A randomised controlled trial of placental cord drainage to reduce feto-maternal transfusion

To determine whether placental drainage via the umbilical cord prior to placental delivery reduces the size of feto-maternal transfusion and thus the chance of rhesus isoimmunisation in rhesus negative women.

A randomised controlled trial conducted in a tertiary hospital setting in the UK compared 18 rhesus negative women who had placental drainage (10 caesarean section and 8 vaginal deliveries) with 18 rhesus negative women where the cord remained clamped until placental delivery (8 caesarean section and 10 vaginal deliveries). Maternal venous blood samples were taken before delivery and at a mean of 142 min after delivery of the placenta, and analysed using flow cytometry to calculate the size of the feto-maternal transfusion. The statistical analysis was performed using SPSS Version 13 statistical software. The main outcome measure was the quantification of the volume of fetal cells in the maternal circulation before and after delivery.

In the 72 specimens taken, 40 demonstrated measurable amounts of fetal cells in the maternal circulation. In the 18 women who had placental drainage, the mean (SD) size of the feto-maternal transfusion was 0.50 ml (0.79) before and 0.39 ml (0.58) after delivery. In the 18 women who had a clamped cord, the mean (SD) feto-maternal transfusion was 0.46 ml (0.84) before and 0.78 ml (1.1) after delivery. There was no significant difference between the net feto-maternal transfusions in the two groups (Mann-Whitney U 122.5, p 0.19).

Placental drainage does not reduce the amount of feto-maternal transfusion and this method of placental delivery is not recommended to reduce feto-maternal transfusion.