Abstract

Venous thromboembolism (VTE) is a major cause of maternal morbidity and mortality. In the non-pregnant patient D-Dimer testing has a role as a negative predicator of thrombosis. This is not a recognised test in pregnancy as D-Dimer concentration increases progressively from conception until delivery.

The aim of this study was to establish reference values for D-Dimers in the first trimester of normal pregnancy and compare these ranges to the normal non-pregnant range.

D-Dimer measurements were carried out on 164 low risk women carrying singleton pregnancy in their first trimester. Samples were analysed using Bio-pool Auto-Dimer Assay.

Data from a previous study establishing normal (non-pregnant) ranges of D-Dimer using the same assay were compared with data obtained from these 164 pregnant women.1 Table shows the differences observed between the two populations. There is a clear increase in D-Dimer levels for pregnant women, with the 5th and 95th centiles increased to 39 and 500 ng/ml respectively. There was no significant trend of D-Dimer across gestational age in first trimester.

The results support findings from previous studies reporting a progressive increase in D-Dimer levels during normal pregnancy. The recommended cut off in the diagnosis of VTE for pregnant women in the first trimester based on this study is 500 ng/ml rather than 224 ng/ml