Role of Placenta Parameters in Predicting Significant Feto-Maternal Haemorrhage

Purpose: Feto-maternal haemorrhage (FMH) is a complication of pregnancy and large FMH may lead to life-threatening anaemia in the fetus or newborn. In addition, exposure of Rhesus (Rh) D negative women to small amounts of fetal Rh D positive red cells during pregnancy or delivery may result in sensitization with its attendant problems of isoimmunisation. In most cases, the cause of FMH IS unknown. Through this study, we sought to determine if placental weight & diameter have any direct relationship with incidence and severity of FMH. Methods: This was a prospective study of parturients for presence of fetal red cells in the maternal blood circulation. The prepared slide was processed as in the acid elution test described by Kleihauer-Betke. The FMH was calculated using Mollison formula. Baseline data included maternal biodata, blood group, Rh D factor, placenta weight and diameter. Data generated were analysed with Frequency tables, cross-tabulations and Odd ratio and confidence intervals as appropriate. Results: Three hundred parturients were studied. However, only two hundred and ninety-five parturients were analysed, with five excluded due to lysed blood samples. A total of 52 parturients (17.63%) had demonstrable FMH, of which 8 (2.71%) were large FMH (>15 ml foetal cells). Both the placenta weight (P < 0.005) and diameter (P < 0.042) were significantly associated with incidence of FMH, more with placenta weight than diameter. Incidence of demonstrable FMH was 24.12% (48/199) in the group with placenta weight greater than 500 g, in contrast to 4.17% (4/96) in the group with weight of placenta below or equal to 500 g. All the 8 parturients with large FMH had placenta weights greater than 500 g. Placenta diameters were greater than 22 cm in 41/197 (20.81%) who had demonstrable FMH, compared with 11/98 (11.23%) whose diameter was less than 22 cm. Conclusion: Both the placenta weight and diameter are significant predictors of FMH in parturients. However, placenta diameter appears to be a minor predictor. These are factors that can be assessed antenatally by ultrasonography and in conjunction with other known obstetric factors, may possibly be considered in risk-based scoring system for predicting feto-maternal haemorrhage.