Fetomaternal haemorrhage (FMH) is defined as passage of fetal blood into maternal circulation. Threshold volumes of 80 and 150 ml have been used to describe large and massive FMH respectively. Its true incidence is difficult to determine as it is probably under-reported. It is difficult to predict as most cases occur spontaneously. Maternal complaints of reduced fetal movements in association with CTG abnormalities may lead one to suspect FMH.
Following a literature review a threshold volume of 80 ml for large FMH was chosen. 12 cases of large FMH from 2005 to 2010 at Cork Maternity Services were identified. FMH volumes ranged from 84 to 150 ml (median 113 ml). When expressed in terms of birth weight this ranged from 24.7 to 55.8 ml/kg (median 41.3 ml/kg). Six of these cases presented with reduced fetal movements while the CTG was described as sinusoidal in three cases. The majority (n=10) were detected in the postnatal period, indicating that there was not a high index of suspicion for this condition among attending staff. No risk factors for development of FMH were identified in this population. There were three poor outcomes – one intrauterine death and two cases of hypoxic ischaemic encephalopathy. No association was found between outcome and FMH volume.
Although large FMH is rare, it does occur and its consequences can be devastating. As it mostly occurs without any obvious precipitating factors its diagnosis is often not made in a timely manner. A high index of suspicion with prompt investigation and appropriate management may improve perinatal outcome.
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