red cells quite rapidly so that they have a
limited survival time. This natural
protection is not 100% effective and may
break down once the Rh negative
woman carried an ABO compatible Rh
positive fetus.
Follow-up of mother in antenatal
period - Screening test for antibodies
should be performed early in pregnancy
on sera of all pregnant women since
woman may produce an antibody to any
antigen she lacks. A woman whose serum
does not contain irregular antibody
is on initial testing should be retested in
the second and third trimesters of her
pregnancy. Since optimum conditions
for antigen/antibody interactions vary
quite considerably, screening test must
be done at different temperatures and in
more than one medium i.e. saline and
albumin.
For detection of patients at risk, all patients
at the initial prenatal visit should
have atypical antibody screening, blood
group and Rh. type determination. The
screening test is done even in primigravida
patients to detect previous sensitization
due to conditions not known
by the patient or known but not revealed
to the physician, e.g. abortions, transfusion,
etc. The assessment of patients
for determination of risk is shown in
Flow Sheet 1.
The high risk patients can be screened
by using indirect antiglobulin technique
(indirect Coombs’ test). The titration
should be carried out serially and
frequently during the whole pregnancy.
The critical level of antibody titre
126
reported by most authors is 1:16. No
intrauterine death or severely affected
baby has been reported when the titer
was below 116. However we suggest
that titer of 118 should be adopted.
The policy of determining; antibody titer
at monthly intervals during the first and
second trimester and then fortnightly in
the third trimester is generally accepted.
If the titre is 1 32 or greater, the patient
should be followed by amniotic fluid
analysis, obtained by amniocentesis.
When the serum antibodies are less than
or equal to 1:8 in albumin at 34 weeks of
gestation then there is no chance of a
still-birth before term. If the titre rises to
1:16 at 36 weeks of pregnancy then deliver
the baby. On the other hand when
the titre is less than 1: 16 before 36
weeks of pregnancy and there is a history
of previous stillbirth or exchange
transfusion then amniocentesis should be
done to establish severity of the disease.
Prediction of severity of the Rhesus
disease is only 60% accurate when it is
based on history and antibody titres
alone, but with amniocentesis. it is 95%
accurate.
Effective method of predicting and
evaluating the severity of hemolytic
disease of the newborn is therefore by
amniocentesis. TED to spectrophotometric
scanning. Complications include
maternal infection, placental injury, fetal
injury and even, premature induction of
labour.
Once started, amniocentesis should be
repeated at 1 to 3 weeks intervals. With
antibodies titre greater than 1:16 and
pregnancy less than 32 weeks there is
10% chance of still-birth before term and