Fetomaternal macrotransfusion in the Yorkshire region. 1. Prevalence and obstetric factors

Abstract

The prevalence of fetomaternal macrotransfusion (FMMT), defined as fetomaternal haemorrhage (FMH) greater than or equal to 10 ml, was calculated in a series of 15,724 postpartum Kleihauer tests recorded in six hospitals. The mean prevalence in this retrospective survey, the largest published to date, was 0.83% (SEM 0.22) but values varied according to the technique used to quantify the volume of FMH. A number of obstetric factors that have been suggested as influencing the occurrence and extent of FMMT were examined. The frequencies of these factors in cases with FMMT were compared with those in a control group without FMMT selected from the same population. Manual removal of the placenta (P less than 0.0001) and fetal distress in labour (P less than 0.0001) occurred significantly more frequently in the case group. We are unable to confirm previous reports that other obstetric factors may influence the occurrence and extent of FMMT.