Page 429 - Essential Haematology

Chapter 30 Pregnancy and neonatal haematology / 415

fall to below normal in 20 – 30% of pregnancies and The platelet count falls for a day or two after
low values are sometimes the cause of diagnostic delivery and then recovers rapidly. Th e HELLP
confusion. syndrome (haemolysis, elevated liver enzymes and
low platelets) is a subtype of this category. It is
associated with prolongation of the prothrombin
Thrombocytopenia
time (PT) and activated partial thromboplastin

The platelet count typically falls by approximately time (APTT).
10% in an uncomplicated pregnancy. In approxi- Idiopathic (autoimmune) thrombocytopenic
mately 7% of women this fall is more severe and purpura (see p. 334 ) In pregnancy, ITP repre-
can result in thrombocytopenia (platelet count sents a particular problem, both to the mother and
9
< 140 × 10 /L). In over 75% of cases this is mild to the fetus, as the antibody crosses the placenta and
and of unknown cause, a condition referred the fetus may become severely thrombocytopenic.
to as incidental thrombocytopenia of pregnancy . Like all adults, pregnant women with ITP and
9
Approximately 21% of cases are secondary to platelet counts > 50 × 10 /L do not usually need
a hypertensive disorder and 4% are associated treatment. Treatment is required for women with
9
with immune thrombocytopenic purpura (ITP; platelet counts < 10 × 10 /L and for those with
9
Fig. 30.2 ). platelet counts of 10 – 30 × 10 /L who are in their
Incidental thrombocytopenia of preg- second or third trimester or who are bleeding.

nancy This is a diagnosis of exclusion and is Treatment is with steroids, intravenous immu-
usually detected at the time of delivery. Th e platelet noglobulin G (IgG), rituximab and splenectomy as
9
count is always > 70 × 10 /L and recovers within 6 appropriate.
weeks. No treatment is required and the infant is At delivery, umbilical vein blood sampling or
not aff ected. fetal scalp vein sampling to measure the fetal plate-

Thrombocytopenia of hypertensive disor- let count may be offered although their exact role
ders This is variable in severity but the platelet is unclear. In general, caesarean section is not

9
count rarely falls to < 40 × 10 /L. It is more severe indicated when the maternal platelet count is
9
when associated with pre - eclampsia and if severe the > 50 × 10 /L unless the fetal platelet count is known
9
primary treatment is as rapid delivery as possible. to be < 20 × 10 /L. Platelet transfusion may be
80
%
60

40

20

0
Incidental Hypertensive Immune Others
thrombocytopenia disorders disorders

Figure 30.2 Causes of thrombocytopenia during pregnancy.