Identification of feto-maternal haemorrhage around labour using flow cytometry immunophenotyping

To determine the normal range of feto-maternal haemorrhage (FMH) due to labour, and to investigate if the type of delivery might influence the volume of FMH.

In a prospective cohort trial setting we studied 346 women in their 3rd trimester of gestation. Women were classified according to the type of delivery: vaginal, instrumental and caesarean section. Fetal erythrocytes in maternal blood were measured by flow cytometry immunophenotyping using a fluorochrome-conjugated monoclonal antibody against fetal haemoglobin. For each woman, two blood samples were studied; one pre-labour and one post-labour. The difference between FMH values obtained post- and pre-delivery was established as FMH due to delivery.

FMH due to labour ranged between <0.01 and 25.19 ml, being <1.15 ml in 96.13% of cases. This value was established as the upper limit of normal FMH due to delivery. No statistical significance was found between the volume of FMH and type of delivery. Analyzing distributions of groups, most data followed a normal distribution, apart from some patients who had higher volume of FMH. Among these patients caesarean sections showed a higher FMH volume, with statistically significant differences between vaginal deliveries and caesarean sections (p=0.001), and between instrumental deliveries and caesarean sections (p=0.008).

FMH due to labour is small. The route of delivery could not be established as a risk factor for FMH but caesarean section increases the risk of suffering a higher amount of transplacental bleeding.