Book of Medical Disorders in Pregnancy - Tintash

Chapter No: 9
RHESUS DISEASE IN PREGNANCY
This disease is produced by
isoimmunization to D antigen of the Rh.
System and is the commonest form of
sensitization; however other antigens of
the Rh. system (Cc Ee) also cause
sensitiza-tion in a significant number of
cases.
Fig 9.1: Showing process of
immunization in women’s body by the
Rh positive foetus.
Incidence - It has been estimated that 15
percent women are Rh negative of which
3 per cent will marry Rh negative men
and hence have no sensitization, will
occur 5 percent will marry homozygous
Rhesus positive men and have 50 per
cent chance of having Rh sensitization, 7
per cent will marry heterozygous Rhesus
positive men and have 1: 15 chances of
Rh. sensitization, as some babies will be
Rh. negative and some Rhesus positive.
The incidence of erythroblastosis foetalis
is 1: 200 pregnancies i.e. 0.5 per cent·
and accounts for 15 per cent of still
births.
First child has 90% chance of spontaneous
survival. Second child has 70%
chance of spontaneous survival. ABO incompatibility
is almost 100% protective.
However, in mothers where ABO
124
compatibility is present between her and
her baby, at least 10% of such mothers
will develop antibodies in their blood.
Nearly 90% cases of isoimmunization
are due to antigen D while others are due
to capital C, E, Duffy, Kell and Lewis.
Mechanism - When Rh. Negative woman
is exposed to an antigen she does
not possess because she is pregnant with
Rh. positive baby who possesses antigen
D. Antibodies which are gammaglobulin
in nature .are produced in her serum.
Antibodies – There are two types of
antibodies which are formed in response
to Rh. antigen; 19S which are IgM are
formed first these are of large size and
hence do not cross the placenta, later on
7S which are IgG are produced. Usually
they appear after 4 months, they are of
smaller size and cross the placenta and
are responsible for immune reactions.
They can be detected in the maternal
serum by the Coombs’ antiglobulin technique.
These antibodies attack the fetal red
blood cells containing antigen on their
walls. The cells are rapidly destroyed in
the spleen and liver and result in fetal
anemia. When the anemia is severe, congestive
heart failure develops lea-ding to
hydrops fetalis. This can happen as early
as twenty weeks of Pregnancy. When the
hemolysis is not so severe this results in
hemolytic disease of the newborn.
Anaemia:
Which is the greatest danger in utero,
can be corrected by transfusion soon
after delivery. During pregnancy fetal