a1 Bristol Maternity Hospital, Bristol, UK
Autoimmune thrombocytopenia (ITP)
1) The risks to mother and fetus have previously been overstated.
2) There is no maternal test which will accurately determine fetal thrombocytopenia.
3) The only reliable test for fetal thrombocytopenia is cordocentesis – this carries a higher morbidity than that of fetal intracerebral haemorrhage from ITP.
4) Contrary to received wisdom, there is no evidence that, even for the most severely thrombocytopenic infant, abdominal delivery protects against intracranial haemorrhage.
5) Management therefore involves keeping the maternal platelet count above 50 × 1091 and choosing the route of delivery on normal obstetric grounds.
1) Alloimmune thrombocytopenia is commoner than hitherto believed (0.15% all neonates).
2) The fetal risks are considerable: intracranial haemorrhage occurs in 4% of cases antenatally and in 10% in labour. The risks are virtually confined to those with a platelet count of less than 30 × 109l−1.
3) Cordocentesis is justified for the ‘at risk’ fetus; fetal immunoglobulin or platelet therapy can be given.
4) When the fetal platelet count is below 50 × 109l−1, abdominal delivery should be planned.
5) A maternal screening test for neonatal alloimmune thrombocytopenia exists (lack of P1A1 antigen).
c1 James Browning, Lecturer in Obstetrics, Bristol Maternity Hospital, Bristol BS2 8EG, UK.